Merge pull request 'hm-inference' (#6) from hm-inference into master

Reviewed-on: #6

README.md

@@ -15,20 +15,20 @@ caller to specify which methods should be compiled). After type checking, the
 compiler would analyse the set of functions/classes that are used and perform
 code generation.
 
-
-Symbol resolver:
-- Str -> Nac3Type
-- Str -> Value
-
 value could be integer values, boolean values, bytes (for memcpy), function ID
 (full name + concrete type)
 
 ## Current Plan
 
-1. Write out the syntax-directed type checking/inferencing rules. Fix the rule
-   for type variable instantiation.
-2. Update the library dependencies and rewrite some of the type checking code.
-3. Design the symbol resolver API.
-4. Move tests from code to external files to cleanup the code.
+Type checking:
+
+- [x] Basic interface for symbol resolver.
+- [x] Track location information in context object (for diagnostics).
+- [ ] Refactor old expression and statement type inference code. (anto)
+- [ ] Error diagnostics utilities. (pca)
+- [ ] Move tests to external files, write scripts for testing. (pca)
+- [ ] Implement function type checking (instantiate bounded type parameters),
+    loop unrolling, type inference for lists with virtual objects. (pca)
+
 
 

nac3core/Cargo.toml

@@ -7,5 +7,13 @@ edition = "2018"
 [dependencies]
 num-bigint = "0.3"
 num-traits = "0.2"
-inkwell = { git = "https://github.com/TheDan64/inkwell", branch = "master", features = ["llvm10-0"] }
+inkwell = { git = "https://github.com/TheDan64/inkwell", branch = "master", features = ["llvm11-0"] }
 rustpython-parser = { git = "https://github.com/RustPython/RustPython", branch = "master" }
+itertools = "0.10.1"
+crossbeam = "0.8.1"
+parking_lot = "0.11.1"
+rayon = "1.5.1"
+
+[dev-dependencies]
+test-case = "1.2.0"
+indoc = "1.0"

nac3core/rustfmt.toml

@@ -0,0 +1 @@
+ use_small_heuristics = "Max"

nac3core/src/codegen/expr.rs

@@ -0,0 +1,527 @@
+use std::{collections::HashMap, convert::TryInto, iter::once};
+
+use super::{get_llvm_type, CodeGenContext};
+use crate::{
+    symbol_resolver::SymbolValue,
+    top_level::{DefinitionId, TopLevelDef},
+    typecheck::typedef::{FunSignature, Type, TypeEnum},
+};
+use inkwell::{
+    types::{BasicType, BasicTypeEnum},
+    values::BasicValueEnum,
+    AddressSpace,
+};
+use itertools::{chain, izip, zip, Itertools};
+use rustpython_parser::ast::{self, Boolop, Constant, Expr, ExprKind, Operator};
+
+impl<'ctx, 'a> CodeGenContext<'ctx, 'a> {
+    fn get_subst_key(&mut self, obj: Option<Type>, fun: &FunSignature) -> String {
+        let mut vars = obj
+            .map(|ty| {
+                if let TypeEnum::TObj { params, .. } = &*self.unifier.get_ty(ty) {
+                    params.borrow().clone()
+                } else {
+                    unreachable!()
+                }
+            })
+            .unwrap_or_default();
+        vars.extend(fun.vars.iter());
+        let sorted = vars.keys().sorted();
+        sorted
+            .map(|id| {
+                self.unifier.stringify(vars[id], &mut |id| id.to_string(), &mut |id| id.to_string())
+            })
+            .join(", ")
+    }
+
+    pub fn get_attr_index(&mut self, ty: Type, attr: &str) -> usize {
+        let obj_id = match &*self.unifier.get_ty(ty) {
+            TypeEnum::TObj { obj_id, .. } => *obj_id,
+            // we cannot have other types, virtual type should be handled by function calls
+            _ => unreachable!(),
+        };
+        let def = &self.top_level.definitions.read()[obj_id.0];
+        let index = if let TopLevelDef::Class { fields, .. } = &*def.read() {
+            fields.iter().find_position(|x| x.0 == attr).unwrap().0
+        } else {
+            unreachable!()
+        };
+        index
+    }
+
+    fn gen_symbol_val(&mut self, val: &SymbolValue) -> BasicValueEnum<'ctx> {
+        match val {
+            SymbolValue::I32(v) => self.ctx.i32_type().const_int(*v as u64, true).into(),
+            SymbolValue::I64(v) => self.ctx.i64_type().const_int(*v as u64, true).into(),
+            SymbolValue::Bool(v) => self.ctx.bool_type().const_int(*v as u64, true).into(),
+            SymbolValue::Double(v) => self.ctx.f64_type().const_float(*v).into(),
+            SymbolValue::Tuple(ls) => {
+                let vals = ls.iter().map(|v| self.gen_symbol_val(v)).collect_vec();
+                let fields = vals.iter().map(|v| v.get_type()).collect_vec();
+                let ty = self.ctx.struct_type(&fields, false);
+                let ptr = self.builder.build_alloca(ty, "tuple");
+                let zero = self.ctx.i32_type().const_zero();
+                unsafe {
+                    for (i, val) in vals.into_iter().enumerate() {
+                        let p = ptr.const_in_bounds_gep(&[
+                            zero,
+                            self.ctx.i32_type().const_int(i as u64, false),
+                        ]);
+                        self.builder.build_store(p, val);
+                    }
+                }
+                ptr.into()
+            }
+        }
+    }
+
+    pub fn get_llvm_type(&mut self, ty: Type) -> BasicTypeEnum<'ctx> {
+        get_llvm_type(self.ctx, &mut self.unifier, self.top_level, &mut self.type_cache, ty)
+    }
+
+    fn gen_call(
+        &mut self,
+        obj: Option<(Type, BasicValueEnum<'ctx>)>,
+        fun: (&FunSignature, DefinitionId),
+        params: Vec<(Option<String>, BasicValueEnum<'ctx>)>,
+        ret: Type,
+    ) -> Option<BasicValueEnum<'ctx>> {
+        let key = self.get_subst_key(obj.map(|(a, _)| a), fun.0);
+        let defs = self.top_level.definitions.read();
+        let definition = defs.get(fun.1 .0).unwrap();
+        let val = if let TopLevelDef::Function { instance_to_symbol, .. } = &*definition.read() {
+            let symbol = instance_to_symbol.get(&key).unwrap_or_else(|| {
+                // TODO: codegen for function that are not yet generated
+                unimplemented!()
+            });
+            let fun_val = self.module.get_function(symbol).unwrap_or_else(|| {
+                let params = fun.0.args.iter().map(|arg| self.get_llvm_type(arg.ty)).collect_vec();
+                let fun_ty = if self.unifier.unioned(ret, self.primitives.none) {
+                    self.ctx.void_type().fn_type(&params, false)
+                } else {
+                    self.get_llvm_type(ret).fn_type(&params, false)
+                };
+                self.module.add_function(symbol, fun_ty, None)
+            });
+            let mut keys = fun.0.args.clone();
+            let mut mapping = HashMap::new();
+            for (key, value) in params.into_iter() {
+                mapping.insert(key.unwrap_or_else(|| keys.remove(0).name), value);
+            }
+            // default value handling
+            for k in keys.into_iter() {
+                mapping.insert(k.name, self.gen_symbol_val(&k.default_value.unwrap()));
+            }
+            // reorder the parameters
+            let params =
+                fun.0.args.iter().map(|arg| mapping.remove(&arg.name).unwrap()).collect_vec();
+            self.builder.build_call(fun_val, &params, "call").try_as_basic_value().left()
+        } else {
+            unreachable!()
+        };
+        val
+    }
+
+    fn gen_const(&mut self, value: &Constant, ty: Type) -> BasicValueEnum<'ctx> {
+        match value {
+            Constant::Bool(v) => {
+                assert!(self.unifier.unioned(ty, self.primitives.bool));
+                let ty = self.ctx.bool_type();
+                ty.const_int(if *v { 1 } else { 0 }, false).into()
+            }
+            Constant::Int(v) => {
+                let ty = if self.unifier.unioned(ty, self.primitives.int32) {
+                    self.ctx.i32_type()
+                } else if self.unifier.unioned(ty, self.primitives.int64) {
+                    self.ctx.i64_type()
+                } else {
+                    unreachable!();
+                };
+                ty.const_int(v.try_into().unwrap(), false).into()
+            }
+            Constant::Float(v) => {
+                assert!(self.unifier.unioned(ty, self.primitives.float));
+                let ty = self.ctx.f64_type();
+                ty.const_float(*v).into()
+            }
+            Constant::Tuple(v) => {
+                let ty = self.unifier.get_ty(ty);
+                let types =
+                    if let TypeEnum::TTuple { ty } = &*ty { ty.clone() } else { unreachable!() };
+                let values = zip(types.into_iter(), v.iter())
+                    .map(|(ty, v)| self.gen_const(v, ty))
+                    .collect_vec();
+                let types = values.iter().map(BasicValueEnum::get_type).collect_vec();
+                let ty = self.ctx.struct_type(&types, false);
+                ty.const_named_struct(&values).into()
+            }
+            _ => unreachable!(),
+        }
+    }
+
+    fn gen_int_ops(
+        &mut self,
+        op: &Operator,
+        lhs: BasicValueEnum<'ctx>,
+        rhs: BasicValueEnum<'ctx>,
+    ) -> BasicValueEnum<'ctx> {
+        let (lhs, rhs) =
+            if let (BasicValueEnum::IntValue(lhs), BasicValueEnum::IntValue(rhs)) = (lhs, rhs) {
+                (lhs, rhs)
+            } else {
+                unreachable!()
+            };
+        match op {
+            Operator::Add => self.builder.build_int_add(lhs, rhs, "add").into(),
+            Operator::Sub => self.builder.build_int_sub(lhs, rhs, "sub").into(),
+            Operator::Mult => self.builder.build_int_mul(lhs, rhs, "mul").into(),
+            Operator::Div => {
+                let float = self.ctx.f64_type();
+                let left = self.builder.build_signed_int_to_float(lhs, float, "i2f");
+                let right = self.builder.build_signed_int_to_float(rhs, float, "i2f");
+                self.builder.build_float_div(left, right, "fdiv").into()
+            }
+            Operator::Mod => self.builder.build_int_signed_rem(lhs, rhs, "mod").into(),
+            Operator::BitOr => self.builder.build_or(lhs, rhs, "or").into(),
+            Operator::BitXor => self.builder.build_xor(lhs, rhs, "xor").into(),
+            Operator::BitAnd => self.builder.build_and(lhs, rhs, "and").into(),
+            Operator::LShift => self.builder.build_left_shift(lhs, rhs, "lshift").into(),
+            Operator::RShift => self.builder.build_right_shift(lhs, rhs, true, "rshift").into(),
+            Operator::FloorDiv => self.builder.build_int_signed_div(lhs, rhs, "floordiv").into(),
+            // special implementation?
+            Operator::Pow => unimplemented!(),
+            Operator::MatMult => unreachable!(),
+        }
+    }
+
+    fn gen_float_ops(
+        &mut self,
+        op: &Operator,
+        lhs: BasicValueEnum<'ctx>,
+        rhs: BasicValueEnum<'ctx>,
+    ) -> BasicValueEnum<'ctx> {
+        let (lhs, rhs) = if let (BasicValueEnum::FloatValue(lhs), BasicValueEnum::FloatValue(rhs)) =
+            (lhs, rhs)
+        {
+            (lhs, rhs)
+        } else {
+            unreachable!()
+        };
+        match op {
+            Operator::Add => self.builder.build_float_add(lhs, rhs, "fadd").into(),
+            Operator::Sub => self.builder.build_float_sub(lhs, rhs, "fsub").into(),
+            Operator::Mult => self.builder.build_float_mul(lhs, rhs, "fmul").into(),
+            Operator::Div => self.builder.build_float_div(lhs, rhs, "fdiv").into(),
+            Operator::Mod => self.builder.build_float_rem(lhs, rhs, "fmod").into(),
+            Operator::FloorDiv => {
+                let div = self.builder.build_float_div(lhs, rhs, "fdiv");
+                let floor_intrinsic =
+                    self.module.get_function("llvm.floor.f64").unwrap_or_else(|| {
+                        let float = self.ctx.f64_type();
+                        let fn_type = float.fn_type(&[float.into()], false);
+                        self.module.add_function("llvm.floor.f64", fn_type, None)
+                    });
+                self.builder
+                    .build_call(floor_intrinsic, &[div.into()], "floor")
+                    .try_as_basic_value()
+                    .left()
+                    .unwrap()
+            }
+            // special implementation?
+            _ => unimplemented!(),
+        }
+    }
+
+    pub fn gen_expr(&mut self, expr: &Expr<Option<Type>>) -> BasicValueEnum<'ctx> {
+        let zero = self.ctx.i32_type().const_int(0, false);
+        match &expr.node {
+            ExprKind::Constant { value, .. } => {
+                let ty = expr.custom.unwrap();
+                self.gen_const(value, ty)
+            }
+            ExprKind::Name { id, .. } => {
+                let ptr = self.var_assignment.get(id).unwrap();
+                let primitives = &self.primitives;
+                // we should only dereference primitive types
+                if [primitives.int32, primitives.int64, primitives.float, primitives.bool]
+                    .contains(&self.unifier.get_representative(expr.custom.unwrap()))
+                {
+                    self.builder.build_load(*ptr, "load")
+                } else {
+                    (*ptr).into()
+                }
+            }
+            ExprKind::List { elts, .. } => {
+                // this shall be optimized later for constant primitive lists...
+                // we should use memcpy for that instead of generating thousands of stores
+                let elements = elts.iter().map(|x| self.gen_expr(x)).collect_vec();
+                let ty = if elements.is_empty() {
+                    self.ctx.i32_type().into()
+                } else {
+                    elements[0].get_type()
+                };
+                let arr_ptr = self.builder.build_array_alloca(
+                    ty,
+                    self.ctx.i32_type().const_int(elements.len() as u64, false),
+                    "tmparr",
+                );
+                let arr_ty = self.ctx.struct_type(
+                    &[self.ctx.i32_type().into(), ty.ptr_type(AddressSpace::Generic).into()],
+                    false,
+                );
+                let arr_str_ptr = self.builder.build_alloca(arr_ty, "tmparrstr");
+                unsafe {
+                    self.builder.build_store(
+                        arr_str_ptr.const_in_bounds_gep(&[zero, zero]),
+                        self.ctx.i32_type().const_int(elements.len() as u64, false),
+                    );
+                    self.builder.build_store(
+                        arr_str_ptr
+                            .const_in_bounds_gep(&[zero, self.ctx.i32_type().const_int(1, false)]),
+                        arr_ptr,
+                    );
+                    let arr_offset = self.ctx.i32_type().const_int(1, false);
+                    for (i, v) in elements.iter().enumerate() {
+                        let ptr = self.builder.build_in_bounds_gep(
+                            arr_ptr,
+                            &[zero, arr_offset, self.ctx.i32_type().const_int(i as u64, false)],
+                            "arr_element",
+                        );
+                        self.builder.build_store(ptr, *v);
+                    }
+                }
+                arr_str_ptr.into()
+            }
+            ExprKind::Tuple { elts, .. } => {
+                let element_val = elts.iter().map(|x| self.gen_expr(x)).collect_vec();
+                let element_ty = element_val.iter().map(BasicValueEnum::get_type).collect_vec();
+                let tuple_ty = self.ctx.struct_type(&element_ty, false);
+                let tuple_ptr = self.builder.build_alloca(tuple_ty, "tuple");
+                for (i, v) in element_val.into_iter().enumerate() {
+                    unsafe {
+                        let ptr = tuple_ptr.const_in_bounds_gep(&[
+                            zero,
+                            self.ctx.i32_type().const_int(i as u64, false),
+                        ]);
+                        self.builder.build_store(ptr, v);
+                    }
+                }
+                tuple_ptr.into()
+            }
+            ExprKind::Attribute { value, attr, .. } => {
+                // note that we would handle class methods directly in calls
+                let index = self.get_attr_index(value.custom.unwrap(), attr);
+                let val = self.gen_expr(value);
+                let ptr = if let BasicValueEnum::PointerValue(v) = val {
+                    v
+                } else {
+                    unreachable!();
+                };
+                unsafe {
+                    let ptr = ptr.const_in_bounds_gep(&[
+                        zero,
+                        self.ctx.i32_type().const_int(index as u64, false),
+                    ]);
+                    self.builder.build_load(ptr, "field")
+                }
+            }
+            ExprKind::BoolOp { op, values } => {
+                // requires conditional branches for short-circuiting...
+                let left = if let BasicValueEnum::IntValue(left) = self.gen_expr(&values[0]) {
+                    left
+                } else {
+                    unreachable!()
+                };
+                let current = self.builder.get_insert_block().unwrap().get_parent().unwrap();
+                let a_bb = self.ctx.append_basic_block(current, "a");
+                let b_bb = self.ctx.append_basic_block(current, "b");
+                let cont_bb = self.ctx.append_basic_block(current, "cont");
+                self.builder.build_conditional_branch(left, a_bb, b_bb);
+                let (a, b) = match op {
+                    Boolop::Or => {
+                        self.builder.position_at_end(a_bb);
+                        let a = self.ctx.bool_type().const_int(1, false);
+                        self.builder.build_unconditional_branch(cont_bb);
+                        self.builder.position_at_end(b_bb);
+                        let b = if let BasicValueEnum::IntValue(b) = self.gen_expr(&values[1]) {
+                            b
+                        } else {
+                            unreachable!()
+                        };
+                        self.builder.build_unconditional_branch(cont_bb);
+                        (a, b)
+                    }
+                    Boolop::And => {
+                        self.builder.position_at_end(a_bb);
+                        let a = if let BasicValueEnum::IntValue(a) = self.gen_expr(&values[1]) {
+                            a
+                        } else {
+                            unreachable!()
+                        };
+                        self.builder.build_unconditional_branch(cont_bb);
+                        self.builder.position_at_end(b_bb);
+                        let b = self.ctx.bool_type().const_int(0, false);
+                        self.builder.build_unconditional_branch(cont_bb);
+                        (a, b)
+                    }
+                };
+                self.builder.position_at_end(cont_bb);
+                let phi = self.builder.build_phi(self.ctx.bool_type(), "phi");
+                phi.add_incoming(&[(&a, a_bb), (&b, b_bb)]);
+                phi.as_basic_value()
+            }
+            ExprKind::BinOp { op, left, right } => {
+                let ty1 = self.unifier.get_representative(left.custom.unwrap());
+                let ty2 = self.unifier.get_representative(right.custom.unwrap());
+                let left = self.gen_expr(left);
+                let right = self.gen_expr(right);
+
+                // we can directly compare the types, because we've got their representatives
+                // which would be unchanged until further unification, which we would never do
+                // when doing code generation for function instances
+                if ty1 == ty2 && [self.primitives.int32, self.primitives.int64].contains(&ty1) {
+                    self.gen_int_ops(op, left, right)
+                } else if ty1 == ty2 && self.primitives.float == ty1 {
+                    self.gen_float_ops(op, left, right)
+                } else {
+                    unimplemented!()
+                }
+            }
+            ExprKind::UnaryOp { op, operand } => {
+                let ty = self.unifier.get_representative(operand.custom.unwrap());
+                let val = self.gen_expr(operand);
+                if ty == self.primitives.bool {
+                    let val =
+                        if let BasicValueEnum::IntValue(val) = val { val } else { unreachable!() };
+                    match op {
+                        ast::Unaryop::Invert | ast::Unaryop::Not => {
+                            self.builder.build_not(val, "not").into()
+                        }
+                        _ => val.into(),
+                    }
+                } else if [self.primitives.int32, self.primitives.int64].contains(&ty) {
+                    let val =
+                        if let BasicValueEnum::IntValue(val) = val { val } else { unreachable!() };
+                    match op {
+                        ast::Unaryop::USub => self.builder.build_int_neg(val, "neg").into(),
+                        ast::Unaryop::Invert => self.builder.build_not(val, "not").into(),
+                        ast::Unaryop::Not => self
+                            .builder
+                            .build_int_compare(
+                                inkwell::IntPredicate::EQ,
+                                val,
+                                val.get_type().const_zero(),
+                                "not",
+                            )
+                            .into(),
+                        _ => val.into(),
+                    }
+                } else if ty == self.primitives.float {
+                    let val = if let BasicValueEnum::FloatValue(val) = val {
+                        val
+                    } else {
+                        unreachable!()
+                    };
+                    match op {
+                        ast::Unaryop::USub => self.builder.build_float_neg(val, "neg").into(),
+                        ast::Unaryop::Not => self
+                            .builder
+                            .build_float_compare(
+                                inkwell::FloatPredicate::OEQ,
+                                val,
+                                val.get_type().const_zero(),
+                                "not",
+                            )
+                            .into(),
+                        _ => val.into(),
+                    }
+                } else {
+                    unimplemented!()
+                }
+            }
+            ExprKind::Compare { left, ops, comparators } => {
+                izip!(
+                    chain(once(left.as_ref()), comparators.iter()),
+                    comparators.iter(),
+                    ops.iter(),
+                )
+                .fold(None, |prev, (lhs, rhs, op)| {
+                    let ty = self.unifier.get_representative(lhs.custom.unwrap());
+                    let current =
+                        if [self.primitives.int32, self.primitives.int64, self.primitives.bool]
+                            .contains(&ty)
+                        {
+                            let (lhs, rhs) = if let (
+                                BasicValueEnum::IntValue(lhs),
+                                BasicValueEnum::IntValue(rhs),
+                            ) = (self.gen_expr(lhs), self.gen_expr(rhs))
+                            {
+                                (lhs, rhs)
+                            } else {
+                                unreachable!()
+                            };
+                            let op = match op {
+                                ast::Cmpop::Eq | ast::Cmpop::Is => inkwell::IntPredicate::EQ,
+                                ast::Cmpop::NotEq => inkwell::IntPredicate::NE,
+                                ast::Cmpop::Lt => inkwell::IntPredicate::SLT,
+                                ast::Cmpop::LtE => inkwell::IntPredicate::SLE,
+                                ast::Cmpop::Gt => inkwell::IntPredicate::SGT,
+                                ast::Cmpop::GtE => inkwell::IntPredicate::SGE,
+                                _ => unreachable!(),
+                            };
+                            self.builder.build_int_compare(op, lhs, rhs, "cmp")
+                        } else if ty == self.primitives.float {
+                            let (lhs, rhs) = if let (
+                                BasicValueEnum::FloatValue(lhs),
+                                BasicValueEnum::FloatValue(rhs),
+                            ) = (self.gen_expr(lhs), self.gen_expr(rhs))
+                            {
+                                (lhs, rhs)
+                            } else {
+                                unreachable!()
+                            };
+                            let op = match op {
+                                ast::Cmpop::Eq | ast::Cmpop::Is => inkwell::FloatPredicate::OEQ,
+                                ast::Cmpop::NotEq => inkwell::FloatPredicate::ONE,
+                                ast::Cmpop::Lt => inkwell::FloatPredicate::OLT,
+                                ast::Cmpop::LtE => inkwell::FloatPredicate::OLE,
+                                ast::Cmpop::Gt => inkwell::FloatPredicate::OGT,
+                                ast::Cmpop::GtE => inkwell::FloatPredicate::OGE,
+                                _ => unreachable!(),
+                            };
+                            self.builder.build_float_compare(op, lhs, rhs, "cmp")
+                        } else {
+                            unimplemented!()
+                        };
+                    prev.map(|v| self.builder.build_and(v, current, "cmp")).or(Some(current))
+                })
+                .unwrap()
+                .into() // as there should be at least 1 element, it should never be none
+            }
+            ExprKind::IfExp { test, body, orelse } => {
+                let test = if let BasicValueEnum::IntValue(test) = self.gen_expr(test) {
+                    test
+                } else {
+                    unreachable!()
+                };
+
+                let current = self.builder.get_insert_block().unwrap().get_parent().unwrap();
+                let then_bb = self.ctx.append_basic_block(current, "then");
+                let else_bb = self.ctx.append_basic_block(current, "else");
+                let cont_bb = self.ctx.append_basic_block(current, "cont");
+                self.builder.build_conditional_branch(test, then_bb, else_bb);
+                self.builder.position_at_end(then_bb);
+                let a = self.gen_expr(body);
+                self.builder.build_unconditional_branch(cont_bb);
+                self.builder.position_at_end(else_bb);
+                let b = self.gen_expr(orelse);
+                self.builder.build_unconditional_branch(cont_bb);
+                self.builder.position_at_end(cont_bb);
+                let phi = self.builder.build_phi(a.get_type(), "ifexpr");
+                phi.add_incoming(&[(&a, then_bb), (&b, else_bb)]);
+                phi.as_basic_value()
+            }
+            _ => unimplemented!(),
+        }
+    }
+}

nac3core/src/codegen/mod.rs

@@ -0,0 +1,343 @@
+use crate::{
+    symbol_resolver::SymbolResolver,
+    top_level::{TopLevelContext, TopLevelDef},
+    typecheck::{
+        type_inferencer::PrimitiveStore,
+        typedef::{FunSignature, Type, TypeEnum, Unifier},
+    },
+};
+use crossbeam::channel::{unbounded, Receiver, Sender};
+use inkwell::{
+    basic_block::BasicBlock,
+    builder::Builder,
+    context::Context,
+    module::Module,
+    types::{BasicType, BasicTypeEnum},
+    values::PointerValue,
+    AddressSpace,
+};
+use itertools::Itertools;
+use parking_lot::{Condvar, Mutex};
+use rustpython_parser::ast::Stmt;
+use std::collections::HashMap;
+use std::sync::{
+    atomic::{AtomicBool, Ordering},
+    Arc,
+};
+use std::thread;
+
+mod expr;
+mod stmt;
+
+#[cfg(test)]
+mod test;
+
+pub struct CodeGenContext<'ctx, 'a> {
+    pub ctx: &'ctx Context,
+    pub builder: Builder<'ctx>,
+    pub module: Module<'ctx>,
+    pub top_level: &'a TopLevelContext,
+    pub unifier: Unifier,
+    pub resolver: Arc<dyn SymbolResolver>,
+    pub var_assignment: HashMap<String, PointerValue<'ctx>>,
+    pub type_cache: HashMap<Type, BasicTypeEnum<'ctx>>,
+    pub primitives: PrimitiveStore,
+    // stores the alloca for variables
+    pub init_bb: BasicBlock<'ctx>,
+    // where continue and break should go to respectively
+    // the first one is the test_bb, and the second one is bb after the loop
+    pub loop_bb: Option<(BasicBlock<'ctx>, BasicBlock<'ctx>)>,
+}
+
+type Fp = Box<dyn Fn(&Module) + Send + Sync>;
+
+pub struct WithCall {
+    fp: Fp,
+}
+
+impl WithCall {
+    pub fn new(fp: Fp) -> WithCall {
+        WithCall { fp }
+    }
+
+    pub fn run<'ctx>(&self, m: &Module<'ctx>) {
+        (self.fp)(m)
+    }
+}
+
+pub struct WorkerRegistry {
+    sender: Arc<Sender<Option<CodeGenTask>>>,
+    receiver: Arc<Receiver<Option<CodeGenTask>>>,
+    panicked: AtomicBool,
+    task_count: Mutex<usize>,
+    thread_count: usize,
+    wait_condvar: Condvar,
+}
+
+impl WorkerRegistry {
+    pub fn create_workers(
+        names: &[&str],
+        top_level_ctx: Arc<TopLevelContext>,
+        f: Arc<WithCall>,
+    ) -> (Arc<WorkerRegistry>, Vec<thread::JoinHandle<()>>) {
+        let (sender, receiver) = unbounded();
+        let task_count = Mutex::new(0);
+        let wait_condvar = Condvar::new();
+
+        let registry = Arc::new(WorkerRegistry {
+            sender: Arc::new(sender),
+            receiver: Arc::new(receiver),
+            thread_count: names.len(),
+            panicked: AtomicBool::new(false),
+            task_count,
+            wait_condvar,
+        });
+
+        let mut handles = Vec::new();
+        for name in names.iter() {
+            let top_level_ctx = top_level_ctx.clone();
+            let registry = registry.clone();
+            let registry2 = registry.clone();
+            let name = name.to_string();
+            let f = f.clone();
+            let handle = thread::spawn(move || {
+                registry.worker_thread(name, top_level_ctx, f);
+            });
+            let handle = thread::spawn(move || {
+                if let Err(e) = handle.join() {
+                    if let Some(e) = e.downcast_ref::<&'static str>() {
+                        eprintln!("Got an error: {}", e);
+                    } else {
+                        eprintln!("Got an unknown error: {:?}", e);
+                    }
+                    registry2.panicked.store(true, Ordering::SeqCst);
+                    registry2.wait_condvar.notify_all();
+                }
+            });
+            handles.push(handle);
+        }
+        (registry, handles)
+    }
+
+    pub fn wait_tasks_complete(&self, handles: Vec<thread::JoinHandle<()>>) {
+        {
+            let mut count = self.task_count.lock();
+            while *count != 0 {
+                if self.panicked.load(Ordering::SeqCst) {
+                    break;
+                }
+                self.wait_condvar.wait(&mut count);
+            }
+        }
+        for _ in 0..self.thread_count {
+            self.sender.send(None).unwrap();
+        }
+        {
+            let mut count = self.task_count.lock();
+            while *count != self.thread_count {
+                if self.panicked.load(Ordering::SeqCst) {
+                    break;
+                }
+                self.wait_condvar.wait(&mut count);
+            }
+        }
+        for handle in handles {
+            handle.join().unwrap();
+        }
+        if self.panicked.load(Ordering::SeqCst) {
+            panic!("tasks panicked");
+        }
+    }
+
+    pub fn add_task(&self, task: CodeGenTask) {
+        *self.task_count.lock() += 1;
+        self.sender.send(Some(task)).unwrap();
+    }
+
+    fn worker_thread(
+        &self,
+        module_name: String,
+        top_level_ctx: Arc<TopLevelContext>,
+        f: Arc<WithCall>,
+    ) {
+        let context = Context::create();
+        let mut builder = context.create_builder();
+        let mut module = context.create_module(&module_name);
+
+        while let Some(task) = self.receiver.recv().unwrap() {
+            let result = gen_func(&context, builder, module, task, top_level_ctx.clone());
+            builder = result.0;
+            module = result.1;
+            *self.task_count.lock() -= 1;
+            self.wait_condvar.notify_all();
+        }
+
+        // do whatever...
+        let mut lock = self.task_count.lock();
+        module.verify().unwrap();
+        f.run(&module);
+        *lock += 1;
+        self.wait_condvar.notify_all();
+    }
+}
+
+pub struct CodeGenTask {
+    pub subst: Vec<(Type, Type)>,
+    pub symbol_name: String,
+    pub signature: FunSignature,
+    pub body: Vec<Stmt<Option<Type>>>,
+    pub unifier_index: usize,
+    pub resolver: Arc<dyn SymbolResolver + Send + Sync>,
+}
+
+fn get_llvm_type<'ctx>(
+    ctx: &'ctx Context,
+    unifier: &mut Unifier,
+    top_level: &TopLevelContext,
+    type_cache: &mut HashMap<Type, BasicTypeEnum<'ctx>>,
+    ty: Type,
+) -> BasicTypeEnum<'ctx> {
+    use TypeEnum::*;
+    // we assume the type cache should already contain primitive types,
+    // and they should be passed by value instead of passing as pointer.
+    type_cache.get(&unifier.get_representative(ty)).cloned().unwrap_or_else(|| {
+        match &*unifier.get_ty(ty) {
+            TObj { obj_id, fields, .. } => {
+                // a struct with fields in the order of declaration
+                let defs = top_level.definitions.read();
+                let definition = defs.get(obj_id.0).unwrap();
+                let ty = if let TopLevelDef::Class { fields: fields_list, .. } = &*definition.read()
+                {
+                    let fields = fields.borrow();
+                    let fields = fields_list
+                        .iter()
+                        .map(|f| get_llvm_type(ctx, unifier, top_level, type_cache, fields[&f.0]))
+                        .collect_vec();
+                    ctx.struct_type(&fields, false).ptr_type(AddressSpace::Generic).into()
+                } else {
+                    unreachable!()
+                };
+                ty
+            }
+            TTuple { ty } => {
+                // a struct with fields in the order present in the tuple
+                let fields = ty
+                    .iter()
+                    .map(|ty| get_llvm_type(ctx, unifier, top_level, type_cache, *ty))
+                    .collect_vec();
+                ctx.struct_type(&fields, false).ptr_type(AddressSpace::Generic).into()
+            }
+            TList { ty } => {
+                // a struct with an integer and a pointer to an array
+                let element_type = get_llvm_type(ctx, unifier, top_level, type_cache, *ty);
+                let fields =
+                    [ctx.i32_type().into(), element_type.ptr_type(AddressSpace::Generic).into()];
+                ctx.struct_type(&fields, false).ptr_type(AddressSpace::Generic).into()
+            }
+            TVirtual { .. } => unimplemented!(),
+            _ => unreachable!(),
+        }
+    })
+}
+
+pub fn gen_func<'ctx>(
+    context: &'ctx Context,
+    builder: Builder<'ctx>,
+    module: Module<'ctx>,
+    task: CodeGenTask,
+    top_level_ctx: Arc<TopLevelContext>,
+) -> (Builder<'ctx>, Module<'ctx>) {
+    // unwrap_or(0) is for unit tests without using rayon
+    let (mut unifier, primitives) = {
+        let unifiers = top_level_ctx.unifiers.read();
+        let (unifier, primitives) = &unifiers[task.unifier_index];
+        (Unifier::from_shared_unifier(unifier), *primitives)
+    };
+
+    for (a, b) in task.subst.iter() {
+        // this should be unification between variables and concrete types
+        // and should not cause any problem...
+        unifier.unify(*a, *b).unwrap();
+    }
+
+    // rebuild primitive store with unique representatives
+    let primitives = PrimitiveStore {
+        int32: unifier.get_representative(primitives.int32),
+        int64: unifier.get_representative(primitives.int64),
+        float: unifier.get_representative(primitives.float),
+        bool: unifier.get_representative(primitives.bool),
+        none: unifier.get_representative(primitives.none),
+    };
+
+    let mut type_cache: HashMap<_, _> = [
+        (unifier.get_representative(primitives.int32), context.i32_type().into()),
+        (unifier.get_representative(primitives.int64), context.i64_type().into()),
+        (unifier.get_representative(primitives.float), context.f64_type().into()),
+        (unifier.get_representative(primitives.bool), context.bool_type().into()),
+    ]
+    .iter()
+    .cloned()
+    .collect();
+
+    let params = task
+        .signature
+        .args
+        .iter()
+        .map(|arg| {
+            get_llvm_type(&context, &mut unifier, top_level_ctx.as_ref(), &mut type_cache, arg.ty)
+        })
+        .collect_vec();
+
+    let fn_type = if unifier.unioned(task.signature.ret, primitives.none) {
+        context.void_type().fn_type(&params, false)
+    } else {
+        get_llvm_type(
+            &context,
+            &mut unifier,
+            top_level_ctx.as_ref(),
+            &mut type_cache,
+            task.signature.ret,
+        )
+        .fn_type(&params, false)
+    };
+
+    let fn_val = module.add_function(&task.symbol_name, fn_type, None);
+    let init_bb = context.append_basic_block(fn_val, "init");
+    builder.position_at_end(init_bb);
+    let body_bb = context.append_basic_block(fn_val, "body");
+
+    let mut var_assignment = HashMap::new();
+    for (n, arg) in task.signature.args.iter().enumerate() {
+        let param = fn_val.get_nth_param(n as u32).unwrap();
+        let alloca = builder.build_alloca(
+            get_llvm_type(&context, &mut unifier, top_level_ctx.as_ref(), &mut type_cache, arg.ty),
+            &arg.name,
+        );
+        builder.build_store(alloca, param);
+        var_assignment.insert(arg.name.clone(), alloca);
+    }
+    builder.build_unconditional_branch(body_bb);
+    builder.position_at_end(body_bb);
+
+    let mut code_gen_context = CodeGenContext {
+        ctx: &context,
+        resolver: task.resolver,
+        top_level: top_level_ctx.as_ref(),
+        loop_bb: None,
+        var_assignment,
+        type_cache,
+        primitives,
+        init_bb,
+        builder,
+        module,
+        unifier,
+    };
+
+    for stmt in task.body.iter() {
+        code_gen_context.gen_stmt(stmt);
+    }
+
+    let CodeGenContext { builder, module, .. } = code_gen_context;
+
+    (builder, module)
+}

nac3core/src/codegen/stmt.rs

@@ -0,0 +1,138 @@
+use super::CodeGenContext;
+use crate::typecheck::typedef::Type;
+use inkwell::values::{BasicValue, BasicValueEnum, PointerValue};
+use rustpython_parser::ast::{Expr, ExprKind, Stmt, StmtKind};
+
+impl<'ctx, 'a> CodeGenContext<'ctx, 'a> {
+    fn gen_var(&mut self, ty: Type) -> PointerValue<'ctx> {
+        // put the alloca in init block
+        let current = self.builder.get_insert_block().unwrap();
+        // position before the last branching instruction...
+        self.builder.position_before(&self.init_bb.get_last_instruction().unwrap());
+        let ty = self.get_llvm_type(ty);
+        let ptr = self.builder.build_alloca(ty, "tmp");
+        self.builder.position_at_end(current);
+        ptr
+    }
+
+    fn parse_pattern(&mut self, pattern: &Expr<Option<Type>>) -> PointerValue<'ctx> {
+        // very similar to gen_expr, but we don't do an extra load at the end
+        // and we flatten nested tuples
+        match &pattern.node {
+            ExprKind::Name { id, .. } => {
+                self.var_assignment.get(id).cloned().unwrap_or_else(|| {
+                    let ptr = self.gen_var(pattern.custom.unwrap());
+                    self.var_assignment.insert(id.clone(), ptr);
+                    ptr
+                })
+            }
+            ExprKind::Attribute { value, attr, .. } => {
+                let index = self.get_attr_index(value.custom.unwrap(), attr);
+                let val = self.gen_expr(value);
+                let ptr = if let BasicValueEnum::PointerValue(v) = val {
+                    v
+                } else {
+                    unreachable!();
+                };
+                unsafe {
+                    ptr.const_in_bounds_gep(&[
+                        self.ctx.i32_type().const_zero(),
+                        self.ctx.i32_type().const_int(index as u64, false),
+                    ])
+                }
+            }
+            ExprKind::Subscript { .. } => unimplemented!(),
+            _ => unreachable!(),
+        }
+    }
+
+    fn gen_assignment(&mut self, target: &Expr<Option<Type>>, value: BasicValueEnum<'ctx>) {
+        if let ExprKind::Tuple { elts, .. } = &target.node {
+            if let BasicValueEnum::PointerValue(ptr) = value {
+                for (i, elt) in elts.iter().enumerate() {
+                    unsafe {
+                        let t = ptr.const_in_bounds_gep(&[
+                            self.ctx.i32_type().const_zero(),
+                            self.ctx.i32_type().const_int(i as u64, false),
+                        ]);
+                        let v = self.builder.build_load(t, "tmpload");
+                        self.gen_assignment(elt, v);
+                    }
+                }
+            } else {
+                unreachable!()
+            }
+        } else {
+            let ptr = self.parse_pattern(target);
+            self.builder.build_store(ptr, value);
+        }
+    }
+
+    pub fn gen_stmt(&mut self, stmt: &Stmt<Option<Type>>) {
+        match &stmt.node {
+            StmtKind::Expr { value } => {
+                self.gen_expr(&value);
+            }
+            StmtKind::Return { value } => {
+                let value = value.as_ref().map(|v| self.gen_expr(&v));
+                let value = value.as_ref().map(|v| v as &dyn BasicValue);
+                self.builder.build_return(value);
+            }
+            StmtKind::AnnAssign { target, value, .. } => {
+                if let Some(value) = value {
+                    let value = self.gen_expr(&value);
+                    self.gen_assignment(target, value);
+                }
+            }
+            StmtKind::Assign { targets, value, .. } => {
+                let value = self.gen_expr(&value);
+                for target in targets.iter() {
+                    self.gen_assignment(target, value);
+                }
+            }
+            StmtKind::Continue => {
+                self.builder.build_unconditional_branch(self.loop_bb.unwrap().0);
+            }
+            StmtKind::Break => {
+                self.builder.build_unconditional_branch(self.loop_bb.unwrap().1);
+            }
+            StmtKind::While { test, body, orelse } => {
+                let current = self.builder.get_insert_block().unwrap().get_parent().unwrap();
+                let test_bb = self.ctx.append_basic_block(current, "test");
+                let body_bb = self.ctx.append_basic_block(current, "body");
+                let cont_bb = self.ctx.append_basic_block(current, "cont");
+                // if there is no orelse, we just go to cont_bb
+                let orelse_bb = if orelse.is_empty() {
+                    cont_bb
+                } else {
+                    self.ctx.append_basic_block(current, "orelse")
+                };
+                // store loop bb information and restore it later
+                let loop_bb = self.loop_bb.replace((test_bb, cont_bb));
+                self.builder.build_unconditional_branch(test_bb);
+                self.builder.position_at_end(test_bb);
+                let test = self.gen_expr(test);
+                if let BasicValueEnum::IntValue(test) = test {
+                    self.builder.build_conditional_branch(test, body_bb, orelse_bb);
+                } else {
+                    unreachable!()
+                };
+                self.builder.position_at_end(body_bb);
+                for stmt in body.iter() {
+                    self.gen_stmt(stmt);
+                }
+                self.builder.build_unconditional_branch(test_bb);
+                if !orelse.is_empty() {
+                    self.builder.position_at_end(orelse_bb);
+                    for stmt in orelse.iter() {
+                        self.gen_stmt(stmt);
+                    }
+                    self.builder.build_unconditional_branch(cont_bb);
+                }
+                self.builder.position_at_end(cont_bb);
+                self.loop_bb = loop_bb;
+            }
+            _ => unimplemented!(),
+        }
+    }
+}

nac3core/src/codegen/test.rs

@@ -0,0 +1,247 @@
+use super::{CodeGenTask, WorkerRegistry};
+use crate::{
+    codegen::WithCall,
+    location::Location,
+    symbol_resolver::{SymbolResolver, SymbolValue},
+    top_level::{DefinitionId, TopLevelContext},
+    typecheck::{
+        magic_methods::set_primitives_magic_methods,
+        type_inferencer::{CodeLocation, FunctionData, Inferencer, PrimitiveStore},
+        typedef::{CallId, FunSignature, FuncArg, Type, TypeEnum, Unifier},
+    },
+};
+use indoc::indoc;
+use parking_lot::RwLock;
+use rustpython_parser::{ast::fold::Fold, parser::parse_program};
+use std::collections::HashMap;
+use std::sync::Arc;
+
+#[derive(Clone)]
+struct Resolver {
+    id_to_type: HashMap<String, Type>,
+    id_to_def: HashMap<String, DefinitionId>,
+    class_names: HashMap<String, Type>,
+}
+
+impl SymbolResolver for Resolver {
+    fn get_symbol_type(&self, _: &mut Unifier, _: &PrimitiveStore, str: &str) -> Option<Type> {
+        self.id_to_type.get(str).cloned()
+    }
+
+    fn get_symbol_value(&self, _: &str) -> Option<SymbolValue> {
+        unimplemented!()
+    }
+
+    fn get_symbol_location(&self, _: &str) -> Option<Location> {
+        unimplemented!()
+    }
+
+    fn get_identifier_def(&self, id: &str) -> Option<DefinitionId> {
+        self.id_to_def.get(id).cloned()
+    }
+}
+
+struct TestEnvironment {
+    pub unifier: Unifier,
+    pub function_data: FunctionData,
+    pub primitives: PrimitiveStore,
+    pub id_to_name: HashMap<usize, String>,
+    pub identifier_mapping: HashMap<String, Type>,
+    pub virtual_checks: Vec<(Type, Type)>,
+    pub calls: HashMap<CodeLocation, CallId>,
+    pub top_level: TopLevelContext,
+}
+
+impl TestEnvironment {
+    pub fn basic_test_env() -> TestEnvironment {
+        let mut unifier = Unifier::new();
+
+        let int32 = unifier.add_ty(TypeEnum::TObj {
+            obj_id: DefinitionId(0),
+            fields: HashMap::new().into(),
+            params: HashMap::new().into(),
+        });
+        let int64 = unifier.add_ty(TypeEnum::TObj {
+            obj_id: DefinitionId(1),
+            fields: HashMap::new().into(),
+            params: HashMap::new().into(),
+        });
+        let float = unifier.add_ty(TypeEnum::TObj {
+            obj_id: DefinitionId(2),
+            fields: HashMap::new().into(),
+            params: HashMap::new().into(),
+        });
+        let bool = unifier.add_ty(TypeEnum::TObj {
+            obj_id: DefinitionId(3),
+            fields: HashMap::new().into(),
+            params: HashMap::new().into(),
+        });
+        let none = unifier.add_ty(TypeEnum::TObj {
+            obj_id: DefinitionId(4),
+            fields: HashMap::new().into(),
+            params: HashMap::new().into(),
+        });
+        let primitives = PrimitiveStore { int32, int64, float, bool, none };
+        set_primitives_magic_methods(&primitives, &mut unifier);
+
+        let id_to_name = [
+            (0, "int32".to_string()),
+            (1, "int64".to_string()),
+            (2, "float".to_string()),
+            (3, "bool".to_string()),
+            (4, "none".to_string()),
+        ]
+        .iter()
+        .cloned()
+        .collect();
+
+        let mut identifier_mapping = HashMap::new();
+        identifier_mapping.insert("None".into(), none);
+
+        let resolver = Arc::new(Resolver {
+            id_to_type: identifier_mapping.clone(),
+            id_to_def: Default::default(),
+            class_names: Default::default(),
+        }) as Arc<dyn SymbolResolver + Send + Sync>;
+
+        TestEnvironment {
+            unifier,
+            top_level: TopLevelContext {
+                definitions: Default::default(),
+                unifiers: Default::default(),
+                // conetexts: Default::default(),
+            },
+            function_data: FunctionData {
+                resolver,
+                bound_variables: Vec::new(),
+                return_type: Some(primitives.int32),
+            },
+            primitives,
+            id_to_name,
+            identifier_mapping,
+            virtual_checks: Vec::new(),
+            calls: HashMap::new(),
+        }
+    }
+
+    fn get_inferencer(&mut self) -> Inferencer {
+        Inferencer {
+            top_level: &self.top_level,
+            function_data: &mut self.function_data,
+            unifier: &mut self.unifier,
+            variable_mapping: Default::default(),
+            primitives: &mut self.primitives,
+            virtual_checks: &mut self.virtual_checks,
+            calls: &mut self.calls,
+        }
+    }
+}
+
+#[test]
+fn test_primitives() {
+    let mut env = TestEnvironment::basic_test_env();
+    let threads = ["test"];
+    let signature = FunSignature {
+        args: vec![
+            FuncArg { name: "a".to_string(), ty: env.primitives.int32, default_value: None },
+            FuncArg { name: "b".to_string(), ty: env.primitives.int32, default_value: None },
+        ],
+        ret: env.primitives.int32,
+        vars: HashMap::new(),
+    };
+
+    let mut inferencer = env.get_inferencer();
+    inferencer.variable_mapping.insert("a".into(), inferencer.primitives.int32);
+    inferencer.variable_mapping.insert("b".into(), inferencer.primitives.int32);
+    let source = indoc! { "
+        c = a + b
+        d = a if c == 1 else 0
+        return d
+        "};
+    let statements = parse_program(source).unwrap();
+
+    let statements = statements
+        .into_iter()
+        .map(|v| inferencer.fold_stmt(v))
+        .collect::<Result<Vec<_>, _>>()
+        .unwrap();
+    let mut identifiers = vec!["a".to_string(), "b".to_string()];
+    inferencer.check_block(&statements, &mut identifiers).unwrap();
+
+    let top_level = Arc::new(TopLevelContext {
+        definitions: Default::default(),
+        unifiers: Arc::new(RwLock::new(vec![(env.unifier.get_shared_unifier(), env.primitives)])),
+        // conetexts: Default::default(),
+    });
+    let task = CodeGenTask {
+        subst: Default::default(),
+        symbol_name: "testing".to_string(),
+        body: statements,
+        unifier_index: 0,
+        resolver: env.function_data.resolver.clone(),
+        signature,
+    };
+
+    let f = Arc::new(WithCall::new(Box::new(|module| {
+        // the following IR is equivalent to
+        // ```
+        // ; ModuleID = 'test.ll'
+        // source_filename = "test"
+        //
+        // ; Function Attrs: norecurse nounwind readnone
+        // define i32 @testing(i32 %0, i32 %1) local_unnamed_addr #0 {
+        // init:
+        //   %add = add i32 %1, %0
+        //   %cmp = icmp eq i32 %add, 1
+        //   %ifexpr = select i1 %cmp, i32 %0, i32 0
+        //   ret i32 %ifexpr
+        // }
+        //
+        // attributes #0 = { norecurse nounwind readnone }
+        // ```
+        // after O2 optimization
+
+        let expected = indoc! {"
+            ; ModuleID = 'test'
+            source_filename = \"test\"
+
+            define i32 @testing(i32 %0, i32 %1) {
+            init:
+              %a = alloca i32, align 4
+              store i32 %0, i32* %a, align 4
+              %b = alloca i32, align 4
+              store i32 %1, i32* %b, align 4
+              %tmp = alloca i32, align 4
+              %tmp4 = alloca i32, align 4
+              br label %body
+
+            body:                                             ; preds = %init
+              %load = load i32, i32* %a, align 4
+              %load1 = load i32, i32* %b, align 4
+              %add = add i32 %load, %load1
+              store i32 %add, i32* %tmp, align 4
+              %load2 = load i32, i32* %tmp, align 4
+              %cmp = icmp eq i32 %load2, 1
+              br i1 %cmp, label %then, label %else
+
+            then:                                             ; preds = %body
+              %load3 = load i32, i32* %a, align 4
+              br label %cont
+
+            else:                                             ; preds = %body
+              br label %cont
+
+            cont:                                             ; preds = %else, %then
+              %ifexpr = phi i32 [ %load3, %then ], [ 0, %else ]
+              store i32 %ifexpr, i32* %tmp4, align 4
+              %load5 = load i32, i32* %tmp4, align 4
+              ret i32 %load5
+            }
+       "}
+        .trim();
+        assert_eq!(expected, module.print_to_string().to_str().unwrap().trim());
+    })));
+    let (registry, handles) = WorkerRegistry::create_workers(&threads, top_level, f);
+    registry.add_task(task);
+    registry.wait_tasks_complete(handles);
+}

nac3core/src/context/inference_context.rs

@@ -1,212 +0,0 @@
-use super::TopLevelContext;
-use crate::typedef::*;
-use std::boxed::Box;
-use std::collections::HashMap;
-
-struct ContextStack<'a> {
-    /// stack level, starts from 0
-    level: u32,
-    /// stack of variable definitions containing (id, def, level) where `def` is the original
-    /// definition in `level-1`.
-    var_defs: Vec<(usize, VarDef<'a>, u32)>,
-    /// stack of symbol definitions containing (name, level) where `level` is the smallest level
-    /// where the name is assigned a value
-    sym_def: Vec<(&'a str, u32)>,
-}
-
-pub struct InferenceContext<'a> {
-    /// top level context
-    top_level: TopLevelContext<'a>,
-
-    /// list of primitive instances
-    primitives: Vec<Type>,
-    /// list of variable instances
-    variables: Vec<Type>,
-    /// identifier to (type, readable) mapping.
-    /// an identifier might be defined earlier but has no value (for some code path), thus not
-    /// readable.
-    sym_table: HashMap<&'a str, (Type, bool)>,
-    /// resolution function reference, that may resolve unbounded identifiers to some type
-    resolution_fn: Box<dyn FnMut(&str) -> Result<Type, String>>,
-    /// stack
-    stack: ContextStack<'a>,
-}
-
-// non-trivial implementations here
-impl<'a> InferenceContext<'a> {
-    /// return a new `InferenceContext` from `TopLevelContext` and resolution function.
-    pub fn new(
-        top_level: TopLevelContext,
-        resolution_fn: Box<dyn FnMut(&str) -> Result<Type, String>>,
-    ) -> InferenceContext {
-        let primitives = (0..top_level.primitive_defs.len())
-            .map(|v| TypeEnum::PrimitiveType(PrimitiveId(v)).into())
-            .collect();
-        let variables = (0..top_level.var_defs.len())
-            .map(|v| TypeEnum::TypeVariable(VariableId(v)).into())
-            .collect();
-        InferenceContext {
-            top_level,
-            primitives,
-            variables,
-            sym_table: HashMap::new(),
-            resolution_fn,
-            stack: ContextStack {
-                level: 0,
-                var_defs: Vec::new(),
-                sym_def: Vec::new(),
-            },
-        }
-    }
-
-    /// execute the function with new scope.
-    /// variable assignment would be limited within the scope (not readable outside), and type
-    /// variable type guard would be limited within the scope.
-    /// returns the list of variables assigned within the scope, and the result of the function
-    pub fn with_scope<F, R>(&mut self, f: F) -> (Vec<&'a str>, R)
-    where
-        F: FnOnce(&mut Self) -> R,
-    {
-        self.stack.level += 1;
-        let result = f(self);
-        self.stack.level -= 1;
-        while !self.stack.var_defs.is_empty() {
-            let (_, _, level) = self.stack.var_defs.last().unwrap();
-            if *level > self.stack.level {
-                let (id, def, _) = self.stack.var_defs.pop().unwrap();
-                self.top_level.var_defs[id] = def;
-            } else {
-                break;
-            }
-        }
-        let mut poped_names = Vec::new();
-        while !self.stack.sym_def.is_empty() {
-            let (_, level) = self.stack.sym_def.last().unwrap();
-            if *level > self.stack.level {
-                let (name, _) = self.stack.sym_def.pop().unwrap();
-                self.sym_table.remove(name).unwrap();
-                poped_names.push(name);
-            } else {
-                break;
-            }
-        }
-        (poped_names, result)
-    }
-
-    /// assign a type to an identifier.
-    /// may return error if the identifier was defined but with different type
-    pub fn assign(&mut self, name: &'a str, ty: Type) -> Result<Type, String> {
-        if let Some((t, x)) = self.sym_table.get_mut(name) {
-            if t == &ty {
-                if !*x {
-                    self.stack.sym_def.push((name, self.stack.level));
-                }
-                *x = true;
-                Ok(ty)
-            } else {
-                Err("different types".into())
-            }
-        } else {
-            self.stack.sym_def.push((name, self.stack.level));
-            self.sym_table.insert(name, (ty.clone(), true));
-            Ok(ty)
-        }
-    }
-
-    /// check if an identifier is already defined
-    pub fn defined(&self, name: &str) -> bool {
-        self.sym_table.get(name).is_some()
-    }
-
-    /// get the type of an identifier
-    /// may return error if the identifier is not defined, and cannot be resolved with the
-    /// resolution function.
-    pub fn resolve(&mut self, name: &str) -> Result<Type, String> {
-        if let Some((t, x)) = self.sym_table.get(name) {
-            if *x {
-                Ok(t.clone())
-            } else {
-                Err("may not have value".into())
-            }
-        } else {
-            self.resolution_fn.as_mut()(name)
-        }
-    }
-
-    /// restrict the bound of a type variable by replacing its definition.
-    /// used for implementing type guard
-    pub fn restrict(&mut self, id: VariableId, mut def: VarDef<'a>) {
-        std::mem::swap(self.top_level.var_defs.get_mut(id.0).unwrap(), &mut def);
-        self.stack.var_defs.push((id.0, def, self.stack.level));
-    }
-}
-
-// trivial getters:
-impl<'a> InferenceContext<'a> {
-    pub fn get_primitive(&self, id: PrimitiveId) -> Type {
-        self.primitives.get(id.0).unwrap().clone()
-    }
-    pub fn get_variable(&self, id: VariableId) -> Type {
-        self.variables.get(id.0).unwrap().clone()
-    }
-
-    pub fn get_fn_def(&self, name: &str) -> Option<&FnDef> {
-        self.top_level.fn_table.get(name)
-    }
-    pub fn get_primitive_def(&self, id: PrimitiveId) -> &TypeDef {
-        self.top_level.primitive_defs.get(id.0).unwrap()
-    }
-    pub fn get_class_def(&self, id: ClassId) -> &ClassDef {
-        self.top_level.class_defs.get(id.0).unwrap()
-    }
-    pub fn get_parametric_def(&self, id: ParamId) -> &ParametricDef {
-        self.top_level.parametric_defs.get(id.0).unwrap()
-    }
-    pub fn get_variable_def(&self, id: VariableId) -> &VarDef {
-        self.top_level.var_defs.get(id.0).unwrap()
-    }
-    pub fn get_type(&self, name: &str) -> Option<Type> {
-        self.top_level.get_type(name)
-    }
-}
-
-impl TypeEnum {
-    pub fn subst(&self, map: &HashMap<VariableId, Type>) -> TypeEnum {
-        match self {
-            TypeEnum::TypeVariable(id) => map.get(id).map(|v| v.as_ref()).unwrap_or(self).clone(),
-            TypeEnum::ParametricType(id, params) => TypeEnum::ParametricType(
-                *id,
-                params
-                    .iter()
-                    .map(|v| v.as_ref().subst(map).into())
-                    .collect(),
-            ),
-            _ => self.clone(),
-        }
-    }
-
-    pub fn get_subst(&self, ctx: &InferenceContext) -> HashMap<VariableId, Type> {
-        match self {
-            TypeEnum::ParametricType(id, params) => {
-                let vars = &ctx.get_parametric_def(*id).params;
-                vars.iter()
-                    .zip(params)
-                    .map(|(v, p)| (*v, p.as_ref().clone().into()))
-                    .collect()
-            }
-            // if this proves to be slow, we can use option type
-            _ => HashMap::new(),
-        }
-    }
-
-    pub fn get_base<'b: 'a, 'a>(&'a self, ctx: &'b InferenceContext) -> Option<&'b TypeDef> {
-        match self {
-            TypeEnum::PrimitiveType(id) => Some(ctx.get_primitive_def(*id)),
-            TypeEnum::ClassType(id) | TypeEnum::VirtualClassType(id) => {
-                Some(&ctx.get_class_def(*id).base)
-            }
-            TypeEnum::ParametricType(id, _) => Some(&ctx.get_parametric_def(*id).base),
-            _ => None,
-        }
-    }
-}

nac3core/src/context/mod.rs

@@ -1,4 +0,0 @@
-mod inference_context;
-mod top_level_context;
-pub use inference_context::InferenceContext;
-pub use top_level_context::TopLevelContext;

nac3core/src/context/top_level_context.rs

@@ -1,136 +0,0 @@
-use crate::typedef::*;
-use std::collections::HashMap;
-use std::rc::Rc;
-
-/// Structure for storing top-level type definitions.
-/// Used for collecting type signature from source code.
-/// Can be converted to `InferenceContext` for type inference in functions.
-pub struct TopLevelContext<'a> {
-    /// List of primitive definitions.
-    pub(super) primitive_defs: Vec<TypeDef<'a>>,
-    /// List of class definitions.
-    pub(super) class_defs: Vec<ClassDef<'a>>,
-    /// List of parametric type definitions.
-    pub(super) parametric_defs: Vec<ParametricDef<'a>>,
-    /// List of type variable definitions.
-    pub(super) var_defs: Vec<VarDef<'a>>,
-    /// Function name to signature mapping.
-    pub(super) fn_table: HashMap<&'a str, FnDef>,
-    /// Type name to type mapping.
-    pub(super) sym_table: HashMap<&'a str, Type>,
-
-    primitives: Vec<Type>,
-    variables: Vec<Type>,
-}
-
-impl<'a> TopLevelContext<'a> {
-    pub fn new(primitive_defs: Vec<TypeDef<'a>>) -> TopLevelContext {
-        let mut sym_table = HashMap::new();
-        let mut primitives = Vec::new();
-        for (i, t) in primitive_defs.iter().enumerate() {
-            primitives.push(TypeEnum::PrimitiveType(PrimitiveId(i)).into());
-            sym_table.insert(t.name, TypeEnum::PrimitiveType(PrimitiveId(i)).into());
-        }
-        TopLevelContext {
-            primitive_defs,
-            class_defs: Vec::new(),
-            parametric_defs: Vec::new(),
-            var_defs: Vec::new(),
-            fn_table: HashMap::new(),
-            sym_table,
-            primitives,
-            variables: Vec::new(),
-        }
-    }
-
-    pub fn add_class(&mut self, def: ClassDef<'a>) -> ClassId {
-        self.sym_table.insert(
-            def.base.name,
-            TypeEnum::ClassType(ClassId(self.class_defs.len())).into(),
-        );
-        self.class_defs.push(def);
-        ClassId(self.class_defs.len() - 1)
-    }
-
-    pub fn add_parametric(&mut self, def: ParametricDef<'a>) -> ParamId {
-        let params = def
-            .params
-            .iter()
-            .map(|&v| Rc::new(TypeEnum::TypeVariable(v)))
-            .collect();
-        self.sym_table.insert(
-            def.base.name,
-            TypeEnum::ParametricType(ParamId(self.parametric_defs.len()), params).into(),
-        );
-        self.parametric_defs.push(def);
-        ParamId(self.parametric_defs.len() - 1)
-    }
-
-    pub fn add_variable(&mut self, def: VarDef<'a>) -> VariableId {
-        self.sym_table.insert(
-            def.name,
-            TypeEnum::TypeVariable(VariableId(self.var_defs.len())).into(),
-        );
-        self.add_variable_private(def)
-    }
-
-    pub fn add_variable_private(&mut self, def: VarDef<'a>) -> VariableId {
-        self.var_defs.push(def);
-        self.variables
-            .push(TypeEnum::TypeVariable(VariableId(self.var_defs.len() - 1)).into());
-        VariableId(self.var_defs.len() - 1)
-    }
-
-    pub fn add_fn(&mut self, name: &'a str, def: FnDef) {
-        self.fn_table.insert(name, def);
-    }
-
-    pub fn get_fn_def(&self, name: &str) -> Option<&FnDef> {
-        self.fn_table.get(name)
-    }
-
-    pub fn get_primitive_def_mut(&mut self, id: PrimitiveId) -> &mut TypeDef<'a> {
-        self.primitive_defs.get_mut(id.0).unwrap()
-    }
-
-    pub fn get_primitive_def(&self, id: PrimitiveId) -> &TypeDef {
-        self.primitive_defs.get(id.0).unwrap()
-    }
-
-    pub fn get_class_def_mut(&mut self, id: ClassId) -> &mut ClassDef<'a> {
-        self.class_defs.get_mut(id.0).unwrap()
-    }
-
-    pub fn get_class_def(&self, id: ClassId) -> &ClassDef {
-        self.class_defs.get(id.0).unwrap()
-    }
-
-    pub fn get_parametric_def_mut(&mut self, id: ParamId) -> &mut ParametricDef<'a> {
-        self.parametric_defs.get_mut(id.0).unwrap()
-    }
-
-    pub fn get_parametric_def(&self, id: ParamId) -> &ParametricDef {
-        self.parametric_defs.get(id.0).unwrap()
-    }
-
-    pub fn get_variable_def_mut(&mut self, id: VariableId) -> &mut VarDef<'a> {
-        self.var_defs.get_mut(id.0).unwrap()
-    }
-
-    pub fn get_variable_def(&self, id: VariableId) -> &VarDef {
-        self.var_defs.get(id.0).unwrap()
-    }
-
-    pub fn get_primitive(&self, id: PrimitiveId) -> Type {
-        self.primitives.get(id.0).unwrap().clone()
-    }
-
-    pub fn get_variable(&self, id: VariableId) -> Type {
-        self.variables.get(id.0).unwrap().clone()
-    }
-
-    pub fn get_type(&self, name: &str) -> Option<Type> {
-        // TODO: handle parametric types
-        self.sym_table.get(name).cloned()
-    }
-}

nac3core/src/expression_inference.rs

@@ -1,922 +0,0 @@
-use crate::context::InferenceContext;
-use crate::inference_core::resolve_call;
-use crate::magic_methods::*;
-use crate::primitives::*;
-use crate::typedef::{Type, TypeEnum::*};
-use rustpython_parser::ast::{
-    Comparison, Comprehension, ComprehensionKind, Expression, ExpressionType, Operator,
-    UnaryOperator,
-};
-use std::convert::TryInto;
-
-type ParserResult = Result<Option<Type>, String>;
-
-pub fn infer_expr<'b: 'a, 'a>(
-    ctx: &mut InferenceContext<'a>,
-    expr: &'b Expression,
-) -> ParserResult {
-    match &expr.node {
-        ExpressionType::Number { value } => infer_constant(ctx, value),
-        ExpressionType::Identifier { name } => infer_identifier(ctx, name),
-        ExpressionType::List { elements } => infer_list(ctx, elements),
-        ExpressionType::Tuple { elements } => infer_tuple(ctx, elements),
-        ExpressionType::Attribute { value, name } => infer_attribute(ctx, value, name),
-        ExpressionType::BoolOp { values, .. } => infer_bool_ops(ctx, values),
-        ExpressionType::Binop { a, b, op } => infer_bin_ops(ctx, op, a, b),
-        ExpressionType::Unop { op, a } => infer_unary_ops(ctx, op, a),
-        ExpressionType::Compare { vals, ops } => infer_compare(ctx, vals, ops),
-        ExpressionType::Call {
-            args,
-            function,
-            keywords,
-        } => {
-            if !keywords.is_empty() {
-                Err("keyword is not supported".into())
-            } else {
-                infer_call(ctx, &args, &function)
-            }
-        }
-        ExpressionType::Subscript { a, b } => infer_subscript(ctx, a, b),
-        ExpressionType::IfExpression { test, body, orelse } => {
-            infer_if_expr(ctx, &test, &body, orelse)
-        }
-        ExpressionType::Comprehension { kind, generators } => match kind.as_ref() {
-            ComprehensionKind::List { element } => {
-                if generators.len() == 1 {
-                    infer_list_comprehension(ctx, element, &generators[0])
-                } else {
-                    Err("only 1 generator statement is supported".into())
-                }
-            }
-            _ => Err("only list comprehension is supported".into()),
-        },
-        ExpressionType::True | ExpressionType::False => Ok(Some(ctx.get_primitive(BOOL_TYPE))),
-        _ => Err("not supported".into()),
-    }
-}
-
-fn infer_constant(
-    ctx: &mut InferenceContext,
-    value: &rustpython_parser::ast::Number,
-) -> ParserResult {
-    use rustpython_parser::ast::Number;
-    match value {
-        Number::Integer { value } => {
-            let int32: Result<i32, _> = value.try_into();
-            if int32.is_ok() {
-                Ok(Some(ctx.get_primitive(INT32_TYPE)))
-            } else {
-                Err("integer out of range".into())
-            }
-        }
-        Number::Float { .. } => Ok(Some(ctx.get_primitive(FLOAT_TYPE))),
-        _ => Err("not supported".into()),
-    }
-}
-
-fn infer_identifier(ctx: &mut InferenceContext, name: &str) -> ParserResult {
-    Ok(Some(ctx.resolve(name)?))
-}
-
-fn infer_list<'b: 'a, 'a>(
-    ctx: &mut InferenceContext<'a>,
-    elements: &'b [Expression],
-) -> ParserResult {
-    if elements.is_empty() {
-        return Ok(Some(ParametricType(LIST_TYPE, vec![BotType.into()]).into()));
-    }
-
-    let mut types = elements.iter().map(|v| infer_expr(ctx, v));
-
-    let head = types.next().unwrap()?;
-    if head.is_none() {
-        return Err("list elements must have some type".into());
-    }
-    for v in types {
-        // TODO: try virtual type...
-        if v? != head {
-            return Err("inhomogeneous list is not allowed".into());
-        }
-    }
-    Ok(Some(ParametricType(LIST_TYPE, vec![head.unwrap()]).into()))
-}
-
-fn infer_tuple<'b: 'a, 'a>(
-    ctx: &mut InferenceContext<'a>,
-    elements: &'b [Expression],
-) -> ParserResult {
-    let types: Result<Option<Vec<_>>, String> =
-        elements.iter().map(|v| infer_expr(ctx, v)).collect();
-    if let Some(t) = types? {
-        Ok(Some(ParametricType(TUPLE_TYPE, t).into()))
-    } else {
-        Err("tuple elements must have some type".into())
-    }
-}
-
-fn infer_attribute<'a>(
-    ctx: &mut InferenceContext<'a>,
-    value: &'a Expression,
-    name: &str,
-) -> ParserResult {
-    let value = infer_expr(ctx, value)?.ok_or_else(|| "no value".to_string())?;
-    if let TypeVariable(_) = value.as_ref() {
-        return Err("no fields for type variable".into());
-    }
-
-    value
-        .get_base(ctx)
-        .and_then(|b| b.fields.get(name).cloned())
-        .map_or_else(|| Err("no such field".to_string()), |v| Ok(Some(v)))
-}
-
-fn infer_bool_ops<'a>(ctx: &mut InferenceContext<'a>, values: &'a [Expression]) -> ParserResult {
-    assert_eq!(values.len(), 2);
-    let left = infer_expr(ctx, &values[0])?.ok_or_else(|| "no value".to_string())?;
-    let right = infer_expr(ctx, &values[1])?.ok_or_else(|| "no value".to_string())?;
-
-    let b = ctx.get_primitive(BOOL_TYPE);
-    if left == b && right == b {
-        Ok(Some(b))
-    } else {
-        Err("bool operands must be bool".into())
-    }
-}
-
-fn infer_bin_ops<'b: 'a, 'a>(
-    ctx: &mut InferenceContext<'a>,
-    op: &Operator,
-    left: &'b Expression,
-    right: &'b Expression,
-) -> ParserResult {
-    let left = infer_expr(ctx, left)?.ok_or_else(|| "no value".to_string())?;
-    let right = infer_expr(ctx, right)?.ok_or_else(|| "no value".to_string())?;
-    let fun = binop_name(op);
-    resolve_call(ctx, Some(left), fun, &[right])
-}
-
-fn infer_unary_ops<'b: 'a, 'a>(
-    ctx: &mut InferenceContext<'a>,
-    op: &UnaryOperator,
-    obj: &'b Expression,
-) -> ParserResult {
-    let ty = infer_expr(ctx, obj)?.ok_or_else(|| "no value".to_string())?;
-    if let UnaryOperator::Not = op {
-        if ty == ctx.get_primitive(BOOL_TYPE) {
-            Ok(Some(ty))
-        } else {
-            Err("logical not must be applied to bool".into())
-        }
-    } else {
-        resolve_call(ctx, Some(ty), unaryop_name(op), &[])
-    }
-}
-
-fn infer_compare<'b: 'a, 'a>(
-    ctx: &mut InferenceContext<'a>,
-    vals: &'b [Expression],
-    ops: &'b [Comparison],
-) -> ParserResult {
-    let types: Result<Option<Vec<_>>, _> = vals.iter().map(|v| infer_expr(ctx, v)).collect();
-    let types = types?;
-    if types.is_none() {
-        return Err("comparison operands must have type".into());
-    }
-    let types = types.unwrap();
-    let boolean = ctx.get_primitive(BOOL_TYPE);
-    let left = &types[..types.len() - 1];
-    let right = &types[1..];
-
-    for ((a, b), op) in left.iter().zip(right.iter()).zip(ops.iter()) {
-        let fun = comparison_name(op).ok_or_else(|| "unsupported comparison".to_string())?;
-        let ty = resolve_call(ctx, Some(a.clone()), fun, &[b.clone()])?;
-        if ty.is_none() || ty.unwrap() != boolean {
-            return Err("comparison result must be boolean".into());
-        }
-    }
-    Ok(Some(boolean))
-}
-
-fn infer_call<'b: 'a, 'a>(
-    ctx: &mut InferenceContext<'a>,
-    args: &'b [Expression],
-    function: &'b Expression,
-) -> ParserResult {
-    // TODO: special handling for int64 constant
-    let types: Result<Option<Vec<_>>, _> = args.iter().map(|v| infer_expr(ctx, v)).collect();
-    let types = types?;
-    if types.is_none() {
-        return Err("function params must have type".into());
-    }
-
-    let (obj, fun) = match &function.node {
-        ExpressionType::Identifier { name } => (None, name),
-        ExpressionType::Attribute { value, name } => (
-            Some(infer_expr(ctx, &value)?.ok_or_else(|| "no value".to_string())?),
-            name,
-        ),
-        _ => return Err("not supported".into()),
-    };
-    resolve_call(ctx, obj, fun.as_str(), &types.unwrap())
-}
-
-fn infer_subscript<'b: 'a, 'a>(
-    ctx: &mut InferenceContext<'a>,
-    a: &'b Expression,
-    b: &'b Expression,
-) -> ParserResult {
-    let a = infer_expr(ctx, a)?.ok_or_else(|| "no value".to_string())?;
-    let t = if let ParametricType(LIST_TYPE, ls) = a.as_ref() {
-        ls[0].clone()
-    } else {
-        return Err("subscript is not supported for types other than list".into());
-    };
-
-    match &b.node {
-        ExpressionType::Slice { elements } => {
-            let int32 = ctx.get_primitive(INT32_TYPE);
-            let types: Result<Option<Vec<_>>, _> = elements
-                .iter()
-                .map(|v| {
-                    if let ExpressionType::None = v.node {
-                        Ok(Some(int32.clone()))
-                    } else {
-                        infer_expr(ctx, v)
-                    }
-                })
-                .collect();
-            let types = types?.ok_or_else(|| "slice must have type".to_string())?;
-            if types.iter().all(|v| v == &int32) {
-                Ok(Some(a))
-            } else {
-                Err("slice must be int32 type".into())
-            }
-        }
-        _ => {
-            let b = infer_expr(ctx, b)?.ok_or_else(|| "no value".to_string())?;
-            if b == ctx.get_primitive(INT32_TYPE) {
-                Ok(Some(t))
-            } else {
-                Err("index must be either slice or int32".into())
-            }
-        }
-    }
-}
-
-fn infer_if_expr<'b: 'a, 'a>(
-    ctx: &mut InferenceContext<'a>,
-    test: &'b Expression,
-    body: &'b Expression,
-    orelse: &'b Expression,
-) -> ParserResult {
-    let test = infer_expr(ctx, test)?.ok_or_else(|| "no value".to_string())?;
-    if test != ctx.get_primitive(BOOL_TYPE) {
-        return Err("test should be bool".into());
-    }
-
-    let body = infer_expr(ctx, body)?;
-    let orelse = infer_expr(ctx, orelse)?;
-    if body.as_ref() == orelse.as_ref() {
-        Ok(body)
-    } else {
-        Err("divergent type".into())
-    }
-}
-
-fn infer_simple_binding<'a: 'b, 'b>(
-    ctx: &mut InferenceContext<'b>,
-    name: &'a Expression,
-    ty: Type,
-) -> Result<(), String> {
-    match &name.node {
-        ExpressionType::Identifier { name } => {
-            if name == "_" {
-                Ok(())
-            } else if ctx.defined(name.as_str()) {
-                Err("duplicated naming".into())
-            } else {
-                ctx.assign(name.as_str(), ty)?;
-                Ok(())
-            }
-        }
-        ExpressionType::Tuple { elements } => {
-            if let ParametricType(TUPLE_TYPE, ls) = ty.as_ref() {
-                if elements.len() == ls.len() {
-                    for (a, b) in elements.iter().zip(ls.iter()) {
-                        infer_simple_binding(ctx, a, b.clone())?;
-                    }
-                    Ok(())
-                } else {
-                    Err("different length".into())
-                }
-            } else {
-                Err("not supported".into())
-            }
-        }
-        _ => Err("not supported".into()),
-    }
-}
-
-fn infer_list_comprehension<'b: 'a, 'a>(
-    ctx: &mut InferenceContext<'a>,
-    element: &'b Expression,
-    comprehension: &'b Comprehension,
-) -> ParserResult {
-    if comprehension.is_async {
-        return Err("async is not supported".into());
-    }
-
-    let iter = infer_expr(ctx, &comprehension.iter)?.ok_or_else(|| "no value".to_string())?;
-    if let ParametricType(LIST_TYPE, ls) = iter.as_ref() {
-        ctx.with_scope(|ctx| {
-            infer_simple_binding(ctx, &comprehension.target, ls[0].clone())?;
-
-            let boolean = ctx.get_primitive(BOOL_TYPE);
-            for test in comprehension.ifs.iter() {
-                let result =
-                    infer_expr(ctx, test)?.ok_or_else(|| "no value in test".to_string())?;
-                if result != boolean {
-                    return Err("test must be bool".into());
-                }
-            }
-            let result = infer_expr(ctx, element)?.ok_or_else(|| "no value")?;
-            Ok(Some(ParametricType(LIST_TYPE, vec![result]).into()))
-        })
-        .1
-    } else {
-        Err("iteration is supported for list only".into())
-    }
-}
-
-#[cfg(test)]
-mod test {
-    use super::*;
-    use crate::context::*;
-    use crate::typedef::*;
-    use rustpython_parser::parser::parse_expression;
-    use std::collections::HashMap;
-    use std::rc::Rc;
-
-    fn get_inference_context(ctx: TopLevelContext) -> InferenceContext {
-        InferenceContext::new(ctx, Box::new(|_| Err("unbounded identifier".into())))
-    }
-
-    #[test]
-    fn test_constants() {
-        let ctx = basic_ctx();
-        let mut ctx = get_inference_context(ctx);
-
-        let ast = parse_expression("123").unwrap();
-        let result = infer_expr(&mut ctx, &ast);
-        assert_eq!(result.unwrap().unwrap(), ctx.get_primitive(INT32_TYPE));
-
-        let ast = parse_expression("2147483647").unwrap();
-        let result = infer_expr(&mut ctx, &ast);
-        assert_eq!(result.unwrap().unwrap(), ctx.get_primitive(INT32_TYPE));
-
-        let ast = parse_expression("2147483648").unwrap();
-        let result = infer_expr(&mut ctx, &ast);
-        assert_eq!(result, Err("integer out of range".into()));
-        //
-        // let ast = parse_expression("2147483648").unwrap();
-        // let result = infer_expr(&mut ctx, &ast);
-        // assert_eq!(result.unwrap().unwrap(), ctx.get_primitive(INT64_TYPE));
-
-        // let ast = parse_expression("9223372036854775807").unwrap();
-        // let result = infer_expr(&mut ctx, &ast);
-        // assert_eq!(result.unwrap().unwrap(), ctx.get_primitive(INT64_TYPE));
-
-        // let ast = parse_expression("9223372036854775808").unwrap();
-        // let result = infer_expr(&mut ctx, &ast);
-        // assert_eq!(result, Err("integer out of range".into()));
-
-        let ast = parse_expression("123.456").unwrap();
-        let result = infer_expr(&mut ctx, &ast);
-        assert_eq!(result.unwrap().unwrap(), ctx.get_primitive(FLOAT_TYPE));
-
-        let ast = parse_expression("True").unwrap();
-        let result = infer_expr(&mut ctx, &ast);
-        assert_eq!(result.unwrap().unwrap(), ctx.get_primitive(BOOL_TYPE));
-
-        let ast = parse_expression("False").unwrap();
-        let result = infer_expr(&mut ctx, &ast);
-        assert_eq!(result.unwrap().unwrap(), ctx.get_primitive(BOOL_TYPE));
-    }
-
-    #[test]
-    fn test_identifier() {
-        let ctx = basic_ctx();
-        let mut ctx = get_inference_context(ctx);
-        ctx.assign("abc", ctx.get_primitive(INT32_TYPE)).unwrap();
-
-        let ast = parse_expression("abc").unwrap();
-        let result = infer_expr(&mut ctx, &ast);
-        assert_eq!(result.unwrap().unwrap(), ctx.get_primitive(INT32_TYPE));
-
-        let ast = parse_expression("ab").unwrap();
-        let result = infer_expr(&mut ctx, &ast);
-        assert_eq!(result, Err("unbounded identifier".into()));
-    }
-
-    #[test]
-    fn test_list() {
-        let mut ctx = basic_ctx();
-        ctx.add_fn(
-            "foo",
-            FnDef {
-                args: vec![],
-                result: None,
-            },
-        );
-        let mut ctx = get_inference_context(ctx);
-        ctx.assign("abc", ctx.get_primitive(INT32_TYPE)).unwrap();
-        // def is reserved...
-        ctx.assign("efg", ctx.get_primitive(INT32_TYPE)).unwrap();
-        ctx.assign("xyz", ctx.get_primitive(FLOAT_TYPE)).unwrap();
-
-        let ast = parse_expression("[]").unwrap();
-        let result = infer_expr(&mut ctx, &ast);
-        assert_eq!(
-            result.unwrap().unwrap(),
-            ParametricType(LIST_TYPE, vec![BotType.into()]).into()
-        );
-
-        let ast = parse_expression("[abc]").unwrap();
-        let result = infer_expr(&mut ctx, &ast);
-        assert_eq!(
-            result.unwrap().unwrap(),
-            ParametricType(LIST_TYPE, vec![ctx.get_primitive(INT32_TYPE)]).into()
-        );
-
-        let ast = parse_expression("[abc, efg]").unwrap();
-        let result = infer_expr(&mut ctx, &ast);
-        assert_eq!(
-            result.unwrap().unwrap(),
-            ParametricType(LIST_TYPE, vec![ctx.get_primitive(INT32_TYPE)]).into()
-        );
-
-        let ast = parse_expression("[abc, efg, xyz]").unwrap();
-        let result = infer_expr(&mut ctx, &ast);
-        assert_eq!(result, Err("inhomogeneous list is not allowed".into()));
-
-        let ast = parse_expression("[foo()]").unwrap();
-        let result = infer_expr(&mut ctx, &ast);
-        assert_eq!(result, Err("list elements must have some type".into()));
-    }
-
-    #[test]
-    fn test_tuple() {
-        let mut ctx = basic_ctx();
-        ctx.add_fn(
-            "foo",
-            FnDef {
-                args: vec![],
-                result: None,
-            },
-        );
-        let mut ctx = get_inference_context(ctx);
-        ctx.assign("abc", ctx.get_primitive(INT32_TYPE)).unwrap();
-        ctx.assign("efg", ctx.get_primitive(FLOAT_TYPE)).unwrap();
-
-        let ast = parse_expression("(abc, efg)").unwrap();
-        let result = infer_expr(&mut ctx, &ast);
-        assert_eq!(
-            result.unwrap().unwrap(),
-            ParametricType(
-                TUPLE_TYPE,
-                vec![ctx.get_primitive(INT32_TYPE), ctx.get_primitive(FLOAT_TYPE)]
-            )
-            .into()
-        );
-
-        let ast = parse_expression("(abc, efg, foo())").unwrap();
-        let result = infer_expr(&mut ctx, &ast);
-        assert_eq!(result, Err("tuple elements must have some type".into()));
-    }
-
-    #[test]
-    fn test_attribute() {
-        let mut ctx = basic_ctx();
-        ctx.add_fn(
-            "none",
-            FnDef {
-                args: vec![],
-                result: None,
-            },
-        );
-        let int32 = ctx.get_primitive(INT32_TYPE);
-        let float = ctx.get_primitive(FLOAT_TYPE);
-
-        let foo = ctx.add_class(ClassDef {
-            base: TypeDef {
-                name: "Foo",
-                fields: HashMap::new(),
-                methods: HashMap::new(),
-            },
-            parents: vec![],
-        });
-        let foo_def = ctx.get_class_def_mut(foo);
-        foo_def.base.fields.insert("a", int32.clone());
-        foo_def.base.fields.insert("b", ClassType(foo).into());
-        foo_def.base.fields.insert("c", int32.clone());
-
-        let bar = ctx.add_class(ClassDef {
-            base: TypeDef {
-                name: "Bar",
-                fields: HashMap::new(),
-                methods: HashMap::new(),
-            },
-            parents: vec![],
-        });
-        let bar_def = ctx.get_class_def_mut(bar);
-        bar_def.base.fields.insert("a", int32);
-        bar_def.base.fields.insert("b", ClassType(bar).into());
-        bar_def.base.fields.insert("c", float);
-
-        let v0 = ctx.add_variable(VarDef {
-            name: "v0",
-            bound: vec![],
-        });
-
-        let v1 = ctx.add_variable(VarDef {
-            name: "v1",
-            bound: vec![ClassType(foo).into(), ClassType(bar).into()],
-        });
-
-        let mut ctx = get_inference_context(ctx);
-        ctx.assign("foo", Rc::new(ClassType(foo))).unwrap();
-        ctx.assign("bar", Rc::new(ClassType(bar))).unwrap();
-        ctx.assign("foobar", Rc::new(VirtualClassType(foo)))
-            .unwrap();
-        ctx.assign("v0", ctx.get_variable(v0)).unwrap();
-        ctx.assign("v1", ctx.get_variable(v1)).unwrap();
-        ctx.assign("bot", Rc::new(BotType)).unwrap();
-
-        let ast = parse_expression("foo.a").unwrap();
-        let result = infer_expr(&mut ctx, &ast);
-        assert_eq!(result.unwrap().unwrap(), ctx.get_primitive(INT32_TYPE));
-
-        let ast = parse_expression("foo.d").unwrap();
-        let result = infer_expr(&mut ctx, &ast);
-        assert_eq!(result, Err("no such field".into()));
-
-        let ast = parse_expression("foobar.a").unwrap();
-        let result = infer_expr(&mut ctx, &ast);
-        assert_eq!(result.unwrap().unwrap(), ctx.get_primitive(INT32_TYPE));
-
-        let ast = parse_expression("v0.a").unwrap();
-        let result = infer_expr(&mut ctx, &ast);
-        assert_eq!(result, Err("no fields for type variable".into()));
-
-        let ast = parse_expression("v1.a").unwrap();
-        let result = infer_expr(&mut ctx, &ast);
-        assert_eq!(result, Err("no fields for type variable".into()));
-
-        let ast = parse_expression("none().a").unwrap();
-        let result = infer_expr(&mut ctx, &ast);
-        assert_eq!(result, Err("no value".into()));
-
-        let ast = parse_expression("bot.a").unwrap();
-        let result = infer_expr(&mut ctx, &ast);
-        assert_eq!(result, Err("no such field".into()));
-    }
-
-    #[test]
-    fn test_bool_ops() {
-        let mut ctx = basic_ctx();
-        ctx.add_fn(
-            "none",
-            FnDef {
-                args: vec![],
-                result: None,
-            },
-        );
-        let mut ctx = get_inference_context(ctx);
-
-        let ast = parse_expression("True and False").unwrap();
-        let result = infer_expr(&mut ctx, &ast);
-        assert_eq!(result.unwrap().unwrap(), ctx.get_primitive(BOOL_TYPE));
-
-        let ast = parse_expression("True and none()").unwrap();
-        let result = infer_expr(&mut ctx, &ast);
-        assert_eq!(result, Err("no value".into()));
-
-        let ast = parse_expression("True and 123").unwrap();
-        let result = infer_expr(&mut ctx, &ast);
-        assert_eq!(result, Err("bool operands must be bool".into()));
-    }
-
-    #[test]
-    fn test_bin_ops() {
-        let mut ctx = basic_ctx();
-        let v0 = ctx.add_variable(VarDef {
-            name: "v0",
-            bound: vec![ctx.get_primitive(INT32_TYPE), ctx.get_primitive(INT64_TYPE)],
-        });
-        let mut ctx = get_inference_context(ctx);
-        ctx.assign("a", TypeVariable(v0).into()).unwrap();
-
-        let ast = parse_expression("1 + 2 + 3").unwrap();
-        let result = infer_expr(&mut ctx, &ast);
-        assert_eq!(result.unwrap().unwrap(), ctx.get_primitive(INT32_TYPE));
-
-        let ast = parse_expression("a + a + a").unwrap();
-        let result = infer_expr(&mut ctx, &ast);
-        assert_eq!(result, Err("not supported".into()));
-    }
-
-    #[test]
-    fn test_unary_ops() {
-        let mut ctx = basic_ctx();
-        let v0 = ctx.add_variable(VarDef {
-            name: "v0",
-            bound: vec![ctx.get_primitive(INT32_TYPE), ctx.get_primitive(INT64_TYPE)],
-        });
-        let mut ctx = get_inference_context(ctx);
-        ctx.assign("a", TypeVariable(v0).into()).unwrap();
-
-        let ast = parse_expression("-(123)").unwrap();
-        let result = infer_expr(&mut ctx, &ast);
-        assert_eq!(result.unwrap().unwrap(), ctx.get_primitive(INT32_TYPE));
-
-        let ast = parse_expression("-a").unwrap();
-        let result = infer_expr(&mut ctx, &ast);
-        assert_eq!(result, Err("not supported".into()));
-
-        let ast = parse_expression("not True").unwrap();
-        let result = infer_expr(&mut ctx, &ast);
-        assert_eq!(result.unwrap().unwrap(), ctx.get_primitive(BOOL_TYPE));
-
-        let ast = parse_expression("not (1)").unwrap();
-        let result = infer_expr(&mut ctx, &ast);
-        assert_eq!(result, Err("logical not must be applied to bool".into()));
-    }
-
-    #[test]
-    fn test_compare() {
-        let mut ctx = basic_ctx();
-        let v0 = ctx.add_variable(VarDef {
-            name: "v0",
-            bound: vec![ctx.get_primitive(INT32_TYPE), ctx.get_primitive(INT64_TYPE)],
-        });
-        let mut ctx = get_inference_context(ctx);
-        ctx.assign("a", TypeVariable(v0).into()).unwrap();
-
-        let ast = parse_expression("a == a == a").unwrap();
-        let result = infer_expr(&mut ctx, &ast);
-        assert_eq!(result, Err("not supported".into()));
-
-        let ast = parse_expression("a == a == 1").unwrap();
-        let result = infer_expr(&mut ctx, &ast);
-        assert_eq!(result, Err("not supported".into()));
-
-        let ast = parse_expression("True > False").unwrap();
-        let result = infer_expr(&mut ctx, &ast);
-        assert_eq!(result, Err("no such function".into()));
-
-        let ast = parse_expression("True in False").unwrap();
-        let result = infer_expr(&mut ctx, &ast);
-        assert_eq!(result, Err("unsupported comparison".into()));
-    }
-
-    #[test]
-    fn test_call() {
-        let mut ctx = basic_ctx();
-        ctx.add_fn(
-            "none",
-            FnDef {
-                args: vec![],
-                result: None,
-            },
-        );
-
-        let foo = ctx.add_class(ClassDef {
-            base: TypeDef {
-                name: "Foo",
-                fields: HashMap::new(),
-                methods: HashMap::new(),
-            },
-            parents: vec![],
-        });
-        let foo_def = ctx.get_class_def_mut(foo);
-        foo_def.base.methods.insert(
-            "a",
-            FnDef {
-                args: vec![],
-                result: Some(Rc::new(ClassType(foo))),
-            },
-        );
-
-        let bar = ctx.add_class(ClassDef {
-            base: TypeDef {
-                name: "Bar",
-                fields: HashMap::new(),
-                methods: HashMap::new(),
-            },
-            parents: vec![],
-        });
-        let bar_def = ctx.get_class_def_mut(bar);
-        bar_def.base.methods.insert(
-            "a",
-            FnDef {
-                args: vec![],
-                result: Some(Rc::new(ClassType(bar))),
-            },
-        );
-
-        let v0 = ctx.add_variable(VarDef {
-            name: "v0",
-            bound: vec![],
-        });
-        let v1 = ctx.add_variable(VarDef {
-            name: "v1",
-            bound: vec![ClassType(foo).into(), ClassType(bar).into()],
-        });
-        let v2 = ctx.add_variable(VarDef {
-            name: "v2",
-            bound: vec![
-                ClassType(foo).into(),
-                ClassType(bar).into(),
-                ctx.get_primitive(INT32_TYPE),
-            ],
-        });
-        let mut ctx = get_inference_context(ctx);
-        ctx.assign("foo", Rc::new(ClassType(foo))).unwrap();
-        ctx.assign("bar", Rc::new(ClassType(bar))).unwrap();
-        ctx.assign("foobar", Rc::new(VirtualClassType(foo)))
-            .unwrap();
-        ctx.assign("v0", ctx.get_variable(v0)).unwrap();
-        ctx.assign("v1", ctx.get_variable(v1)).unwrap();
-        ctx.assign("v2", ctx.get_variable(v2)).unwrap();
-        ctx.assign("bot", Rc::new(BotType)).unwrap();
-
-        let ast = parse_expression("foo.a()").unwrap();
-        let result = infer_expr(&mut ctx, &ast);
-        assert_eq!(result.unwrap().unwrap(), ClassType(foo).into());
-
-        let ast = parse_expression("v1.a()").unwrap();
-        let result = infer_expr(&mut ctx, &ast);
-        assert_eq!(result, Err("not supported".into()));
-
-        let ast = parse_expression("foobar.a()").unwrap();
-        let result = infer_expr(&mut ctx, &ast);
-        assert_eq!(result.unwrap().unwrap(), ClassType(foo).into());
-
-        let ast = parse_expression("none().a()").unwrap();
-        let result = infer_expr(&mut ctx, &ast);
-        assert_eq!(result, Err("no value".into()));
-
-        let ast = parse_expression("bot.a()").unwrap();
-        let result = infer_expr(&mut ctx, &ast);
-        assert_eq!(result, Err("not supported".into()));
-
-        let ast = parse_expression("[][0].a()").unwrap();
-        let result = infer_expr(&mut ctx, &ast);
-        assert_eq!(result, Err("not supported".into()));
-    }
-
-    #[test]
-    fn infer_subscript() {
-        let mut ctx = basic_ctx();
-        ctx.add_fn(
-            "none",
-            FnDef {
-                args: vec![],
-                result: None,
-            },
-        );
-        let mut ctx = get_inference_context(ctx);
-
-        let ast = parse_expression("[1, 2, 3][0]").unwrap();
-        let result = infer_expr(&mut ctx, &ast);
-        assert_eq!(result.unwrap().unwrap(), ctx.get_primitive(INT32_TYPE));
-
-        let ast = parse_expression("[[1]][0][0]").unwrap();
-        let result = infer_expr(&mut ctx, &ast);
-        assert_eq!(result.unwrap().unwrap(), ctx.get_primitive(INT32_TYPE));
-
-        let ast = parse_expression("[1, 2, 3][1:2]").unwrap();
-        let result = infer_expr(&mut ctx, &ast);
-        assert_eq!(
-            result.unwrap().unwrap(),
-            ParametricType(LIST_TYPE, vec![ctx.get_primitive(INT32_TYPE)]).into()
-        );
-
-        let ast = parse_expression("[1, 2, 3][1:2:2]").unwrap();
-        let result = infer_expr(&mut ctx, &ast);
-        assert_eq!(
-            result.unwrap().unwrap(),
-            ParametricType(LIST_TYPE, vec![ctx.get_primitive(INT32_TYPE)]).into()
-        );
-
-        let ast = parse_expression("[1, 2, 3][1:1.2]").unwrap();
-        let result = infer_expr(&mut ctx, &ast);
-        assert_eq!(result, Err("slice must be int32 type".into()));
-
-        let ast = parse_expression("[1, 2, 3][1:none()]").unwrap();
-        let result = infer_expr(&mut ctx, &ast);
-        assert_eq!(result, Err("slice must have type".into()));
-
-        let ast = parse_expression("[1, 2, 3][1.2]").unwrap();
-        let result = infer_expr(&mut ctx, &ast);
-        assert_eq!(result, Err("index must be either slice or int32".into()));
-
-        let ast = parse_expression("[1, 2, 3][none()]").unwrap();
-        let result = infer_expr(&mut ctx, &ast);
-        assert_eq!(result, Err("no value".into()));
-
-        let ast = parse_expression("none()[1.2]").unwrap();
-        let result = infer_expr(&mut ctx, &ast);
-        assert_eq!(result, Err("no value".into()));
-
-        let ast = parse_expression("123[1]").unwrap();
-        let result = infer_expr(&mut ctx, &ast);
-        assert_eq!(
-            result,
-            Err("subscript is not supported for types other than list".into())
-        );
-    }
-
-    #[test]
-    fn test_if_expr() {
-        let mut ctx = basic_ctx();
-        ctx.add_fn(
-            "none",
-            FnDef {
-                args: vec![],
-                result: None,
-            },
-        );
-        let mut ctx = get_inference_context(ctx);
-
-        let ast = parse_expression("1 if True else 0").unwrap();
-        let result = infer_expr(&mut ctx, &ast);
-        assert_eq!(result.unwrap().unwrap(), ctx.get_primitive(INT32_TYPE));
-
-        let ast = parse_expression("none() if True else none()").unwrap();
-        let result = infer_expr(&mut ctx, &ast);
-        assert_eq!(result.unwrap(), None);
-
-        let ast = parse_expression("none() if 1 else none()").unwrap();
-        let result = infer_expr(&mut ctx, &ast);
-        assert_eq!(result, Err("test should be bool".into()));
-
-        let ast = parse_expression("1 if True else none()").unwrap();
-        let result = infer_expr(&mut ctx, &ast);
-        assert_eq!(result, Err("divergent type".into()));
-    }
-
-    #[test]
-    fn test_list_comp() {
-        let mut ctx = basic_ctx();
-        ctx.add_fn(
-            "none",
-            FnDef {
-                args: vec![],
-                result: None,
-            },
-        );
-        let int32 = ctx.get_primitive(INT32_TYPE);
-        let mut ctx = get_inference_context(ctx);
-        ctx.assign("z", int32.clone()).unwrap();
-
-        let ast = parse_expression("[x for x in [(1, 2), (2, 3), (3, 4)]][0]").unwrap();
-        let result = infer_expr(&mut ctx, &ast);
-        assert_eq!(
-            result.unwrap().unwrap(),
-            ParametricType(TUPLE_TYPE, vec![int32.clone(), int32.clone()]).into()
-        );
-
-        let ast = parse_expression("[x for (x, y) in [(1, 2), (2, 3), (3, 4)]][0]").unwrap();
-        let result = infer_expr(&mut ctx, &ast);
-        assert_eq!(result.unwrap().unwrap(), int32);
-
-        let ast =
-            parse_expression("[x for (x, y) in [(1, 2), (2, 3), (3, 4)] if x > 0][0]").unwrap();
-        let result = infer_expr(&mut ctx, &ast);
-        assert_eq!(result.unwrap().unwrap(), int32);
-
-        let ast = parse_expression("[x for (x, y) in [(1, 2), (2, 3), (3, 4)] if x][0]").unwrap();
-        let result = infer_expr(&mut ctx, &ast);
-        assert_eq!(result, Err("test must be bool".into()));
-
-        let ast = parse_expression("[y for x in []][0]").unwrap();
-        let result = infer_expr(&mut ctx, &ast);
-        assert_eq!(result, Err("unbounded identifier".into()));
-
-        let ast = parse_expression("[none() for x in []][0]").unwrap();
-        let result = infer_expr(&mut ctx, &ast);
-        assert_eq!(result, Err("no value".into()));
-
-        let ast = parse_expression("[z for z in []][0]").unwrap();
-        let result = infer_expr(&mut ctx, &ast);
-        assert_eq!(result, Err("duplicated naming".into()));
-
-        let ast = parse_expression("[x for x in [] for y in []]").unwrap();
-        let result = infer_expr(&mut ctx, &ast);
-        assert_eq!(
-            result,
-            Err("only 1 generator statement is supported".into())
-        );
-    }
-}

nac3core/src/inference_core.rs

@@ -1,525 +0,0 @@
-use crate::context::InferenceContext;
-use crate::typedef::{TypeEnum::*, *};
-use std::collections::HashMap;
-
-fn find_subst(
-    ctx: &InferenceContext,
-    valuation: &Option<(VariableId, Type)>,
-    sub: &mut HashMap<VariableId, Type>,
-    mut a: Type,
-    mut b: Type,
-) -> Result<(), String> {
-    // TODO: fix error messages later
-    if let TypeVariable(id) = a.as_ref() {
-        if let Some((assumption_id, t)) = valuation {
-            if assumption_id == id {
-                a = t.clone();
-            }
-        }
-    }
-
-    let mut substituted = false;
-    if let TypeVariable(id) = b.as_ref() {
-        if let Some(c) = sub.get(&id) {
-            b = c.clone();
-            substituted = true;
-        }
-    }
-
-    match (a.as_ref(), b.as_ref()) {
-        (BotType, _) => Ok(()),
-        (TypeVariable(id_a), TypeVariable(id_b)) => {
-            if substituted {
-                return if id_a == id_b {
-                    Ok(())
-                } else {
-                    Err("different variables".to_string())
-                };
-            }
-            let v_a = ctx.get_variable_def(*id_a);
-            let v_b = ctx.get_variable_def(*id_b);
-            if !v_b.bound.is_empty() {
-                if v_a.bound.is_empty() {
-                    return Err("unbounded a".to_string());
-                } else {
-                    let diff: Vec<_> = v_a
-                        .bound
-                        .iter()
-                        .filter(|x| !v_b.bound.contains(x))
-                        .collect();
-                    if !diff.is_empty() {
-                        return Err("different domain".to_string());
-                    }
-                }
-            }
-            sub.insert(*id_b, a.clone());
-            Ok(())
-        }
-        (TypeVariable(id_a), _) => {
-            let v_a = ctx.get_variable_def(*id_a);
-            if v_a.bound.len() == 1 && v_a.bound[0].as_ref() == b.as_ref() {
-                Ok(())
-            } else {
-                Err("different domain".to_string())
-            }
-        }
-        (_, TypeVariable(id_b)) => {
-            let v_b = ctx.get_variable_def(*id_b);
-            if v_b.bound.is_empty() || v_b.bound.contains(&a) {
-                sub.insert(*id_b, a.clone());
-                Ok(())
-            } else {
-                Err("different domain".to_string())
-            }
-        }
-        (_, VirtualClassType(id_b)) => {
-            let mut parents;
-            match a.as_ref() {
-                ClassType(id_a) => {
-                    parents = [*id_a].to_vec();
-                }
-                VirtualClassType(id_a) => {
-                    parents = [*id_a].to_vec();
-                }
-                _ => {
-                    return Err("cannot substitute non-class type into virtual class".to_string());
-                }
-            };
-            while !parents.is_empty() {
-                if *id_b == parents[0] {
-                    return Ok(());
-                }
-                let c = ctx.get_class_def(parents.remove(0));
-                parents.extend_from_slice(&c.parents);
-            }
-            Err("not subtype".to_string())
-        }
-        (ParametricType(id_a, param_a), ParametricType(id_b, param_b)) => {
-            if id_a != id_b || param_a.len() != param_b.len() {
-                Err("different parametric types".to_string())
-            } else {
-                for (x, y) in param_a.iter().zip(param_b.iter()) {
-                    find_subst(ctx, valuation, sub, x.clone(), y.clone())?;
-                }
-                Ok(())
-            }
-        }
-        (_, _) => {
-            if a == b {
-                Ok(())
-            } else {
-                Err("not equal".to_string())
-            }
-        }
-    }
-}
-
-fn resolve_call_rec(
-    ctx: &InferenceContext,
-    valuation: &Option<(VariableId, Type)>,
-    obj: Option<Type>,
-    func: &str,
-    args: &[Type],
-) -> Result<Option<Type>, String> {
-    let mut subst = obj
-        .as_ref()
-        .map(|v| v.get_subst(ctx))
-        .unwrap_or_else(HashMap::new);
-
-    let fun = match &obj {
-        Some(obj) => {
-            let base = match obj.as_ref() {
-                PrimitiveType(id) => &ctx.get_primitive_def(*id),
-                ClassType(id) | VirtualClassType(id) => &ctx.get_class_def(*id).base,
-                ParametricType(id, _) => &ctx.get_parametric_def(*id).base,
-                _ => return Err("not supported".to_string()),
-            };
-            base.methods.get(func)
-        }
-        None => ctx.get_fn_def(func),
-    }
-    .ok_or_else(|| "no such function".to_string())?;
-
-    if args.len() != fun.args.len() {
-        return Err("incorrect parameter number".to_string());
-    }
-    for (a, b) in args.iter().zip(fun.args.iter()) {
-        find_subst(ctx, valuation, &mut subst, a.clone(), b.clone())?;
-    }
-    let result = fun.result.as_ref().map(|v| v.subst(&subst));
-    Ok(result.map(|result| {
-        if let SelfType = result {
-            obj.unwrap()
-        } else {
-            result.into()
-        }
-    }))
-}
-
-pub fn resolve_call(
-    ctx: &InferenceContext,
-    obj: Option<Type>,
-    func: &str,
-    args: &[Type],
-) -> Result<Option<Type>, String> {
-    resolve_call_rec(ctx, &None, obj, func, args)
-}
-
-#[cfg(test)]
-mod tests {
-    use super::*;
-    use crate::context::TopLevelContext;
-    use crate::primitives::*;
-    use std::rc::Rc;
-
-    fn get_inference_context(ctx: TopLevelContext) -> InferenceContext {
-        InferenceContext::new(ctx, Box::new(|_| Err("unbounded identifier".into())))
-    }
-
-    #[test]
-    fn test_simple_generic() {
-        let mut ctx = basic_ctx();
-        let v1 = ctx.add_variable(VarDef {
-            name: "V1",
-            bound: vec![ctx.get_primitive(INT32_TYPE), ctx.get_primitive(FLOAT_TYPE)],
-        });
-        let v1 = ctx.get_variable(v1);
-        let v2 = ctx.add_variable(VarDef {
-            name: "V2",
-            bound: vec![
-                ctx.get_primitive(BOOL_TYPE),
-                ctx.get_primitive(INT32_TYPE),
-                ctx.get_primitive(FLOAT_TYPE),
-            ],
-        });
-        let v2 = ctx.get_variable(v2);
-        let ctx = get_inference_context(ctx);
-
-        assert_eq!(
-            resolve_call(&ctx, None, "int32", &[ctx.get_primitive(FLOAT_TYPE)]),
-            Ok(Some(ctx.get_primitive(INT32_TYPE)))
-        );
-
-        assert_eq!(
-            resolve_call(&ctx, None, "int32", &[ctx.get_primitive(INT32_TYPE)],),
-            Ok(Some(ctx.get_primitive(INT32_TYPE)))
-        );
-
-        assert_eq!(
-            resolve_call(&ctx, None, "float", &[ctx.get_primitive(INT32_TYPE)]),
-            Ok(Some(ctx.get_primitive(FLOAT_TYPE)))
-        );
-
-        assert_eq!(
-            resolve_call(&ctx, None, "float", &[ctx.get_primitive(BOOL_TYPE)]),
-            Err("different domain".to_string())
-        );
-
-        assert_eq!(
-            resolve_call(&ctx, None, "float", &[]),
-            Err("incorrect parameter number".to_string())
-        );
-
-        assert_eq!(
-            resolve_call(&ctx, None, "float", &[v1]),
-            Ok(Some(ctx.get_primitive(FLOAT_TYPE)))
-        );
-
-        assert_eq!(
-            resolve_call(&ctx, None, "float", &[v2]),
-            Err("different domain".to_string())
-        );
-    }
-
-    #[test]
-    fn test_methods() {
-        let mut ctx = basic_ctx();
-
-        let v0 = ctx.add_variable(VarDef {
-            name: "V0",
-            bound: vec![],
-        });
-        let v0 = ctx.get_variable(v0);
-
-        let int32 = ctx.get_primitive(INT32_TYPE);
-        let int64 = ctx.get_primitive(INT64_TYPE);
-        let ctx = get_inference_context(ctx);
-
-        // simple cases
-        assert_eq!(
-            resolve_call(&ctx, Some(int32.clone()), "__add__", &[int32.clone()]),
-            Ok(Some(int32.clone()))
-        );
-
-        assert_ne!(
-            resolve_call(&ctx, Some(int32.clone()), "__add__", &[int32.clone()]),
-            Ok(Some(int64.clone()))
-        );
-
-        assert_eq!(
-            resolve_call(&ctx, Some(int32), "__add__", &[int64]),
-            Err("not equal".to_string())
-        );
-
-        // with type variables
-        assert_eq!(
-            resolve_call(&ctx, Some(v0.clone()), "__add__", &[v0.clone()]),
-            Err("not supported".into())
-        );
-    }
-
-    #[test]
-    fn test_multi_generic() {
-        let mut ctx = basic_ctx();
-        let v0 = ctx.add_variable(VarDef {
-            name: "V0",
-            bound: vec![],
-        });
-        let v0 = ctx.get_variable(v0);
-        let v1 = ctx.add_variable(VarDef {
-            name: "V1",
-            bound: vec![],
-        });
-        let v1 = ctx.get_variable(v1);
-        let v2 = ctx.add_variable(VarDef {
-            name: "V2",
-            bound: vec![],
-        });
-        let v2 = ctx.get_variable(v2);
-        let v3 = ctx.add_variable(VarDef {
-            name: "V3",
-            bound: vec![],
-        });
-        let v3 = ctx.get_variable(v3);
-
-        ctx.add_fn(
-            "foo",
-            FnDef {
-                args: vec![v0.clone(), v0.clone(), v1.clone()],
-                result: Some(v0.clone()),
-            },
-        );
-
-        ctx.add_fn(
-            "foo1",
-            FnDef {
-                args: vec![ParametricType(TUPLE_TYPE, vec![v0.clone(), v0.clone(), v1]).into()],
-                result: Some(v0),
-            },
-        );
-        let ctx = get_inference_context(ctx);
-
-        assert_eq!(
-            resolve_call(&ctx, None, "foo", &[v2.clone(), v2.clone(), v2.clone()]),
-            Ok(Some(v2.clone()))
-        );
-        assert_eq!(
-            resolve_call(&ctx, None, "foo", &[v2.clone(), v2.clone(), v3.clone()]),
-            Ok(Some(v2.clone()))
-        );
-        assert_eq!(
-            resolve_call(&ctx, None, "foo", &[v2.clone(), v3.clone(), v3.clone()]),
-            Err("different variables".to_string())
-        );
-
-        assert_eq!(
-            resolve_call(
-                &ctx,
-                None,
-                "foo1",
-                &[ParametricType(TUPLE_TYPE, vec![v2.clone(), v2.clone(), v2.clone()]).into()]
-            ),
-            Ok(Some(v2.clone()))
-        );
-        assert_eq!(
-            resolve_call(
-                &ctx,
-                None,
-                "foo1",
-                &[ParametricType(TUPLE_TYPE, vec![v2.clone(), v2.clone(), v3.clone()]).into()]
-            ),
-            Ok(Some(v2.clone()))
-        );
-        assert_eq!(
-            resolve_call(
-                &ctx,
-                None,
-                "foo1",
-                &[ParametricType(TUPLE_TYPE, vec![v2, v3.clone(), v3]).into()]
-            ),
-            Err("different variables".to_string())
-        );
-    }
-
-    #[test]
-    fn test_class_generics() {
-        let mut ctx = basic_ctx();
-
-        let list = ctx.get_parametric_def_mut(LIST_TYPE);
-        let t = Rc::new(TypeVariable(list.params[0]));
-        list.base.methods.insert(
-            "head",
-            FnDef {
-                args: vec![],
-                result: Some(t.clone()),
-            },
-        );
-        list.base.methods.insert(
-            "append",
-            FnDef {
-                args: vec![t],
-                result: None,
-            },
-        );
-
-        let v0 = ctx.add_variable(VarDef {
-            name: "V0",
-            bound: vec![],
-        });
-        let v0 = ctx.get_variable(v0);
-        let v1 = ctx.add_variable(VarDef {
-            name: "V1",
-            bound: vec![],
-        });
-        let v1 = ctx.get_variable(v1);
-        let ctx = get_inference_context(ctx);
-
-        assert_eq!(
-            resolve_call(
-                &ctx,
-                Some(ParametricType(LIST_TYPE, vec![v0.clone()]).into()),
-                "head",
-                &[]
-            ),
-            Ok(Some(v0.clone()))
-        );
-        assert_eq!(
-            resolve_call(
-                &ctx,
-                Some(ParametricType(LIST_TYPE, vec![v0.clone()]).into()),
-                "append",
-                &[v0.clone()]
-            ),
-            Ok(None)
-        );
-        assert_eq!(
-            resolve_call(
-                &ctx,
-                Some(ParametricType(LIST_TYPE, vec![v0]).into()),
-                "append",
-                &[v1]
-            ),
-            Err("different variables".to_string())
-        );
-    }
-
-    #[test]
-    fn test_virtual_class() {
-        let mut ctx = basic_ctx();
-
-        let foo = ctx.add_class(ClassDef {
-            base: TypeDef {
-                name: "Foo",
-                methods: HashMap::new(),
-                fields: HashMap::new(),
-            },
-            parents: vec![],
-        });
-
-        let foo1 = ctx.add_class(ClassDef {
-            base: TypeDef {
-                name: "Foo1",
-                methods: HashMap::new(),
-                fields: HashMap::new(),
-            },
-            parents: vec![foo],
-        });
-
-        let foo2 = ctx.add_class(ClassDef {
-            base: TypeDef {
-                name: "Foo2",
-                methods: HashMap::new(),
-                fields: HashMap::new(),
-            },
-            parents: vec![foo1],
-        });
-
-        let bar = ctx.add_class(ClassDef {
-            base: TypeDef {
-                name: "bar",
-                methods: HashMap::new(),
-                fields: HashMap::new(),
-            },
-            parents: vec![],
-        });
-
-        ctx.add_fn(
-            "foo",
-            FnDef {
-                args: vec![VirtualClassType(foo).into()],
-                result: None,
-            },
-        );
-        ctx.add_fn(
-            "foo1",
-            FnDef {
-                args: vec![VirtualClassType(foo1).into()],
-                result: None,
-            },
-        );
-        let ctx = get_inference_context(ctx);
-
-        assert_eq!(
-            resolve_call(&ctx, None, "foo", &[ClassType(foo).into()]),
-            Ok(None)
-        );
-
-        assert_eq!(
-            resolve_call(&ctx, None, "foo", &[ClassType(foo1).into()]),
-            Ok(None)
-        );
-
-        assert_eq!(
-            resolve_call(&ctx, None, "foo", &[ClassType(foo2).into()]),
-            Ok(None)
-        );
-
-        assert_eq!(
-            resolve_call(&ctx, None, "foo", &[ClassType(bar).into()]),
-            Err("not subtype".to_string())
-        );
-
-        assert_eq!(
-            resolve_call(&ctx, None, "foo1", &[ClassType(foo1).into()]),
-            Ok(None)
-        );
-
-        assert_eq!(
-            resolve_call(&ctx, None, "foo1", &[ClassType(foo2).into()]),
-            Ok(None)
-        );
-
-        assert_eq!(
-            resolve_call(&ctx, None, "foo1", &[ClassType(foo).into()]),
-            Err("not subtype".to_string())
-        );
-
-        // virtual class substitution
-        assert_eq!(
-            resolve_call(&ctx, None, "foo", &[VirtualClassType(foo).into()]),
-            Ok(None)
-        );
-        assert_eq!(
-            resolve_call(&ctx, None, "foo", &[VirtualClassType(foo1).into()]),
-            Ok(None)
-        );
-        assert_eq!(
-            resolve_call(&ctx, None, "foo", &[VirtualClassType(foo2).into()]),
-            Ok(None)
-        );
-        assert_eq!(
-            resolve_call(&ctx, None, "foo", &[VirtualClassType(bar).into()]),
-            Err("not subtype".to_string())
-        );
-    }
-}

nac3core/src/lib.rs

@@ -1,593 +1,8 @@
 #![warn(clippy::all)]
-#![allow(clippy::clone_double_ref)]
+#![allow(dead_code)]
 
-extern crate num_bigint;
-extern crate inkwell;
-extern crate rustpython_parser;
-
-pub mod expression_inference;
-pub mod inference_core;
-mod magic_methods;
-pub mod primitives;
-pub mod typedef;
-pub mod context;
-
-use std::error::Error;
-use std::fmt;
-use std::path::Path;
-use std::collections::HashMap;
-
-use num_traits::cast::ToPrimitive;
-
-use rustpython_parser::ast;
-
-use inkwell::OptimizationLevel;
-use inkwell::builder::Builder;
-use inkwell::context::Context;
-use inkwell::module::Module;
-use inkwell::targets::*;
-use inkwell::types;
-use inkwell::types::BasicType;
-use inkwell::values;
-use inkwell::{IntPredicate, FloatPredicate};
-use inkwell::basic_block;
-use inkwell::passes;
-
-
-#[derive(Debug)]
-enum CompileErrorKind {
-    Unsupported(&'static str),
-    MissingTypeAnnotation,
-    UnknownTypeAnnotation,
-    IncompatibleTypes,
-    UnboundIdentifier,
-    BreakOutsideLoop,
-    Internal(&'static str)
-}
-
-impl fmt::Display for CompileErrorKind {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        match self {
-            CompileErrorKind::Unsupported(feature)
-                => write!(f, "The following Python feature is not supported by NAC3: {}", feature),
-            CompileErrorKind::MissingTypeAnnotation
-                => write!(f, "Missing type annotation"),
-            CompileErrorKind::UnknownTypeAnnotation
-                => write!(f, "Unknown type annotation"),
-            CompileErrorKind::IncompatibleTypes
-                => write!(f, "Incompatible types"),
-            CompileErrorKind::UnboundIdentifier
-                => write!(f, "Unbound identifier"),
-            CompileErrorKind::BreakOutsideLoop
-                => write!(f, "Break outside loop"),
-            CompileErrorKind::Internal(details)
-                => write!(f, "Internal compiler error: {}", details),
-        }
-    }
-}
-
-#[derive(Debug)]
-pub struct CompileError {
-    location: ast::Location,
-    kind: CompileErrorKind,
-}
-
-impl fmt::Display for CompileError {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        write!(f, "{}, at {}", self.kind, self.location)
-    }
-}
-
-impl Error for CompileError {}
-
-type CompileResult<T> = Result<T, CompileError>;
-
-pub struct CodeGen<'ctx> {
-    context: &'ctx Context,
-    module: Module<'ctx>,
-    pass_manager: passes::PassManager<values::FunctionValue<'ctx>>,
-    builder: Builder<'ctx>,
-    current_source_location: ast::Location,
-    namespace: HashMap<String, values::PointerValue<'ctx>>,
-    break_bb: Option<basic_block::BasicBlock<'ctx>>,
-}
-
-impl<'ctx> CodeGen<'ctx> {
-    pub fn new(context: &'ctx Context) -> CodeGen<'ctx> {
-        let module = context.create_module("kernel");
-
-        let pass_manager = passes::PassManager::create(&module);
-        pass_manager.add_instruction_combining_pass();
-        pass_manager.add_reassociate_pass();
-        pass_manager.add_gvn_pass();
-        pass_manager.add_cfg_simplification_pass();
-        pass_manager.add_basic_alias_analysis_pass();
-        pass_manager.add_promote_memory_to_register_pass();
-        pass_manager.add_instruction_combining_pass();
-        pass_manager.add_reassociate_pass();
-        pass_manager.initialize();
-
-        let i32_type = context.i32_type();
-        let fn_type = i32_type.fn_type(&[i32_type.into()], false);
-        module.add_function("output", fn_type, None);
-
-        CodeGen {
-            context, module, pass_manager,
-            builder: context.create_builder(),
-            current_source_location: ast::Location::default(),
-            namespace: HashMap::new(),
-            break_bb: None,
-        }
-    }
-
-    fn set_source_location(&mut self, location: ast::Location) {
-        self.current_source_location = location;
-    }
-
-    fn compile_error(&self, kind: CompileErrorKind) -> CompileError {
-        CompileError {
-            location: self.current_source_location,
-            kind
-        }
-    }
-
-    fn get_basic_type(&self, name: &str) -> CompileResult<types::BasicTypeEnum<'ctx>> {
-        match name {
-            "bool" => Ok(self.context.bool_type().into()),
-            "int32" => Ok(self.context.i32_type().into()),
-            "int64" => Ok(self.context.i64_type().into()),
-            "float32" => Ok(self.context.f32_type().into()),
-            "float64" => Ok(self.context.f64_type().into()),
-            _ => Err(self.compile_error(CompileErrorKind::UnknownTypeAnnotation))
-        }
-    }
-
-    fn compile_function_def(
-        &mut self,
-        name: &str,
-        args: &ast::Parameters,
-        body: &ast::Suite,
-        decorator_list: &[ast::Expression],
-        returns: &Option<ast::Expression>,
-        is_async: bool,
-    ) -> CompileResult<values::FunctionValue<'ctx>> {
-        if is_async {
-            return Err(self.compile_error(CompileErrorKind::Unsupported("async functions")))
-        }
-        for decorator in decorator_list.iter() {
-            self.set_source_location(decorator.location);
-            if let ast::ExpressionType::Identifier { name } = &decorator.node {
-                if name != "kernel" && name != "portable" {
-                    return Err(self.compile_error(CompileErrorKind::Unsupported("custom decorators")))
-                }
-            } else {
-                return Err(self.compile_error(CompileErrorKind::Unsupported("decorator must be an identifier")))
-            }
-        }
-
-        let args_type = args.args.iter().map(|val| {
-            self.set_source_location(val.location);
-            if let Some(annotation) = &val.annotation {
-                if let ast::ExpressionType::Identifier { name } = &annotation.node {
-                    Ok(self.get_basic_type(&name)?)
-                } else {
-                    Err(self.compile_error(CompileErrorKind::Unsupported("type annotation must be an identifier")))
-                }
-            } else {
-                Err(self.compile_error(CompileErrorKind::MissingTypeAnnotation))
-            }
-        }).collect::<CompileResult<Vec<types::BasicTypeEnum>>>()?;
-        let return_type = if let Some(returns) = returns {
-            self.set_source_location(returns.location);
-            if let ast::ExpressionType::Identifier { name } = &returns.node {
-                if name == "None" { None } else { Some(self.get_basic_type(name)?) }
-            } else {
-                return Err(self.compile_error(CompileErrorKind::Unsupported("type annotation must be an identifier")))
-            }
-        } else {
-            None
-        };
-
-        let fn_type = match return_type {
-            Some(ty) => ty.fn_type(&args_type, false),
-            None => self.context.void_type().fn_type(&args_type, false)
-        };
-
-        let function = self.module.add_function(name, fn_type, None);
-        let basic_block = self.context.append_basic_block(function, "entry");
-        self.builder.position_at_end(basic_block);
-
-        for (n, arg) in args.args.iter().enumerate() {
-            let param = function.get_nth_param(n as u32).unwrap();
-            let alloca = self.builder.build_alloca(param.get_type(), &arg.arg);
-            self.builder.build_store(alloca, param);
-            self.namespace.insert(arg.arg.clone(), alloca);
-        }
-
-        self.compile_suite(body, return_type)?;
-
-        Ok(function)
-    }
-
-    fn compile_expression(
-        &mut self,
-        expression: &ast::Expression
-    ) -> CompileResult<values::BasicValueEnum<'ctx>> {
-        self.set_source_location(expression.location);
-
-        match &expression.node {
-            ast::ExpressionType::True => Ok(self.context.bool_type().const_int(1, false).into()),
-            ast::ExpressionType::False => Ok(self.context.bool_type().const_int(0, false).into()),
-            ast::ExpressionType::Number { value: ast::Number::Integer { value } } => {
-                let mut bits = value.bits();
-                if value.sign() == num_bigint::Sign::Minus {
-                    bits += 1;
-                }
-                match bits {
-                     0..=32 => Ok(self.context.i32_type().const_int(value.to_i32().unwrap() as _, true).into()),
-                    33..=64 => Ok(self.context.i64_type().const_int(value.to_i64().unwrap() as _, true).into()),
-                          _ => Err(self.compile_error(CompileErrorKind::Unsupported("integers larger than 64 bits")))
-                }
-            },
-            ast::ExpressionType::Number { value: ast::Number::Float { value } } => {
-                Ok(self.context.f64_type().const_float(*value).into())
-            },
-            ast::ExpressionType::Identifier { name } => {
-                match self.namespace.get(name) {
-                    Some(value) => Ok(self.builder.build_load(*value, name).into()),
-                    None => Err(self.compile_error(CompileErrorKind::UnboundIdentifier))
-                }
-            },
-            ast::ExpressionType::Unop { op, a } => {
-                let a = self.compile_expression(&a)?;
-                match (op, a) {
-                    (ast::UnaryOperator::Pos, values::BasicValueEnum::IntValue(a))
-                        => Ok(a.into()),
-                    (ast::UnaryOperator::Pos, values::BasicValueEnum::FloatValue(a))
-                        => Ok(a.into()),
-                    (ast::UnaryOperator::Neg, values::BasicValueEnum::IntValue(a))
-                        => Ok(self.builder.build_int_neg(a, "tmpneg").into()),
-                    (ast::UnaryOperator::Neg, values::BasicValueEnum::FloatValue(a))
-                        => Ok(self.builder.build_float_neg(a, "tmpneg").into()),
-                    (ast::UnaryOperator::Inv, values::BasicValueEnum::IntValue(a))
-                        => Ok(self.builder.build_not(a, "tmpnot").into()),
-                    (ast::UnaryOperator::Not, values::BasicValueEnum::IntValue(a)) => {
-                        // boolean "not"
-                        if a.get_type().get_bit_width() != 1 {
-                            Err(self.compile_error(CompileErrorKind::Unsupported("unimplemented unary operation")))
-                        } else {
-                            Ok(self.builder.build_not(a, "tmpnot").into())
-                        }
-                    },
-                    _ => Err(self.compile_error(CompileErrorKind::Unsupported("unimplemented unary operation"))),
-                }
-            },
-            ast::ExpressionType::Binop { a, op, b } => {
-                let a = self.compile_expression(&a)?;
-                let b = self.compile_expression(&b)?;
-                if a.get_type() != b.get_type() {
-                    return Err(self.compile_error(CompileErrorKind::IncompatibleTypes));
-                }
-                use ast::Operator::*;
-                match (op, a, b) {
-                    (Add, values::BasicValueEnum::IntValue(a), values::BasicValueEnum::IntValue(b))
-                        => Ok(self.builder.build_int_add(a, b, "tmpadd").into()),
-                    (Sub, values::BasicValueEnum::IntValue(a), values::BasicValueEnum::IntValue(b))
-                        => Ok(self.builder.build_int_sub(a, b, "tmpsub").into()),
-                    (Mult, values::BasicValueEnum::IntValue(a), values::BasicValueEnum::IntValue(b))
-                        => Ok(self.builder.build_int_mul(a, b, "tmpmul").into()),
-
-                    (Add, values::BasicValueEnum::FloatValue(a), values::BasicValueEnum::FloatValue(b))
-                        => Ok(self.builder.build_float_add(a, b, "tmpadd").into()),
-                    (Sub, values::BasicValueEnum::FloatValue(a), values::BasicValueEnum::FloatValue(b))
-                        => Ok(self.builder.build_float_sub(a, b, "tmpsub").into()),
-                    (Mult, values::BasicValueEnum::FloatValue(a), values::BasicValueEnum::FloatValue(b))
-                        => Ok(self.builder.build_float_mul(a, b, "tmpmul").into()),
-
-                    (Div, values::BasicValueEnum::FloatValue(a), values::BasicValueEnum::FloatValue(b))
-                        => Ok(self.builder.build_float_div(a, b, "tmpdiv").into()),
-                    (FloorDiv, values::BasicValueEnum::IntValue(a), values::BasicValueEnum::IntValue(b))
-                        => Ok(self.builder.build_int_signed_div(a, b, "tmpdiv").into()),
-                    _ => Err(self.compile_error(CompileErrorKind::Unsupported("unimplemented binary operation"))),
-                }
-            },
-            ast::ExpressionType::Compare { vals, ops } => {
-                let mut vals = vals.iter();
-                let mut ops = ops.iter();
-
-                let mut result = None;
-                let mut a = self.compile_expression(vals.next().unwrap())?;
-                loop {
-                    if let Some(op) = ops.next() {
-                        let b = self.compile_expression(vals.next().unwrap())?;
-                        if a.get_type() != b.get_type() {
-                            return Err(self.compile_error(CompileErrorKind::IncompatibleTypes));
-                        }
-                        let this_result = match (a, b) {
-                            (values::BasicValueEnum::IntValue(a), values::BasicValueEnum::IntValue(b)) => {
-                                match op {
-                                    ast::Comparison::Equal
-                                        => self.builder.build_int_compare(IntPredicate::EQ, a, b, "tmpeq"),
-                                    ast::Comparison::NotEqual
-                                        => self.builder.build_int_compare(IntPredicate::NE, a, b, "tmpne"),
-                                    ast::Comparison::Less
-                                        => self.builder.build_int_compare(IntPredicate::SLT, a, b, "tmpslt"),
-                                    ast::Comparison::LessOrEqual
-                                        => self.builder.build_int_compare(IntPredicate::SLE, a, b, "tmpsle"),
-                                    ast::Comparison::Greater
-                                        => self.builder.build_int_compare(IntPredicate::SGT, a, b, "tmpsgt"),
-                                    ast::Comparison::GreaterOrEqual
-                                        => self.builder.build_int_compare(IntPredicate::SGE, a, b, "tmpsge"),
-                                    _ => return Err(self.compile_error(CompileErrorKind::Unsupported("special comparison"))),
-                                }
-                            },
-                            (values::BasicValueEnum::FloatValue(a), values::BasicValueEnum::FloatValue(b)) => {
-                                match op {
-                                    ast::Comparison::Equal
-                                        => self.builder.build_float_compare(FloatPredicate::OEQ, a, b, "tmpoeq"),
-                                    ast::Comparison::NotEqual
-                                        => self.builder.build_float_compare(FloatPredicate::UNE, a, b, "tmpune"),
-                                    ast::Comparison::Less
-                                        => self.builder.build_float_compare(FloatPredicate::OLT, a, b, "tmpolt"),
-                                    ast::Comparison::LessOrEqual
-                                        => self.builder.build_float_compare(FloatPredicate::OLE, a, b, "tmpole"),
-                                    ast::Comparison::Greater
-                                        => self.builder.build_float_compare(FloatPredicate::OGT, a, b, "tmpogt"),
-                                    ast::Comparison::GreaterOrEqual
-                                        => self.builder.build_float_compare(FloatPredicate::OGE, a, b, "tmpoge"),
-                                    _ => return Err(self.compile_error(CompileErrorKind::Unsupported("special comparison"))),
-                                }
-                            },
-                            _ => return Err(self.compile_error(CompileErrorKind::Unsupported("comparison of non-numerical types"))),
-                        };
-                        match result {
-                            Some(last) => {
-                                result = Some(self.builder.build_and(last, this_result, "tmpand"));
-                            }
-                            None => {
-                                result = Some(this_result);
-                            }
-                        }
-                        a = b;
-                    } else {
-                        return Ok(result.unwrap().into())
-                    }
-                }
-            },
-            ast::ExpressionType::Call { function, args, keywords } => {
-                if !keywords.is_empty() {
-                    return Err(self.compile_error(CompileErrorKind::Unsupported("keyword arguments")))
-                }
-                let args = args.iter().map(|val| self.compile_expression(val))
-                    .collect::<CompileResult<Vec<values::BasicValueEnum>>>()?;
-                self.set_source_location(expression.location);
-                if let ast::ExpressionType::Identifier { name } = &function.node {
-                    match (name.as_str(), args[0]) {
-                        ("int32", values::BasicValueEnum::IntValue(a)) => {
-                            let nbits = a.get_type().get_bit_width();
-                            if nbits < 32 {
-                                Ok(self.builder.build_int_s_extend(a, self.context.i32_type(), "tmpsext").into())
-                            } else if nbits > 32 {
-                                Ok(self.builder.build_int_truncate(a, self.context.i32_type(), "tmptrunc").into())
-                            } else {
-                                Ok(a.into())
-                            }
-                        },
-                        ("int64", values::BasicValueEnum::IntValue(a)) => {
-                            let nbits = a.get_type().get_bit_width();
-                            if nbits < 64 {
-                                Ok(self.builder.build_int_s_extend(a, self.context.i64_type(), "tmpsext").into())
-                            } else {
-                                Ok(a.into())
-                            }
-                        },
-                        ("int32", values::BasicValueEnum::FloatValue(a)) => {
-                            Ok(self.builder.build_float_to_signed_int(a, self.context.i32_type(), "tmpfptosi").into())
-                        },
-                        ("int64", values::BasicValueEnum::FloatValue(a)) => {
-                            Ok(self.builder.build_float_to_signed_int(a, self.context.i64_type(), "tmpfptosi").into())
-                        },
-                        ("float32", values::BasicValueEnum::IntValue(a)) => {
-                            Ok(self.builder.build_signed_int_to_float(a, self.context.f32_type(), "tmpsitofp").into())
-                        },
-                        ("float64", values::BasicValueEnum::IntValue(a)) => {
-                            Ok(self.builder.build_signed_int_to_float(a, self.context.f64_type(), "tmpsitofp").into())
-                        },
-                        ("float32", values::BasicValueEnum::FloatValue(a)) => {
-                            if a.get_type() == self.context.f64_type() {
-                                Ok(self.builder.build_float_trunc(a, self.context.f32_type(), "tmptrunc").into())
-                            } else {
-                                Ok(a.into())
-                            }
-                        },
-                        ("float64", values::BasicValueEnum::FloatValue(a)) => {
-                            if a.get_type() == self.context.f32_type() {
-                                Ok(self.builder.build_float_ext(a, self.context.f64_type(), "tmpext").into())
-                            } else {
-                                Ok(a.into())
-                            }
-                        },
-
-                        ("output", values::BasicValueEnum::IntValue(a)) => {
-                            let fn_value = self.module.get_function("output").unwrap();
-                            Ok(self.builder.build_call(fn_value, &[a.into()], "call")
-                                .try_as_basic_value().left().unwrap())
-                        },
-                        _ => Err(self.compile_error(CompileErrorKind::Unsupported("unrecognized call")))
-                    }
-                } else {
-                    return Err(self.compile_error(CompileErrorKind::Unsupported("function must be an identifier")))
-                }
-            },
-            _ => return Err(self.compile_error(CompileErrorKind::Unsupported("unimplemented expression"))),
-        }
-    }
-
-    fn compile_statement(
-        &mut self,
-        statement: &ast::Statement,
-        return_type: Option<types::BasicTypeEnum>
-    ) -> CompileResult<()> {
-        self.set_source_location(statement.location);
-
-        use ast::StatementType::*;
-        match &statement.node {
-            Assign { targets, value } => {
-                let value = self.compile_expression(value)?;
-                for target in targets.iter() {
-                    self.set_source_location(target.location);
-                    if let ast::ExpressionType::Identifier { name } = &target.node {
-                        let builder = &self.builder;
-                        let target = self.namespace.entry(name.clone()).or_insert_with(
-                            || builder.build_alloca(value.get_type(), name));
-                        if target.get_type() != value.get_type().ptr_type(inkwell::AddressSpace::Generic) {
-                            return Err(self.compile_error(CompileErrorKind::IncompatibleTypes));
-                        }
-                        builder.build_store(*target, value);
-                    } else {
-                        return Err(self.compile_error(CompileErrorKind::Unsupported("assignment target must be an identifier")))
-                    }
-                }
-            },
-            Expression { expression } => { self.compile_expression(expression)?; },
-            If { test, body, orelse } => {
-                let test = self.compile_expression(test)?;
-                if test.get_type() != self.context.bool_type().into() {
-                    return Err(self.compile_error(CompileErrorKind::IncompatibleTypes));
-                }
-
-                let parent = self.builder.get_insert_block().unwrap().get_parent().unwrap();
-                let then_bb = self.context.append_basic_block(parent, "then");
-                let else_bb = self.context.append_basic_block(parent, "else");
-                let cont_bb = self.context.append_basic_block(parent, "ifcont");
-                self.builder.build_conditional_branch(test.into_int_value(), then_bb, else_bb);
-
-                self.builder.position_at_end(then_bb);
-                self.compile_suite(body, return_type)?;
-                self.builder.build_unconditional_branch(cont_bb);
-
-                self.builder.position_at_end(else_bb);
-                if let Some(orelse) = orelse {
-                    self.compile_suite(orelse, return_type)?;
-                }
-                self.builder.build_unconditional_branch(cont_bb);
-                self.builder.position_at_end(cont_bb);
-            },
-            While { test, body, orelse } => {
-                let parent = self.builder.get_insert_block().unwrap().get_parent().unwrap();
-                let test_bb = self.context.append_basic_block(parent, "test");
-                self.builder.build_unconditional_branch(test_bb);
-                self.builder.position_at_end(test_bb);
-                let test = self.compile_expression(test)?;
-                if test.get_type() != self.context.bool_type().into() {
-                    return Err(self.compile_error(CompileErrorKind::IncompatibleTypes));
-                }
-
-                let then_bb = self.context.append_basic_block(parent, "then");
-                let else_bb = self.context.append_basic_block(parent, "else");
-                let cont_bb = self.context.append_basic_block(parent, "ifcont");
-                self.builder.build_conditional_branch(test.into_int_value(), then_bb, else_bb);
-
-                self.break_bb = Some(cont_bb);
-
-                self.builder.position_at_end(then_bb);
-                self.compile_suite(body, return_type)?;
-                self.builder.build_unconditional_branch(test_bb);
-
-                self.builder.position_at_end(else_bb);
-                if let Some(orelse) = orelse {
-                    self.compile_suite(orelse, return_type)?;
-                }
-                self.builder.build_unconditional_branch(cont_bb);
-                self.builder.position_at_end(cont_bb);
-
-                self.break_bb = None;
-            },
-            Break => {
-                if let Some(bb) = self.break_bb {
-                    self.builder.build_unconditional_branch(bb);
-                    let parent = self.builder.get_insert_block().unwrap().get_parent().unwrap();
-                    let unreachable_bb = self.context.append_basic_block(parent, "unreachable");
-                    self.builder.position_at_end(unreachable_bb);
-                } else {
-                    return Err(self.compile_error(CompileErrorKind::BreakOutsideLoop));
-                }
-            }
-            Return { value: Some(value) } => {
-                if let Some(return_type) = return_type {
-                    let value = self.compile_expression(value)?;
-                    if value.get_type() != return_type {
-                        return Err(self.compile_error(CompileErrorKind::IncompatibleTypes));
-                    }
-                    self.builder.build_return(Some(&value));
-                } else {
-                    return Err(self.compile_error(CompileErrorKind::IncompatibleTypes));
-                }
-            },
-            Return { value: None } => {
-                if !return_type.is_none() {
-                    return Err(self.compile_error(CompileErrorKind::IncompatibleTypes));
-                }
-                self.builder.build_return(None);
-            },
-            Pass => (),
-            _ => return Err(self.compile_error(CompileErrorKind::Unsupported("special statement"))),
-        }
-        Ok(())
-    }
-
-    fn compile_suite(
-        &mut self,
-        suite: &ast::Suite,
-        return_type: Option<types::BasicTypeEnum>
-    ) -> CompileResult<()> {
-        for statement in suite.iter() {
-            self.compile_statement(statement, return_type)?;
-        }
-        Ok(())
-    }
-
-    pub fn compile_toplevel(&mut self, statement: &ast::Statement) -> CompileResult<()> {
-        self.set_source_location(statement.location);
-        if let ast::StatementType::FunctionDef {
-                    is_async,
-                    name,
-                    args,
-                    body,
-                    decorator_list,
-                    returns,
-                } = &statement.node {
-            let function = self.compile_function_def(name, args, body, decorator_list, returns, *is_async)?;
-            self.pass_manager.run_on(&function);
-            Ok(())
-        } else {
-            Err(self.compile_error(CompileErrorKind::Internal("top-level is not a function definition")))
-        }
-    }
-
-    pub fn print_ir(&self) {
-        self.module.print_to_stderr();
-    }
-
-    pub fn output(&self, filename: &str) {
-        //let triple = TargetTriple::create("riscv32-none-linux-gnu");
-        let triple = TargetMachine::get_default_triple();
-        let target = Target::from_triple(&triple)
-            .expect("couldn't create target from target triple");
-
-        let target_machine = target
-            .create_target_machine(
-                &triple,
-                "",
-                "",
-                OptimizationLevel::Default,
-                RelocMode::Default,
-                CodeModel::Default,
-            )
-            .expect("couldn't create target machine");
-
-        target_machine
-            .write_to_file(&self.module, FileType::Object, Path::new(filename))
-            .expect("couldn't write module to file");
-    }
-}
+mod codegen;
+mod location;
+mod symbol_resolver;
+mod top_level;
+mod typecheck;

nac3core/src/location.rs

@@ -0,0 +1,31 @@
+use rustpython_parser::ast;
+use std::vec::Vec;
+
+#[derive(Clone, Copy, PartialEq)]
+pub struct FileID(u32);
+
+#[derive(Clone, Copy, PartialEq)]
+pub enum Location {
+    CodeRange(FileID, ast::Location),
+    Builtin,
+}
+
+pub struct FileRegistry {
+    files: Vec<String>,
+}
+
+impl FileRegistry {
+    pub fn new() -> FileRegistry {
+        FileRegistry { files: Vec::new() }
+    }
+
+    pub fn add_file(&mut self, path: &str) -> FileID {
+        let index = self.files.len() as u32;
+        self.files.push(path.to_owned());
+        FileID(index)
+    }
+
+    pub fn query_file(&self, id: FileID) -> &str {
+        &self.files[id.0 as usize]
+    }
+}

nac3core/src/magic_methods.rs

@@ -1,58 +0,0 @@
-use rustpython_parser::ast::{Comparison, Operator, UnaryOperator};
-
-pub fn binop_name(op: &Operator) -> &'static str {
-    match op {
-        Operator::Add => "__add__",
-        Operator::Sub => "__sub__",
-        Operator::Div => "__truediv__",
-        Operator::Mod => "__mod__",
-        Operator::Mult => "__mul__",
-        Operator::Pow => "__pow__",
-        Operator::BitOr => "__or__",
-        Operator::BitXor => "__xor__",
-        Operator::BitAnd => "__and__",
-        Operator::LShift => "__lshift__",
-        Operator::RShift => "__rshift__",
-        Operator::FloorDiv => "__floordiv__",
-        Operator::MatMult => "__matmul__",
-    }
-}
-
-pub fn binop_assign_name(op: &Operator) -> &'static str {
-    match op {
-        Operator::Add => "__iadd__",
-        Operator::Sub => "__isub__",
-        Operator::Div => "__itruediv__",
-        Operator::Mod => "__imod__",
-        Operator::Mult => "__imul__",
-        Operator::Pow => "__ipow__",
-        Operator::BitOr => "__ior__",
-        Operator::BitXor => "__ixor__",
-        Operator::BitAnd => "__iand__",
-        Operator::LShift => "__ilshift__",
-        Operator::RShift => "__irshift__",
-        Operator::FloorDiv => "__ifloordiv__",
-        Operator::MatMult => "__imatmul__",
-    }
-}
-
-pub fn unaryop_name(op: &UnaryOperator) -> &'static str {
-    match op {
-        UnaryOperator::Pos => "__pos__",
-        UnaryOperator::Neg => "__neg__",
-        UnaryOperator::Not => "__not__",
-        UnaryOperator::Inv => "__inv__",
-    }
-}
-
-pub fn comparison_name(op: &Comparison) -> Option<&'static str> {
-    match op {
-        Comparison::Less => Some("__lt__"),
-        Comparison::LessOrEqual => Some("__le__"),
-        Comparison::Greater => Some("__gt__"),
-        Comparison::GreaterOrEqual => Some("__ge__"),
-        Comparison::Equal => Some("__eq__"),
-        Comparison::NotEqual => Some("__ne__"),
-        _ => None,
-    }
-}

nac3core/src/primitives.rs

@@ -1,184 +0,0 @@
-use super::typedef::{TypeEnum::*, *};
-use crate::context::*;
-use std::collections::HashMap;
-
-pub const TUPLE_TYPE: ParamId = ParamId(0);
-pub const LIST_TYPE: ParamId = ParamId(1);
-
-pub const BOOL_TYPE: PrimitiveId = PrimitiveId(0);
-pub const INT32_TYPE: PrimitiveId = PrimitiveId(1);
-pub const INT64_TYPE: PrimitiveId = PrimitiveId(2);
-pub const FLOAT_TYPE: PrimitiveId = PrimitiveId(3);
-
-fn impl_math(def: &mut TypeDef, ty: &Type) {
-    let result = Some(ty.clone());
-    let fun = FnDef {
-        args: vec![ty.clone()],
-        result: result.clone(),
-    };
-    def.methods.insert("__add__", fun.clone());
-    def.methods.insert("__sub__", fun.clone());
-    def.methods.insert("__mul__", fun.clone());
-    def.methods.insert(
-        "__neg__",
-        FnDef {
-            args: vec![],
-            result,
-        },
-    );
-    def.methods.insert(
-        "__truediv__",
-        FnDef {
-            args: vec![ty.clone()],
-            result: Some(PrimitiveType(FLOAT_TYPE).into()),
-        },
-    );
-    def.methods.insert("__floordiv__", fun.clone());
-    def.methods.insert("__mod__", fun.clone());
-    def.methods.insert("__pow__", fun);
-}
-
-fn impl_bits(def: &mut TypeDef, ty: &Type) {
-    let result = Some(ty.clone());
-    let fun = FnDef {
-        args: vec![PrimitiveType(INT32_TYPE).into()],
-        result,
-    };
-
-    def.methods.insert("__lshift__", fun.clone());
-    def.methods.insert("__rshift__", fun);
-    def.methods.insert(
-        "__xor__",
-        FnDef {
-            args: vec![ty.clone()],
-            result: Some(ty.clone()),
-        },
-    );
-}
-
-fn impl_eq(def: &mut TypeDef, ty: &Type) {
-    let fun = FnDef {
-        args: vec![ty.clone()],
-        result: Some(PrimitiveType(BOOL_TYPE).into()),
-    };
-
-    def.methods.insert("__eq__", fun.clone());
-    def.methods.insert("__ne__", fun);
-}
-
-fn impl_order(def: &mut TypeDef, ty: &Type) {
-    let fun = FnDef {
-        args: vec![ty.clone()],
-        result: Some(PrimitiveType(BOOL_TYPE).into()),
-    };
-
-    def.methods.insert("__lt__", fun.clone());
-    def.methods.insert("__gt__", fun.clone());
-    def.methods.insert("__le__", fun.clone());
-    def.methods.insert("__ge__", fun);
-}
-
-pub fn basic_ctx() -> TopLevelContext<'static> {
-    let primitives = [
-        TypeDef {
-            name: "bool",
-            fields: HashMap::new(),
-            methods: HashMap::new(),
-        },
-        TypeDef {
-            name: "int32",
-            fields: HashMap::new(),
-            methods: HashMap::new(),
-        },
-        TypeDef {
-            name: "int64",
-            fields: HashMap::new(),
-            methods: HashMap::new(),
-        },
-        TypeDef {
-            name: "float",
-            fields: HashMap::new(),
-            methods: HashMap::new(),
-        },
-    ]
-    .to_vec();
-    let mut ctx = TopLevelContext::new(primitives);
-
-    let b = ctx.get_primitive(BOOL_TYPE);
-    let b_def = ctx.get_primitive_def_mut(BOOL_TYPE);
-    impl_eq(b_def, &b);
-    let int32 = ctx.get_primitive(INT32_TYPE);
-    let int32_def = ctx.get_primitive_def_mut(INT32_TYPE);
-    impl_math(int32_def, &int32);
-    impl_bits(int32_def, &int32);
-    impl_order(int32_def, &int32);
-    impl_eq(int32_def, &int32);
-    let int64 = ctx.get_primitive(INT64_TYPE);
-    let int64_def = ctx.get_primitive_def_mut(INT64_TYPE);
-    impl_math(int64_def, &int64);
-    impl_bits(int64_def, &int64);
-    impl_order(int64_def, &int64);
-    impl_eq(int64_def, &int64);
-    let float = ctx.get_primitive(FLOAT_TYPE);
-    let float_def = ctx.get_primitive_def_mut(FLOAT_TYPE);
-    impl_math(float_def, &float);
-    impl_order(float_def, &float);
-    impl_eq(float_def, &float);
-
-    let t = ctx.add_variable_private(VarDef {
-        name: "T",
-        bound: vec![],
-    });
-
-    ctx.add_parametric(ParametricDef {
-        base: TypeDef {
-            name: "tuple",
-            fields: HashMap::new(),
-            methods: HashMap::new(),
-        },
-        // we have nothing for tuple, so no param def
-        params: vec![],
-    });
-
-    ctx.add_parametric(ParametricDef {
-        base: TypeDef {
-            name: "list",
-            fields: HashMap::new(),
-            methods: HashMap::new(),
-        },
-        params: vec![t],
-    });
-
-    let i = ctx.add_variable_private(VarDef {
-        name: "I",
-        bound: vec![
-            PrimitiveType(INT32_TYPE).into(),
-            PrimitiveType(INT64_TYPE).into(),
-            PrimitiveType(FLOAT_TYPE).into(),
-        ],
-    });
-    let args = vec![TypeVariable(i).into()];
-    ctx.add_fn(
-        "int32",
-        FnDef {
-            args: args.clone(),
-            result: Some(PrimitiveType(INT32_TYPE).into()),
-        },
-    );
-    ctx.add_fn(
-        "int64",
-        FnDef {
-            args: args.clone(),
-            result: Some(PrimitiveType(INT64_TYPE).into()),
-        },
-    );
-    ctx.add_fn(
-        "float",
-        FnDef {
-            args,
-            result: Some(PrimitiveType(FLOAT_TYPE).into()),
-        },
-    );
-
-    ctx
-}

nac3core/src/symbol_resolver.rs

@@ -0,0 +1,174 @@
+use std::cell::RefCell;
+use std::collections::HashMap;
+
+use crate::top_level::{DefinitionId, TopLevelContext, TopLevelDef};
+use crate::typecheck::{
+    type_inferencer::PrimitiveStore,
+    typedef::{Type, Unifier},
+};
+use crate::{location::Location, typecheck::typedef::TypeEnum};
+use itertools::{chain, izip};
+use rustpython_parser::ast::Expr;
+
+#[derive(Clone, PartialEq)]
+pub enum SymbolValue {
+    I32(i32),
+    I64(i64),
+    Double(f64),
+    Bool(bool),
+    Tuple(Vec<SymbolValue>),
+    // we should think about how to implement bytes later...
+    // Bytes(&'a [u8]),
+}
+
+pub trait SymbolResolver {
+    // get type of type variable identifier or top-level function type
+    fn get_symbol_type(
+        &self,
+        unifier: &mut Unifier,
+        primitives: &PrimitiveStore,
+        str: &str,
+    ) -> Option<Type>;
+    // get the top-level definition of identifiers
+    fn get_identifier_def(&self, str: &str) -> Option<DefinitionId>;
+    fn get_symbol_value(&self, str: &str) -> Option<SymbolValue>;
+    fn get_symbol_location(&self, str: &str) -> Option<Location>;
+    // handle function call etc.
+}
+
+// convert type annotation into type
+pub fn parse_type_annotation<T>(
+    resolver: &dyn SymbolResolver,
+    top_level: &TopLevelContext,
+    unifier: &mut Unifier,
+    primitives: &PrimitiveStore,
+    expr: &Expr<T>,
+) -> Result<Type, String> {
+    use rustpython_parser::ast::ExprKind::*;
+    match &expr.node {
+        Name { id, .. } => match id.as_str() {
+            "int32" => Ok(primitives.int32),
+            "int64" => Ok(primitives.int64),
+            "float" => Ok(primitives.float),
+            "bool" => Ok(primitives.bool),
+            "None" => Ok(primitives.none),
+            x => {
+                let obj_id = resolver.get_identifier_def(x);
+                if let Some(obj_id) = obj_id {
+                    let defs = top_level.definitions.read();
+                    let def = defs[obj_id.0].read();
+                    if let TopLevelDef::Class { fields, methods, type_vars, .. } = &*def {
+                        if !type_vars.is_empty() {
+                            return Err(format!(
+                                "Unexpected number of type parameters: expected {} but got 0",
+                                type_vars.len()
+                            ));
+                        }
+                        let fields = RefCell::new(
+                            chain(
+                                fields.iter().map(|(k, v)| (k.clone(), *v)),
+                                methods.iter().map(|(k, v, _)| (k.clone(), *v)),
+                            )
+                            .collect(),
+                        );
+                        Ok(unifier.add_ty(TypeEnum::TObj {
+                            obj_id,
+                            fields,
+                            params: Default::default(),
+                        }))
+                    } else {
+                        Err("Cannot use function name as type".into())
+                    }
+                } else {
+                    // it could be a type variable
+                    let ty = resolver
+                        .get_symbol_type(unifier, primitives, x)
+                        .ok_or_else(|| "Cannot use function name as type".to_owned())?;
+                    if let TypeEnum::TVar { .. } = &*unifier.get_ty(ty) {
+                        Ok(ty)
+                    } else {
+                        Err(format!("Unknown type annotation {}", x))
+                    }
+                }
+            }
+        },
+        Subscript { value, slice, .. } => {
+            if let Name { id, .. } = &value.node {
+                if id == "virtual" {
+                    let ty =
+                        parse_type_annotation(resolver, top_level, unifier, primitives, slice)?;
+                    Ok(unifier.add_ty(TypeEnum::TVirtual { ty }))
+                } else {
+                    let types = if let Tuple { elts, .. } = &slice.node {
+                        elts.iter()
+                            .map(|v| {
+                                parse_type_annotation(resolver, top_level, unifier, primitives, v)
+                            })
+                            .collect::<Result<Vec<_>, _>>()?
+                    } else {
+                        vec![parse_type_annotation(
+                            resolver, top_level, unifier, primitives, slice,
+                        )?]
+                    };
+
+                    let obj_id = resolver
+                        .get_identifier_def(id)
+                        .ok_or_else(|| format!("Unknown type annotation {}", id))?;
+                    let defs = top_level.definitions.read();
+                    let def = defs[obj_id.0].read();
+                    if let TopLevelDef::Class { fields, methods, type_vars, .. } = &*def {
+                        if types.len() != type_vars.len() {
+                            return Err(format!(
+                                "Unexpected number of type parameters: expected {} but got {}",
+                                type_vars.len(),
+                                types.len()
+                            ));
+                        }
+                        let mut subst = HashMap::new();
+                        for (var, ty) in izip!(type_vars.iter(), types.iter()) {
+                            let id = if let TypeEnum::TVar { id, .. } = &*unifier.get_ty(*var) {
+                                *id
+                            } else {
+                                unreachable!()
+                            };
+                            subst.insert(id, *ty);
+                        }
+                        let mut fields = fields
+                            .iter()
+                            .map(|(attr, ty)| {
+                                let ty = unifier.subst(*ty, &subst).unwrap_or(*ty);
+                                (attr.clone(), ty)
+                            })
+                            .collect::<HashMap<_, _>>();
+                        fields.extend(methods.iter().map(|(attr, ty, _)| {
+                            let ty = unifier.subst(*ty, &subst).unwrap_or(*ty);
+                            (attr.clone(), ty)
+                        }));
+                        Ok(unifier.add_ty(TypeEnum::TObj {
+                            obj_id,
+                            fields: fields.into(),
+                            params: subst.into(),
+                        }))
+                    } else {
+                        Err("Cannot use function name as type".into())
+                    }
+                }
+            } else {
+                Err("unsupported type expression".into())
+            }
+        }
+        _ => Err("unsupported type expression".into()),
+    }
+}
+
+impl dyn SymbolResolver + Send + Sync {
+    pub fn parse_type_annotation<T>(
+        &self,
+        top_level: &TopLevelContext,
+        unifier: &mut Unifier,
+        primitives: &PrimitiveStore,
+        expr: &Expr<T>,
+    ) -> Result<Type, String> {
+        parse_type_annotation(self, top_level, unifier, primitives, expr)
+    }
+}

nac3core/src/top_level.rs

@@ -0,0 +1,778 @@
+use std::borrow::BorrowMut;
+use std::ops::{Deref, DerefMut};
+use std::{collections::HashMap, collections::HashSet, sync::Arc};
+
+use super::typecheck::type_inferencer::PrimitiveStore;
+use super::typecheck::typedef::{SharedUnifier, Type, TypeEnum, Unifier};
+use crate::typecheck::typedef::{FunSignature, FuncArg};
+use crate::{symbol_resolver::SymbolResolver, typecheck::typedef::Mapping};
+use itertools::Itertools;
+use parking_lot::{Mutex, RwLock};
+use rustpython_parser::ast::{self, Stmt};
+
+#[derive(PartialEq, Eq, PartialOrd, Ord, Clone, Copy, Hash)]
+pub struct DefinitionId(pub usize);
+
+pub enum TopLevelDef {
+    Class {
+        // object ID used for TypeEnum
+        object_id: DefinitionId,
+        // type variables bounded to the class.
+        type_vars: Vec<Type>,
+        // class fields
+        fields: Vec<(String, Type)>,
+        // class methods, pointing to the corresponding function definition.
+        methods: Vec<(String, Type, DefinitionId)>,
+        // ancestor classes, including itself.
+        ancestors: Vec<DefinitionId>,
+        // symbol resolver of the module defined the class, none if it is built-in type
+        resolver: Option<Arc<Mutex<dyn SymbolResolver + Send + Sync>>>,
+    },
+    Function {
+        // prefix for symbol, should be unique globally, and not ending with numbers
+        name: String,
+        // function signature.
+        signature: Type,
+        /// Function instance to symbol mapping
+        /// Key: string representation of type variable values, sorted by variable ID in ascending
+        /// order, including type variables associated with the class.
+        /// Value: function symbol name.
+        instance_to_symbol: HashMap<String, String>,
+        /// Function instances to annotated AST mapping
+        /// Key: string representation of type variable values, sorted by variable ID in ascending
+        /// order, including type variables associated with the class. Excluding rigid type
+        /// variables.
+        /// Value: AST annotated with types together with a unification table index. Could contain
+        /// rigid type variables that would be substituted when the function is instantiated.
+        instance_to_stmt: HashMap<String, (Stmt<Option<Type>>, usize)>,
+        // symbol resolver of the module defined the class
+        resolver: Option<Arc<Mutex<dyn SymbolResolver + Send + Sync>>>,
+    },
+    Initializer {
+        class_id: DefinitionId,
+    },
+}
+
+impl TopLevelDef {
+    fn get_function_type(&self) -> Result<Type, String> {
+        if let Self::Function { signature, .. } = self {
+            Ok(*signature)
+        } else {
+            Err("only expect function def here".into())
+        }
+    }
+}
+
+pub struct TopLevelContext {
+    pub definitions: Arc<RwLock<Vec<Arc<RwLock<TopLevelDef>>>>>,
+    pub unifiers: Arc<RwLock<Vec<(SharedUnifier, PrimitiveStore)>>>,
+}
+
+pub struct TopLevelComposer {
+    // list of top level definitions, same as top level context
+    pub definition_ast_list: Arc<RwLock<Vec<(Arc<RwLock<TopLevelDef>>, Option<ast::Stmt<()>>)>>>,
+    // start as a primitive unifier, will add more top_level defs inside
+    pub unifier: Unifier,
+    // primitive store
+    pub primitives: PrimitiveStore,
+    // mangled class method name to def_id
+    pub class_method_to_def_id: HashMap<String, DefinitionId>,
+    // record the def id of the classes whoses fields and methods are to be analyzed
+    pub to_be_analyzed_class: Vec<DefinitionId>,
+}
+
+impl TopLevelComposer {
+    pub fn to_top_level_context(&self) -> TopLevelContext {
+        let def_list =
+            self.definition_ast_list.read().iter().map(|(x, _)| x.clone()).collect::<Vec<_>>();
+        TopLevelContext {
+            definitions: RwLock::new(def_list).into(),
+            // FIXME: all the big unifier or?
+            unifiers: Default::default(),
+        }
+    }
+
+    fn name_mangling(mut class_name: String, method_name: &str) -> String {
+        class_name.push_str(method_name);
+        class_name
+    }
+
+    pub fn make_primitives() -> (PrimitiveStore, Unifier) {
+        let mut unifier = Unifier::new();
+        let int32 = unifier.add_ty(TypeEnum::TObj {
+            obj_id: DefinitionId(0),
+            fields: HashMap::new().into(),
+            params: HashMap::new().into(),
+        });
+        let int64 = unifier.add_ty(TypeEnum::TObj {
+            obj_id: DefinitionId(1),
+            fields: HashMap::new().into(),
+            params: HashMap::new().into(),
+        });
+        let float = unifier.add_ty(TypeEnum::TObj {
+            obj_id: DefinitionId(2),
+            fields: HashMap::new().into(),
+            params: HashMap::new().into(),
+        });
+        let bool = unifier.add_ty(TypeEnum::TObj {
+            obj_id: DefinitionId(3),
+            fields: HashMap::new().into(),
+            params: HashMap::new().into(),
+        });
+        let none = unifier.add_ty(TypeEnum::TObj {
+            obj_id: DefinitionId(4),
+            fields: HashMap::new().into(),
+            params: HashMap::new().into(),
+        });
+        let primitives = PrimitiveStore { int32, int64, float, bool, none };
+        crate::typecheck::magic_methods::set_primitives_magic_methods(&primitives, &mut unifier);
+        (primitives, unifier)
+    }
+
+    /// return a composer and things to make a "primitive" symbol resolver, so that the symbol
+    /// resolver can later figure out primitive type definitions when passed a primitive type name
+    pub fn new() -> (Vec<(String, DefinitionId, Type)>, Self) {
+        let primitives = Self::make_primitives();
+
+        let top_level_def_list = vec![
+            Arc::new(RwLock::new(Self::make_top_level_class_def(0, None))),
+            Arc::new(RwLock::new(Self::make_top_level_class_def(1, None))),
+            Arc::new(RwLock::new(Self::make_top_level_class_def(2, None))),
+            Arc::new(RwLock::new(Self::make_top_level_class_def(3, None))),
+            Arc::new(RwLock::new(Self::make_top_level_class_def(4, None))),
+        ];
+
+        let ast_list: Vec<Option<ast::Stmt<()>>> = vec![None, None, None, None, None];
+
+        let composer = TopLevelComposer {
+            definition_ast_list: RwLock::new(
+                top_level_def_list.into_iter().zip(ast_list).collect_vec(),
+            )
+            .into(),
+            primitives: primitives.0,
+            unifier: primitives.1,
+            class_method_to_def_id: Default::default(),
+            to_be_analyzed_class: Default::default(),
+        };
+        (
+            vec![
+                ("int32".into(), DefinitionId(0), composer.primitives.int32),
+                ("int64".into(), DefinitionId(1), composer.primitives.int64),
+                ("float".into(), DefinitionId(2), composer.primitives.float),
+                ("bool".into(), DefinitionId(3), composer.primitives.bool),
+                ("none".into(), DefinitionId(4), composer.primitives.none),
+            ],
+            composer,
+        )
+    }
+
+    /// already include the definition_id of itself inside the ancestors vector
+    /// when first regitering, the type_vars, fields, methods, ancestors are invalid
+    pub fn make_top_level_class_def(
+        index: usize,
+        resolver: Option<Arc<Mutex<dyn SymbolResolver + Send + Sync>>>,
+    ) -> TopLevelDef {
+        TopLevelDef::Class {
+            object_id: DefinitionId(index),
+            type_vars: Default::default(),
+            fields: Default::default(),
+            methods: Default::default(),
+            ancestors: vec![DefinitionId(index)],
+            resolver,
+        }
+    }
+
+    /// when first registering, the type is a invalid value
+    pub fn make_top_level_function_def(
+        name: String,
+        ty: Type,
+        resolver: Option<Arc<Mutex<dyn SymbolResolver + Send + Sync>>>,
+    ) -> TopLevelDef {
+        TopLevelDef::Function {
+            name,
+            signature: ty,
+            instance_to_symbol: Default::default(),
+            instance_to_stmt: Default::default(),
+            resolver,
+        }
+    }
+
+    /// step 0, register, just remeber the names of top level classes/function
+    pub fn register_top_level(
+        &mut self,
+        ast: ast::Stmt<()>,
+        resolver: Option<Arc<Mutex<dyn SymbolResolver + Send + Sync>>>,
+    ) -> Result<(String, DefinitionId), String> {
+        let mut def_list = self.definition_ast_list.write();
+        match &ast.node {
+            ast::StmtKind::ClassDef { name, body, .. } => {
+                let class_name = name.to_string();
+                let class_def_id = def_list.len();
+
+                // add the class to the definition lists
+                // since later when registering class method, ast will still be used,
+                // here push None temporarly, later will move the ast inside
+                let mut class_def_ast = (
+                    Arc::new(RwLock::new(Self::make_top_level_class_def(
+                        class_def_id,
+                        resolver.clone(),
+                    ))),
+                    None,
+                );
+
+                // parse class def body and register class methods into the def list.
+                // module's symbol resolver would not know the name of the class methods,
+                // thus cannot return their definition_id
+                let mut class_method_name_def_ids: Vec<(
+                    String,
+                    Arc<RwLock<TopLevelDef>>,
+                    DefinitionId,
+                )> = Vec::new();
+                let mut class_method_index_offset = 0;
+                for b in body {
+                    if let ast::StmtKind::FunctionDef { name: method_name, .. } = &b.node {
+                        let method_name = Self::name_mangling(class_name.clone(), method_name);
+                        let method_def_id = def_list.len() + {
+                            class_method_index_offset += 1;
+                            class_method_index_offset
+                        };
+
+                        // dummy method define here
+                        // the ast of class method is in the class, push None in to the list here
+                        class_method_name_def_ids.push((
+                            method_name.clone(),
+                            RwLock::new(Self::make_top_level_function_def(
+                                method_name.clone(),
+                                self.primitives.none,
+                                resolver.clone(),
+                            ))
+                            .into(),
+                            DefinitionId(method_def_id),
+                        ));
+                    }
+                }
+                // move the ast to the entry of the class in the ast_list
+                class_def_ast.1 = Some(ast);
+
+                // now class_def_ast and class_method_def_ast_ids are ok, put them into actual def list in correct order
+                def_list.push(class_def_ast);
+                for (name, def, id) in class_method_name_def_ids {
+                    def_list.push((def, None));
+                    self.class_method_to_def_id.insert(name, id);
+                }
+
+                // put the constructor into the def_list
+                def_list.push((
+                    RwLock::new(TopLevelDef::Initializer { class_id: DefinitionId(class_def_id) })
+                        .into(),
+                    None,
+                ));
+
+                // class, put its def_id into the to be analyzed set
+                self.to_be_analyzed_class.push(DefinitionId(class_def_id));
+
+                Ok((class_name, DefinitionId(class_def_id)))
+            }
+
+            ast::StmtKind::FunctionDef { name, .. } => {
+                let fun_name = name.to_string();
+
+                // add to the definition list
+                def_list.push((
+                    RwLock::new(Self::make_top_level_function_def(
+                        name.into(),
+                        self.primitives.none,
+                        resolver,
+                    ))
+                    .into(),
+                    Some(ast),
+                ));
+
+                // return
+                Ok((fun_name, DefinitionId(def_list.len() - 1)))
+            }
+
+            _ => Err("only registrations of top level classes/functions are supprted".into()),
+        }
+    }
+
+    /// step 1, analyze the type vars associated with top level class
+    fn analyze_top_level_class_type_var(&mut self) -> Result<(), String> {
+        let mut def_list = self.definition_ast_list.write();
+        let converted_top_level = &self.to_top_level_context();
+        let primitives = &self.primitives;
+        let unifier = &mut self.unifier;
+
+        for (class_def, class_ast) in def_list.iter_mut() {
+            // only deal with class def here
+            let mut class_def = class_def.write();
+            let (class_bases_ast, class_def_type_vars, class_resolver) = {
+                if let TopLevelDef::Class { type_vars, resolver, .. } = class_def.deref_mut() {
+                    if let Some(ast::Located {
+                        node: ast::StmtKind::ClassDef { bases, .. }, ..
+                    }) = class_ast
+                    {
+                        (bases, type_vars, resolver)
+                    } else {
+                        unreachable!("must be both class")
+                    }
+                } else {
+                    continue;
+                }
+            };
+            let class_resolver = class_resolver.as_ref().unwrap().lock();
+
+            let mut is_generic = false;
+            for b in class_bases_ast {
+                match &b.node {
+                    // analyze typevars bounded to the class,
+                    // only support things like `class A(Generic[T, V])`,
+                    // things like `class A(Generic[T, V, ImportedModule.T])` is not supported
+                    // i.e. only simple names are allowed in the subscript
+                    // should update the TopLevelDef::Class.typevars and the TypeEnum::TObj.params
+                    ast::ExprKind::Subscript { value, slice, .. } if matches!(&value.node, ast::ExprKind::Name { id, .. } if id == "Generic") =>
+                    {
+                        if !is_generic {
+                            is_generic = true;
+                        } else {
+                            return Err("Only single Generic[...] can be in bases".into());
+                        }
+
+                        // if `class A(Generic[T, V, G])`
+                        if let ast::ExprKind::Tuple { elts, .. } = &slice.node {
+                            // parse the type vars
+                            let type_vars = elts
+                                .iter()
+                                .map(|e| {
+                                    class_resolver.parse_type_annotation(
+                                        converted_top_level,
+                                        unifier.borrow_mut(),
+                                        primitives,
+                                        e,
+                                    )
+                                })
+                                .collect::<Result<Vec<_>, _>>()?;
+
+                            // check if all are unique type vars
+                            let mut occured_type_var_id: HashSet<u32> = HashSet::new();
+                            let all_unique_type_var = type_vars.iter().all(|x| {
+                                let ty = unifier.get_ty(*x);
+                                if let TypeEnum::TVar { id, .. } = ty.as_ref() {
+                                    occured_type_var_id.insert(*id)
+                                } else {
+                                    false
+                                }
+                            });
+
+                            if !all_unique_type_var {
+                                return Err("expect unique type variables".into());
+                            }
+
+                            // add to TopLevelDef
+                            class_def_type_vars.extend(type_vars);
+
+                        // `class A(Generic[T])`
+                        } else {
+                            let ty = class_resolver.parse_type_annotation(
+                                converted_top_level,
+                                unifier.borrow_mut(),
+                                primitives,
+                                &slice,
+                            )?;
+                            // check if it is type var
+                            let is_type_var =
+                                matches!(unifier.get_ty(ty).as_ref(), &TypeEnum::TVar { .. });
+                            if !is_type_var {
+                                return Err("expect type variable here".into());
+                            }
+
+                            // add to TopLevelDef
+                            class_def_type_vars.push(ty);
+                        }
+                    }
+
+                    // if others, do nothing in this function
+                    _ => continue,
+                }
+            }
+        }
+        Ok(())
+    }
+
+    /// step 2, base classes. Need to separate step1 and step2 for this reason:
+    /// `class B(Generic[T, V]);
+    /// class A(B[int, bool])`
+    /// if the type var associated with class `B` has not been handled properly,
+    /// the parse of type annotation of `B[int, bool]` will fail
+    fn analyze_top_level_class_bases(&mut self) -> Result<(), String> {
+        let mut def_list = self.definition_ast_list.write();
+        let converted_top_level = &self.to_top_level_context();
+        let primitives = &self.primitives;
+        let unifier = &mut self.unifier;
+
+        for (class_def, class_ast) in def_list.iter_mut() {
+            let mut class_def = class_def.write();
+            let (class_bases, class_ancestors, class_resolver) = {
+                if let TopLevelDef::Class { ancestors, resolver, .. } = class_def.deref_mut() {
+                    if let Some(ast::Located {
+                        node: ast::StmtKind::ClassDef { bases, .. }, ..
+                    }) = class_ast
+                    {
+                        (bases, ancestors, resolver)
+                    } else {
+                        unreachable!("must be both class")
+                    }
+                } else {
+                    continue;
+                }
+            };
+            let class_resolver = class_resolver.as_ref().unwrap().lock();
+            for b in class_bases {
+                // type vars have already been handled, so skip on `Generic[...]`
+                if let ast::ExprKind::Subscript { value, .. } = &b.node {
+                    if let ast::ExprKind::Name { id, .. } = &value.node {
+                        if id == "Generic" {
+                            continue;
+                        }
+                    }
+                }
+                // get the def id of the base class
+                let base_ty = class_resolver.parse_type_annotation(
+                    converted_top_level,
+                    unifier.borrow_mut(),
+                    primitives,
+                    b,
+                )?;
+                let base_id =
+                    if let TypeEnum::TObj { obj_id, .. } = unifier.get_ty(base_ty).as_ref() {
+                        *obj_id
+                    } else {
+                        return Err("expect concrete class/type to be base class".into());
+                    };
+
+                // write to the class ancestors, make sure the uniqueness
+                if !class_ancestors.contains(&base_id) {
+                    class_ancestors.push(base_id);
+                } else {
+                    return Err("cannot specify the same base class twice".into());
+                }
+            }
+        }
+        Ok(())
+    }
+
+    /// step 3, class fields and methods
+    // FIXME: analyze base classes here
+    // FIXME: deal with self type
+    // NOTE: prevent cycles only roughly done
+    fn analyze_top_level_class_fields_methods(&mut self) -> Result<(), String> {
+        let mut def_ast_list = self.definition_ast_list.write();
+        let converted_top_level = &self.to_top_level_context();
+        let primitives = &self.primitives;
+        let to_be_analyzed_class = &mut self.to_be_analyzed_class;
+        let unifier = &mut self.unifier;
+
+        // NOTE: roughly prevent infinite loop
+        let mut max_iter = to_be_analyzed_class.len() * 4;
+        'class: loop {
+            if to_be_analyzed_class.is_empty() && {
+                max_iter -= 1;
+                max_iter > 0
+            } {
+                break;
+            }
+
+            let class_ind = to_be_analyzed_class.remove(0).0;
+            let (class_name, class_body_ast, class_bases_ast, class_resolver, class_ancestors) = {
+                let (class_def, class_ast) = &mut def_ast_list[class_ind];
+                if let Some(ast::Located {
+                    node: ast::StmtKind::ClassDef { name, body, bases, .. },
+                    ..
+                }) = class_ast.as_ref()
+                {
+                    if let TopLevelDef::Class { resolver, ancestors, .. } =
+                        class_def.write().deref()
+                    {
+                        (name, body, bases, resolver.as_ref().unwrap().clone(), ancestors.clone())
+                    } else {
+                        unreachable!()
+                    }
+                } else {
+                    unreachable!("should be class def ast")
+                }
+            };
+
+            let all_base_class_analyzed = {
+                let not_yet_analyzed =
+                    to_be_analyzed_class.clone().into_iter().collect::<HashSet<_>>();
+                let base = class_ancestors.clone().into_iter().collect::<HashSet<_>>();
+                let intersection = not_yet_analyzed.intersection(&base).collect_vec();
+                intersection.is_empty()
+            };
+            if !all_base_class_analyzed {
+                to_be_analyzed_class.push(DefinitionId(class_ind));
+                continue 'class;
+            }
+
+            // get the bases type, can directly do this since it
+            // already pass the check in the previous stages
+            let class_bases_ty = class_bases_ast
+                .iter()
+                .filter_map(|x| {
+                    class_resolver
+                        .as_ref()
+                        .lock()
+                        .parse_type_annotation(
+                            converted_top_level,
+                            unifier.borrow_mut(),
+                            primitives,
+                            x,
+                        )
+                        .ok()
+                })
+                .collect_vec();
+
+            // need these vectors to check re-defining methods, class fields
+            // and store the parsed result in case some method cannot be typed for now
+            let mut class_methods_parsing_result: Vec<(String, Type, DefinitionId)> = vec![];
+            let mut class_fields_parsing_result: Vec<(String, Type)> = vec![];
+            for b in class_body_ast {
+                if let ast::StmtKind::FunctionDef {
+                    args: method_args_ast,
+                    body: method_body_ast,
+                    name: method_name,
+                    returns: method_returns_ast,
+                    ..
+                } = &b.node
+                {
+                    let arg_name_tys: Vec<(String, Type)> = {
+                        let mut result = vec![];
+                        for a in &method_args_ast.args {
+                            if a.node.arg != "self" {
+                                let annotation = a
+                                    .node
+                                    .annotation
+                                    .as_ref()
+                                    .ok_or_else(|| {
+                                        "type annotation for function parameter is needed"
+                                            .to_string()
+                                    })?
+                                    .as_ref();
+
+                                let ty = class_resolver.as_ref().lock().parse_type_annotation(
+                                    converted_top_level,
+                                    unifier.borrow_mut(),
+                                    primitives,
+                                    annotation,
+                                )?;
+                                if !Self::check_ty_analyzed(ty, unifier, to_be_analyzed_class) {
+                                    to_be_analyzed_class.push(DefinitionId(class_ind));
+                                    continue 'class;
+                                }
+                                result.push((a.node.arg.to_string(), ty));
+                            } else {
+                                // TODO: handle self, how
+                                unimplemented!()
+                            }
+                        }
+                        result
+                    };
+
+                    let method_type_var = arg_name_tys
+                        .iter()
+                        .filter_map(|(_, ty)| {
+                            let ty_enum = unifier.get_ty(*ty);
+                            if let TypeEnum::TVar { id, .. } = ty_enum.as_ref() {
+                                Some((*id, *ty))
+                            } else {
+                                None
+                            }
+                        })
+                        .collect::<Mapping<u32>>();
+
+                    let ret_ty = {
+                        if method_name != "__init__" {
+                            let ty = method_returns_ast
+                                .as_ref()
+                                .map(|x| {
+                                    class_resolver.as_ref().lock().parse_type_annotation(
+                                        converted_top_level,
+                                        unifier.borrow_mut(),
+                                        primitives,
+                                        x.as_ref(),
+                                    )
+                                })
+                                .ok_or_else(|| "return type annotation error".to_string())??;
+                            if !Self::check_ty_analyzed(ty, unifier, to_be_analyzed_class) {
+                                to_be_analyzed_class.push(DefinitionId(class_ind));
+                                continue 'class;
+                            } else {
+                                ty
+                            }
+                        } else {
+                            // TODO: __init__ function, self type, how
+                            unimplemented!()
+                        }
+                    };
+
+                    // handle fields
+                    let class_field_name_tys: Option<Vec<(String, Type)>> = if method_name
+                        == "__init__"
+                    {
+                        let mut result: Vec<(String, Type)> = vec![];
+                        for body in method_body_ast {
+                            match &body.node {
+                                ast::StmtKind::AnnAssign { target, annotation, .. }
+                                    if {
+                                        if let ast::ExprKind::Attribute { value, .. } = &target.node
+                                        {
+                                            matches!(
+                                                &value.node,
+                                                ast::ExprKind::Name { id, .. } if id == "self")
+                                        } else {
+                                            false
+                                        }
+                                    } =>
+                                {
+                                    let field_ty =
+                                        class_resolver.as_ref().lock().parse_type_annotation(
+                                            converted_top_level,
+                                            unifier.borrow_mut(),
+                                            primitives,
+                                            annotation.as_ref(),
+                                        )?;
+                                    if !Self::check_ty_analyzed(
+                                        field_ty,
+                                        unifier,
+                                        to_be_analyzed_class,
+                                    ) {
+                                        to_be_analyzed_class.push(DefinitionId(class_ind));
+                                        continue 'class;
+                                    } else {
+                                        result.push((
+                                            if let ast::ExprKind::Attribute { attr, .. } =
+                                                &target.node
+                                            {
+                                                attr.to_string()
+                                            } else {
+                                                unreachable!()
+                                            },
+                                            field_ty,
+                                        ))
+                                    }
+                                }
+
+                                // exclude those without type annotation
+                                ast::StmtKind::Assign { targets, .. }
+                                    if {
+                                        if let ast::ExprKind::Attribute { value, .. } =
+                                            &targets[0].node
+                                        {
+                                            matches!(
+                                                &value.node,
+                                                ast::ExprKind::Name {id, ..} if id == "self")
+                                        } else {
+                                            false
+                                        }
+                                    } =>
+                                {
+                                    return Err("class fields type annotation needed".into())
+                                }
+
+                                // do nothing
+                                _ => {}
+                            }
+                        }
+                        Some(result)
+                    } else {
+                        None
+                    };
+
+                    // current method all type ok, put the current method into the list
+                    if class_methods_parsing_result.iter().any(|(name, _, _)| name == method_name) {
+                        return Err("duplicate method definition".into());
+                    } else {
+                        class_methods_parsing_result.push((
+                            method_name.clone(),
+                            unifier.add_ty(TypeEnum::TFunc(
+                                FunSignature {
+                                    ret: ret_ty,
+                                    args: arg_name_tys
+                                        .into_iter()
+                                        .map(|(name, ty)| FuncArg { name, ty, default_value: None })
+                                        .collect_vec(),
+                                    vars: method_type_var,
+                                }
+                                .into(),
+                            )),
+                            *self
+                                .class_method_to_def_id
+                                .get(&Self::name_mangling(class_name.clone(), method_name))
+                                .unwrap(),
+                        ))
+                    }
+
+                    // put the fiedlds inside
+                    if let Some(class_field_name_tys) = class_field_name_tys {
+                        assert!(class_fields_parsing_result.is_empty());
+                        class_fields_parsing_result.extend(class_field_name_tys);
+                    }
+                } else {
+                    // what should we do with `class A: a = 3`?
+                    // do nothing, continue the for loop to iterate class ast
+                    continue;
+                }
+            }
+
+            // now it should be confirmed that every
+            // methods and fields of the class can be correctly typed, put the results
+            // into the actual class def method and fields field
+            let (class_def, _) = &def_ast_list[class_ind];
+            let mut class_def = class_def.write();
+            if let TopLevelDef::Class { fields, methods, .. } = class_def.deref_mut() {
+                for (ref n, ref t) in class_fields_parsing_result {
+                    fields.push((n.clone(), *t));
+                }
+                for (n, t, id) in &class_methods_parsing_result {
+                    methods.push((n.clone(), *t, *id));
+                }
+            } else {
+                unreachable!()
+            }
+
+            // change the signature field of the class methods
+            for (_, ty, id) in &class_methods_parsing_result {
+                let (method_def, _) = &def_ast_list[id.0];
+                let mut method_def = method_def.write();
+                if let TopLevelDef::Function { signature, .. } = method_def.deref_mut() {
+                    *signature = *ty;
+                }
+            }
+        }
+        Ok(())
+    }
+
+    fn analyze_top_level_function(&mut self) -> Result<(), String> {
+        unimplemented!()
+    }
+
+    fn analyze_top_level_field_instantiation(&mut self) -> Result<(), String> {
+        unimplemented!()
+    }
+
+    fn check_ty_analyzed(ty: Type, unifier: &mut Unifier, to_be_analyzed: &[DefinitionId]) -> bool {
+        let type_enum = unifier.get_ty(ty);
+        match type_enum.as_ref() {
+            TypeEnum::TObj { obj_id, .. } => !to_be_analyzed.contains(obj_id),
+            TypeEnum::TVirtual { ty } => {
+                if let TypeEnum::TObj { obj_id, .. } = unifier.get_ty(*ty).as_ref() {
+                    !to_be_analyzed.contains(obj_id)
+                } else {
+                    unreachable!()
+                }
+            }
+            TypeEnum::TVar { .. } => true,
+            _ => unreachable!(),
+        }
+    }
+}

nac3core/src/typecheck/function_check.rs

@@ -0,0 +1,216 @@
+use super::type_inferencer::Inferencer;
+use super::typedef::Type;
+use rustpython_parser::ast::{self, Expr, ExprKind, Stmt, StmtKind};
+use std::iter::once;
+
+impl<'a> Inferencer<'a> {
+    fn check_pattern(
+        &mut self,
+        pattern: &Expr<Option<Type>>,
+        defined_identifiers: &mut Vec<String>,
+    ) -> Result<(), String> {
+        match &pattern.node {
+            ExprKind::Name { id, .. } => {
+                if !defined_identifiers.contains(id) {
+                    defined_identifiers.push(id.clone());
+                }
+                Ok(())
+            }
+            ExprKind::Tuple { elts, .. } => {
+                for elt in elts.iter() {
+                    self.check_pattern(elt, defined_identifiers)?;
+                }
+                Ok(())
+            }
+            _ => self.check_expr(pattern, defined_identifiers),
+        }
+    }
+
+    fn check_expr(
+        &mut self,
+        expr: &Expr<Option<Type>>,
+        defined_identifiers: &[String],
+    ) -> Result<(), String> {
+        // there are some cases where the custom field is None
+        if let Some(ty) = &expr.custom {
+            if !self.unifier.is_concrete(*ty, &self.function_data.bound_variables) {
+                return Err(format!(
+                    "expected concrete type at {} but got {}",
+                    expr.location,
+                    self.unifier.get_ty(*ty).get_type_name()
+                ));
+            }
+        }
+        match &expr.node {
+            ExprKind::Name { id, .. } => {
+                if !defined_identifiers.contains(id) {
+                    return Err(format!(
+                        "unknown identifier {} (use before def?) at {}",
+                        id, expr.location
+                    ));
+                }
+            }
+            ExprKind::List { elts, .. }
+            | ExprKind::Tuple { elts, .. }
+            | ExprKind::BoolOp { values: elts, .. } => {
+                for elt in elts.iter() {
+                    self.check_expr(elt, defined_identifiers)?;
+                }
+            }
+            ExprKind::Attribute { value, .. } => {
+                self.check_expr(value, defined_identifiers)?;
+            }
+            ExprKind::BinOp { left, right, .. } => {
+                self.check_expr(left, defined_identifiers)?;
+                self.check_expr(right, defined_identifiers)?;
+            }
+            ExprKind::UnaryOp { operand, .. } => {
+                self.check_expr(operand, defined_identifiers)?;
+            }
+            ExprKind::Compare { left, comparators, .. } => {
+                for elt in once(left.as_ref()).chain(comparators.iter()) {
+                    self.check_expr(elt, defined_identifiers)?;
+                }
+            }
+            ExprKind::Subscript { value, slice, .. } => {
+                self.check_expr(value, defined_identifiers)?;
+                self.check_expr(slice, defined_identifiers)?;
+            }
+            ExprKind::IfExp { test, body, orelse } => {
+                self.check_expr(test, defined_identifiers)?;
+                self.check_expr(body, defined_identifiers)?;
+                self.check_expr(orelse, defined_identifiers)?;
+            }
+            ExprKind::Slice { lower, upper, step } => {
+                for elt in [lower.as_ref(), upper.as_ref(), step.as_ref()].iter().flatten() {
+                    self.check_expr(elt, defined_identifiers)?;
+                }
+            }
+            ExprKind::Lambda { args, body } => {
+                let mut defined_identifiers = defined_identifiers.to_vec();
+                for arg in args.args.iter() {
+                    if !defined_identifiers.contains(&arg.node.arg) {
+                        defined_identifiers.push(arg.node.arg.clone());
+                    }
+                }
+                self.check_expr(body, &defined_identifiers)?;
+            }
+            ExprKind::ListComp { elt, generators, .. } => {
+                // in our type inference stage, we already make sure that there is only 1 generator
+                let ast::Comprehension { target, iter, ifs, .. } = &generators[0];
+                self.check_expr(iter, defined_identifiers)?;
+                let mut defined_identifiers = defined_identifiers.to_vec();
+                self.check_pattern(target, &mut defined_identifiers)?;
+                for term in once(elt.as_ref()).chain(ifs.iter()) {
+                    self.check_expr(term, &defined_identifiers)?;
+                }
+            }
+            ExprKind::Call { func, args, keywords } => {
+                for expr in once(func.as_ref())
+                    .chain(args.iter())
+                    .chain(keywords.iter().map(|v| v.node.value.as_ref()))
+                {
+                    self.check_expr(expr, defined_identifiers)?;
+                }
+            }
+            ExprKind::Constant { .. } => {}
+            _ => {
+                println!("{:?}", expr.node);
+                unimplemented!()
+            }
+        }
+        Ok(())
+    }
+
+    // check statements for proper identifier def-use and return on all paths
+    fn check_stmt(
+        &mut self,
+        stmt: &Stmt<Option<Type>>,
+        defined_identifiers: &mut Vec<String>,
+    ) -> Result<bool, String> {
+        match &stmt.node {
+            StmtKind::For { target, iter, body, orelse, .. } => {
+                self.check_expr(iter, defined_identifiers)?;
+                for stmt in orelse.iter() {
+                    self.check_stmt(stmt, defined_identifiers)?;
+                }
+                let mut defined_identifiers = defined_identifiers.clone();
+                self.check_pattern(target, &mut defined_identifiers)?;
+                for stmt in body.iter() {
+                    self.check_stmt(stmt, &mut defined_identifiers)?;
+                }
+                Ok(false)
+            }
+            StmtKind::If { test, body, orelse } => {
+                self.check_expr(test, defined_identifiers)?;
+                let mut body_identifiers = defined_identifiers.clone();
+                let mut orelse_identifiers = defined_identifiers.clone();
+                let body_returned = self.check_block(body, &mut body_identifiers)?;
+                let orelse_returned = self.check_block(orelse, &mut orelse_identifiers)?;
+
+                for ident in body_identifiers.iter() {
+                    if !defined_identifiers.contains(ident) && orelse_identifiers.contains(ident) {
+                        defined_identifiers.push(ident.clone())
+                    }
+                }
+                Ok(body_returned && orelse_returned)
+            }
+            StmtKind::While { test, body, orelse } => {
+                self.check_expr(test, defined_identifiers)?;
+                let mut defined_identifiers = defined_identifiers.clone();
+                self.check_block(body, &mut defined_identifiers)?;
+                self.check_block(orelse, &mut defined_identifiers)?;
+                Ok(false)
+            }
+            StmtKind::Expr { value } => {
+                self.check_expr(value, defined_identifiers)?;
+                Ok(false)
+            }
+            StmtKind::Assign { targets, value, .. } => {
+                self.check_expr(value, defined_identifiers)?;
+                for target in targets {
+                    self.check_pattern(target, defined_identifiers)?;
+                }
+                Ok(false)
+            }
+            StmtKind::AnnAssign { target, value, .. } => {
+                if let Some(value) = value {
+                    self.check_expr(value, defined_identifiers)?;
+                    self.check_pattern(target, defined_identifiers)?;
+                }
+                Ok(false)
+            }
+            StmtKind::Return { value } => {
+                if let Some(value) = value {
+                    self.check_expr(value, defined_identifiers)?;
+                }
+                Ok(true)
+            }
+            StmtKind::Raise { exc, .. } => {
+                if let Some(value) = exc {
+                    self.check_expr(value, defined_identifiers)?;
+                }
+                Ok(true)
+            }
+            // break, raise, etc.
+            _ => Ok(false),
+        }
+    }
+
+    pub fn check_block(
+        &mut self,
+        block: &[Stmt<Option<Type>>],
+        defined_identifiers: &mut Vec<String>,
+    ) -> Result<bool, String> {
+        let mut ret = false;
+        for stmt in block {
+            if ret {
+                return Err(format!("dead code at {:?}", stmt.location));
+            }
+            if self.check_stmt(stmt, defined_identifiers)? {
+                ret = true;
+            }
+        }
+        Ok(ret)
+    }
+}

nac3core/src/typecheck/magic_methods.rs

@@ -0,0 +1,322 @@
+use crate::typecheck::{
+    type_inferencer::*,
+    typedef::{FunSignature, FuncArg, Type, TypeEnum, Unifier},
+};
+use rustpython_parser::ast;
+use rustpython_parser::ast::{Cmpop, Operator, Unaryop};
+use std::borrow::Borrow;
+use std::collections::HashMap;
+
+pub fn binop_name(op: &Operator) -> &'static str {
+    match op {
+        Operator::Add => "__add__",
+        Operator::Sub => "__sub__",
+        Operator::Div => "__truediv__",
+        Operator::Mod => "__mod__",
+        Operator::Mult => "__mul__",
+        Operator::Pow => "__pow__",
+        Operator::BitOr => "__or__",
+        Operator::BitXor => "__xor__",
+        Operator::BitAnd => "__and__",
+        Operator::LShift => "__lshift__",
+        Operator::RShift => "__rshift__",
+        Operator::FloorDiv => "__floordiv__",
+        Operator::MatMult => "__matmul__",
+    }
+}
+
+pub fn binop_assign_name(op: &Operator) -> &'static str {
+    match op {
+        Operator::Add => "__iadd__",
+        Operator::Sub => "__isub__",
+        Operator::Div => "__itruediv__",
+        Operator::Mod => "__imod__",
+        Operator::Mult => "__imul__",
+        Operator::Pow => "__ipow__",
+        Operator::BitOr => "__ior__",
+        Operator::BitXor => "__ixor__",
+        Operator::BitAnd => "__iand__",
+        Operator::LShift => "__ilshift__",
+        Operator::RShift => "__irshift__",
+        Operator::FloorDiv => "__ifloordiv__",
+        Operator::MatMult => "__imatmul__",
+    }
+}
+
+pub fn unaryop_name(op: &Unaryop) -> &'static str {
+    match op {
+        Unaryop::UAdd => "__pos__",
+        Unaryop::USub => "__neg__",
+        Unaryop::Not => "__not__",
+        Unaryop::Invert => "__inv__",
+    }
+}
+
+pub fn comparison_name(op: &Cmpop) -> Option<&'static str> {
+    match op {
+        Cmpop::Lt => Some("__lt__"),
+        Cmpop::LtE => Some("__le__"),
+        Cmpop::Gt => Some("__gt__"),
+        Cmpop::GtE => Some("__ge__"),
+        Cmpop::Eq => Some("__eq__"),
+        Cmpop::NotEq => Some("__ne__"),
+        _ => None,
+    }
+}
+
+pub fn impl_binop(
+    unifier: &mut Unifier,
+    store: &PrimitiveStore,
+    ty: Type,
+    other_ty: &[Type],
+    ret_ty: Type,
+    ops: &[ast::Operator],
+) {
+    if let TypeEnum::TObj { fields, .. } = unifier.get_ty(ty).borrow() {
+        let (other_ty, other_var_id) = if other_ty.len() == 1 {
+            (other_ty[0], None)
+        } else {
+            let (ty, var_id) = unifier.get_fresh_var_with_range(other_ty);
+            (ty, Some(var_id))
+        };
+        let function_vars = if let Some(var_id) = other_var_id {
+            vec![(var_id, other_ty)].into_iter().collect::<HashMap<_, _>>()
+        } else {
+            HashMap::new()
+        };
+        for op in ops {
+            fields.borrow_mut().insert(binop_name(op).into(), {
+                unifier.add_ty(TypeEnum::TFunc(
+                    FunSignature {
+                        ret: ret_ty,
+                        vars: function_vars.clone(),
+                        args: vec![FuncArg {
+                            ty: other_ty,
+                            default_value: None,
+                            name: "other".into(),
+                        }],
+                    }
+                    .into(),
+                ))
+            });
+
+            fields.borrow_mut().insert(binop_assign_name(op).into(), {
+                unifier.add_ty(TypeEnum::TFunc(
+                    FunSignature {
+                        ret: store.none,
+                        vars: function_vars.clone(),
+                        args: vec![FuncArg {
+                            ty: other_ty,
+                            default_value: None,
+                            name: "other".into(),
+                        }],
+                    }
+                    .into(),
+                ))
+            });
+        }
+    } else {
+        unreachable!("")
+    }
+}
+
+pub fn impl_unaryop(
+    unifier: &mut Unifier,
+    _store: &PrimitiveStore,
+    ty: Type,
+    ret_ty: Type,
+    ops: &[ast::Unaryop],
+) {
+    if let TypeEnum::TObj { fields, .. } = unifier.get_ty(ty).borrow() {
+        for op in ops {
+            fields.borrow_mut().insert(
+                unaryop_name(op).into(),
+                unifier.add_ty(TypeEnum::TFunc(
+                    FunSignature { ret: ret_ty, vars: HashMap::new(), args: vec![] }.into(),
+                )),
+            );
+        }
+    } else {
+        unreachable!()
+    }
+}
+
+pub fn impl_cmpop(
+    unifier: &mut Unifier,
+    store: &PrimitiveStore,
+    ty: Type,
+    other_ty: Type,
+    ops: &[ast::Cmpop],
+) {
+    if let TypeEnum::TObj { fields, .. } = unifier.get_ty(ty).borrow() {
+        for op in ops {
+            fields.borrow_mut().insert(
+                comparison_name(op).unwrap().into(),
+                unifier.add_ty(TypeEnum::TFunc(
+                    FunSignature {
+                        ret: store.bool,
+                        vars: HashMap::new(),
+                        args: vec![FuncArg {
+                            ty: other_ty,
+                            default_value: None,
+                            name: "other".into(),
+                        }],
+                    }
+                    .into(),
+                )),
+            );
+        }
+    } else {
+        unreachable!()
+    }
+}
+
+/// Add, Sub, Mult, Pow
+pub fn impl_basic_arithmetic(
+    unifier: &mut Unifier,
+    store: &PrimitiveStore,
+    ty: Type,
+    other_ty: &[Type],
+    ret_ty: Type,
+) {
+    impl_binop(
+        unifier,
+        store,
+        ty,
+        other_ty,
+        ret_ty,
+        &[ast::Operator::Add, ast::Operator::Sub, ast::Operator::Mult],
+    )
+}
+
+pub fn impl_pow(
+    unifier: &mut Unifier,
+    store: &PrimitiveStore,
+    ty: Type,
+    other_ty: &[Type],
+    ret_ty: Type,
+) {
+    impl_binop(unifier, store, ty, other_ty, ret_ty, &[ast::Operator::Pow])
+}
+
+/// BitOr, BitXor, BitAnd
+pub fn impl_bitwise_arithmetic(unifier: &mut Unifier, store: &PrimitiveStore, ty: Type) {
+    impl_binop(
+        unifier,
+        store,
+        ty,
+        &[ty],
+        ty,
+        &[ast::Operator::BitAnd, ast::Operator::BitOr, ast::Operator::BitXor],
+    )
+}
+
+/// LShift, RShift
+pub fn impl_bitwise_shift(unifier: &mut Unifier, store: &PrimitiveStore, ty: Type) {
+    impl_binop(unifier, store, ty, &[ty], ty, &[ast::Operator::LShift, ast::Operator::RShift])
+}
+
+/// Div
+pub fn impl_div(unifier: &mut Unifier, store: &PrimitiveStore, ty: Type, other_ty: &[Type]) {
+    impl_binop(unifier, store, ty, other_ty, store.float, &[ast::Operator::Div])
+}
+
+/// FloorDiv
+pub fn impl_floordiv(
+    unifier: &mut Unifier,
+    store: &PrimitiveStore,
+    ty: Type,
+    other_ty: &[Type],
+    ret_ty: Type,
+) {
+    impl_binop(unifier, store, ty, other_ty, ret_ty, &[ast::Operator::FloorDiv])
+}
+
+/// Mod
+pub fn impl_mod(
+    unifier: &mut Unifier,
+    store: &PrimitiveStore,
+    ty: Type,
+    other_ty: &[Type],
+    ret_ty: Type,
+) {
+    impl_binop(unifier, store, ty, other_ty, ret_ty, &[ast::Operator::Mod])
+}
+
+/// UAdd, USub
+pub fn impl_sign(unifier: &mut Unifier, store: &PrimitiveStore, ty: Type) {
+    impl_unaryop(unifier, store, ty, ty, &[ast::Unaryop::UAdd, ast::Unaryop::USub])
+}
+
+/// Invert
+pub fn impl_invert(unifier: &mut Unifier, store: &PrimitiveStore, ty: Type) {
+    impl_unaryop(unifier, store, ty, ty, &[ast::Unaryop::Invert])
+}
+
+/// Not
+pub fn impl_not(unifier: &mut Unifier, store: &PrimitiveStore, ty: Type) {
+    impl_unaryop(unifier, store, ty, store.bool, &[ast::Unaryop::Not])
+}
+
+/// Lt, LtE, Gt, GtE
+pub fn impl_comparison(unifier: &mut Unifier, store: &PrimitiveStore, ty: Type, other_ty: Type) {
+    impl_cmpop(
+        unifier,
+        store,
+        ty,
+        other_ty,
+        &[ast::Cmpop::Lt, ast::Cmpop::Gt, ast::Cmpop::LtE, ast::Cmpop::GtE],
+    )
+}
+
+/// Eq, NotEq
+pub fn impl_eq(unifier: &mut Unifier, store: &PrimitiveStore, ty: Type) {
+    impl_cmpop(unifier, store, ty, ty, &[ast::Cmpop::Eq, ast::Cmpop::NotEq])
+}
+
+pub fn set_primitives_magic_methods(store: &PrimitiveStore, unifier: &mut Unifier) {
+    let PrimitiveStore { int32: int32_t, int64: int64_t, float: float_t, bool: bool_t, .. } =
+        *store;
+    /* int32 ======== */
+    impl_basic_arithmetic(unifier, store, int32_t, &[int32_t], int32_t);
+    impl_pow(unifier, store, int32_t, &[int32_t], int32_t);
+    impl_bitwise_arithmetic(unifier, store, int32_t);
+    impl_bitwise_shift(unifier, store, int32_t);
+    impl_div(unifier, store, int32_t, &[int32_t]);
+    impl_floordiv(unifier, store, int32_t, &[int32_t], int32_t);
+    impl_mod(unifier, store, int32_t, &[int32_t], int32_t);
+    impl_sign(unifier, store, int32_t);
+    impl_invert(unifier, store, int32_t);
+    impl_not(unifier, store, int32_t);
+    impl_comparison(unifier, store, int32_t, int32_t);
+    impl_eq(unifier, store, int32_t);
+
+    /* int64 ======== */
+    impl_basic_arithmetic(unifier, store, int64_t, &[int64_t], int64_t);
+    impl_pow(unifier, store, int64_t, &[int64_t], int64_t);
+    impl_bitwise_arithmetic(unifier, store, int64_t);
+    impl_bitwise_shift(unifier, store, int64_t);
+    impl_div(unifier, store, int64_t, &[int64_t]);
+    impl_floordiv(unifier, store, int64_t, &[int64_t], int64_t);
+    impl_mod(unifier, store, int64_t, &[int64_t], int64_t);
+    impl_sign(unifier, store, int64_t);
+    impl_invert(unifier, store, int64_t);
+    impl_not(unifier, store, int64_t);
+    impl_comparison(unifier, store, int64_t, int64_t);
+    impl_eq(unifier, store, int64_t);
+
+    /* float ======== */
+    impl_basic_arithmetic(unifier, store, float_t, &[float_t], float_t);
+    impl_pow(unifier, store, float_t, &[int32_t, float_t], float_t);
+    impl_div(unifier, store, float_t, &[float_t]);
+    impl_floordiv(unifier, store, float_t, &[float_t], float_t);
+    impl_mod(unifier, store, float_t, &[float_t], float_t);
+    impl_sign(unifier, store, float_t);
+    impl_not(unifier, store, float_t);
+    impl_comparison(unifier, store, float_t, float_t);
+    impl_eq(unifier, store, float_t);
+
+    /* bool ======== */
+    impl_not(unifier, store, bool_t);
+    impl_eq(unifier, store, bool_t);
+}

nac3core/src/typecheck/mod.rs

@@ -0,0 +1,5 @@
+mod function_check;
+pub mod magic_methods;
+pub mod type_inferencer;
+pub mod typedef;
+mod unification_table;

nac3core/src/typecheck/type_inferencer/mod.rs

@@ -0,0 +1,582 @@
+use std::collections::HashMap;
+use std::convert::{From, TryInto};
+use std::iter::once;
+use std::{cell::RefCell, sync::Arc};
+
+use super::typedef::{Call, FunSignature, FuncArg, Type, TypeEnum, Unifier};
+use super::{magic_methods::*, typedef::CallId};
+use crate::{symbol_resolver::SymbolResolver, top_level::TopLevelContext};
+use itertools::izip;
+use rustpython_parser::ast::{
+    self,
+    fold::{self, Fold},
+    Arguments, Comprehension, ExprKind, Located, Location,
+};
+
+#[cfg(test)]
+mod test;
+
+#[derive(PartialEq, Eq, Hash, Copy, Clone, Debug)]
+pub struct CodeLocation {
+    row: usize,
+    col: usize,
+}
+
+impl From<Location> for CodeLocation {
+    fn from(loc: Location) -> CodeLocation {
+        CodeLocation { row: loc.row(), col: loc.column() }
+    }
+}
+
+#[derive(Clone, Copy)]
+pub struct PrimitiveStore {
+    pub int32: Type,
+    pub int64: Type,
+    pub float: Type,
+    pub bool: Type,
+    pub none: Type,
+}
+
+pub struct FunctionData {
+    pub resolver: Arc<dyn SymbolResolver + Send + Sync>,
+    pub return_type: Option<Type>,
+    pub bound_variables: Vec<Type>,
+}
+
+pub struct Inferencer<'a> {
+    pub top_level: &'a TopLevelContext,
+    pub function_data: &'a mut FunctionData,
+    pub unifier: &'a mut Unifier,
+    pub primitives: &'a PrimitiveStore,
+    pub virtual_checks: &'a mut Vec<(Type, Type)>,
+    pub variable_mapping: HashMap<String, Type>,
+    pub calls: &'a mut HashMap<CodeLocation, CallId>,
+}
+
+struct NaiveFolder();
+impl fold::Fold<()> for NaiveFolder {
+    type TargetU = Option<Type>;
+    type Error = String;
+    fn map_user(&mut self, _: ()) -> Result<Self::TargetU, Self::Error> {
+        Ok(None)
+    }
+}
+
+impl<'a> fold::Fold<()> for Inferencer<'a> {
+    type TargetU = Option<Type>;
+    type Error = String;
+
+    fn map_user(&mut self, _: ()) -> Result<Self::TargetU, Self::Error> {
+        Ok(None)
+    }
+
+    fn fold_stmt(&mut self, node: ast::Stmt<()>) -> Result<ast::Stmt<Self::TargetU>, Self::Error> {
+        let stmt = match node.node {
+            // we don't want fold over type annotation
+            ast::StmtKind::AnnAssign { target, annotation, value, simple } => {
+                let target = Box::new(self.fold_expr(*target)?);
+                let value = if let Some(v) = value {
+                    let ty = Box::new(self.fold_expr(*v)?);
+                    self.unifier.unify(target.custom.unwrap(), ty.custom.unwrap())?;
+                    Some(ty)
+                } else {
+                    None
+                };
+                let annotation_type = self.function_data.resolver.parse_type_annotation(
+                    self.top_level,
+                    self.unifier,
+                    &self.primitives,
+                    annotation.as_ref(),
+                )?;
+                self.unifier.unify(annotation_type, target.custom.unwrap())?;
+                let annotation = Box::new(NaiveFolder().fold_expr(*annotation)?);
+                Located {
+                    location: node.location,
+                    custom: None,
+                    node: ast::StmtKind::AnnAssign { target, annotation, value, simple },
+                }
+            }
+            _ => fold::fold_stmt(self, node)?,
+        };
+        match &stmt.node {
+            ast::StmtKind::For { target, iter, .. } => {
+                let list = self.unifier.add_ty(TypeEnum::TList { ty: target.custom.unwrap() });
+                self.unifier.unify(list, iter.custom.unwrap())?;
+            }
+            ast::StmtKind::If { test, .. } | ast::StmtKind::While { test, .. } => {
+                self.unifier.unify(test.custom.unwrap(), self.primitives.bool)?;
+            }
+            ast::StmtKind::Assign { targets, value, .. } => {
+                for target in targets.iter() {
+                    self.unifier.unify(target.custom.unwrap(), value.custom.unwrap())?;
+                }
+            }
+            ast::StmtKind::AnnAssign { .. } | ast::StmtKind::Expr { .. } => {}
+            ast::StmtKind::Break | ast::StmtKind::Continue => {}
+            ast::StmtKind::Return { value } => match (value, self.function_data.return_type) {
+                (Some(v), Some(v1)) => {
+                    self.unifier.unify(v.custom.unwrap(), v1)?;
+                }
+                (Some(_), None) => {
+                    return Err("Unexpected return value".to_string());
+                }
+                (None, Some(_)) => {
+                    return Err("Expected return value".to_string());
+                }
+                (None, None) => {}
+            },
+            _ => return Err("Unsupported statement type".to_string()),
+        };
+        Ok(stmt)
+    }
+
+    fn fold_expr(&mut self, node: ast::Expr<()>) -> Result<ast::Expr<Self::TargetU>, Self::Error> {
+        let expr = match node.node {
+            ast::ExprKind::Call { func, args, keywords } => {
+                return self.fold_call(node.location, *func, args, keywords);
+            }
+            ast::ExprKind::Lambda { args, body } => {
+                return self.fold_lambda(node.location, *args, *body);
+            }
+            ast::ExprKind::ListComp { elt, generators } => {
+                return self.fold_listcomp(node.location, *elt, generators);
+            }
+            _ => fold::fold_expr(self, node)?,
+        };
+        let custom = match &expr.node {
+            ast::ExprKind::Constant { value, .. } => Some(self.infer_constant(value)?),
+            ast::ExprKind::Name { id, .. } => Some(self.infer_identifier(id)?),
+            ast::ExprKind::List { elts, .. } => Some(self.infer_list(elts)?),
+            ast::ExprKind::Tuple { elts, .. } => Some(self.infer_tuple(elts)?),
+            ast::ExprKind::Attribute { value, attr, ctx: _ } => {
+                Some(self.infer_attribute(value, attr)?)
+            }
+            ast::ExprKind::BoolOp { values, .. } => Some(self.infer_bool_ops(values)?),
+            ast::ExprKind::BinOp { left, op, right } => Some(self.infer_bin_ops(left, op, right)?),
+            ast::ExprKind::UnaryOp { op, operand } => Some(self.infer_unary_ops(op, operand)?),
+            ast::ExprKind::Compare { left, ops, comparators } => {
+                Some(self.infer_compare(left, ops, comparators)?)
+            }
+            ast::ExprKind::Subscript { value, slice, .. } => {
+                Some(self.infer_subscript(value.as_ref(), slice.as_ref())?)
+            }
+            ast::ExprKind::IfExp { test, body, orelse } => {
+                Some(self.infer_if_expr(test, body.as_ref(), orelse.as_ref())?)
+            }
+            ast::ExprKind::ListComp { .. }
+            | ast::ExprKind::Lambda { .. }
+            | ast::ExprKind::Call { .. } => expr.custom, // already computed
+            ast::ExprKind::Slice { .. } => None, // we don't need it for slice
+            _ => return Err("not supported yet".into()),
+        };
+        Ok(ast::Expr { custom, location: expr.location, node: expr.node })
+    }
+}
+
+type InferenceResult = Result<Type, String>;
+
+impl<'a> Inferencer<'a> {
+    /// Constrain a <: b
+    /// Currently implemented as unification
+    fn constrain(&mut self, a: Type, b: Type) -> Result<(), String> {
+        self.unifier.unify(a, b)
+    }
+
+    fn build_method_call(
+        &mut self,
+        location: Location,
+        method: String,
+        obj: Type,
+        params: Vec<Type>,
+        ret: Type,
+    ) -> InferenceResult {
+        let call = self.unifier.add_call(Call {
+            posargs: params,
+            kwargs: HashMap::new(),
+            ret,
+            fun: RefCell::new(None),
+        });
+        self.calls.insert(location.into(), call);
+        let call = self.unifier.add_ty(TypeEnum::TCall(vec![call].into()));
+        let fields = once((method, call)).collect();
+        let record = self.unifier.add_record(fields);
+        self.constrain(obj, record)?;
+        Ok(ret)
+    }
+
+    fn fold_lambda(
+        &mut self,
+        location: Location,
+        args: Arguments,
+        body: ast::Expr<()>,
+    ) -> Result<ast::Expr<Option<Type>>, String> {
+        if !args.posonlyargs.is_empty()
+            || args.vararg.is_some()
+            || !args.kwonlyargs.is_empty()
+            || args.kwarg.is_some()
+            || !args.defaults.is_empty()
+        {
+            // actually I'm not sure whether programs violating this is a valid python program.
+            return Err(
+                "We only support positional or keyword arguments without defaults for lambdas."
+                    .to_string(),
+            );
+        }
+
+        let fn_args: Vec<_> = args
+            .args
+            .iter()
+            .map(|v| (v.node.arg.clone(), self.unifier.get_fresh_var().0))
+            .collect();
+        let mut variable_mapping = self.variable_mapping.clone();
+        variable_mapping.extend(fn_args.iter().cloned());
+        let ret = self.unifier.get_fresh_var().0;
+        let mut new_context = Inferencer {
+            function_data: self.function_data,
+            unifier: self.unifier,
+            primitives: self.primitives,
+            virtual_checks: self.virtual_checks,
+            calls: self.calls,
+            top_level: self.top_level,
+            variable_mapping,
+        };
+        let fun = FunSignature {
+            args: fn_args
+                .iter()
+                .map(|(k, ty)| FuncArg { name: k.clone(), ty: *ty, default_value: None })
+                .collect(),
+            ret,
+            vars: Default::default(),
+        };
+        let body = new_context.fold_expr(body)?;
+        new_context.unifier.unify(fun.ret, body.custom.unwrap())?;
+        let mut args = new_context.fold_arguments(args)?;
+        for (arg, (name, ty)) in args.args.iter_mut().zip(fn_args.iter()) {
+            assert_eq!(&arg.node.arg, name);
+            arg.custom = Some(*ty);
+        }
+        Ok(Located {
+            location,
+            node: ExprKind::Lambda { args: args.into(), body: body.into() },
+            custom: Some(self.unifier.add_ty(TypeEnum::TFunc(fun.into()))),
+        })
+    }
+
+    fn fold_listcomp(
+        &mut self,
+        location: Location,
+        elt: ast::Expr<()>,
+        mut generators: Vec<Comprehension>,
+    ) -> Result<ast::Expr<Option<Type>>, String> {
+        if generators.len() != 1 {
+            return Err(
+                "Only 1 generator statement for list comprehension is supported.".to_string()
+            );
+        }
+        let variable_mapping = self.variable_mapping.clone();
+        let mut new_context = Inferencer {
+            function_data: self.function_data,
+            unifier: self.unifier,
+            virtual_checks: self.virtual_checks,
+            top_level: self.top_level,
+            variable_mapping,
+            primitives: self.primitives,
+            calls: self.calls,
+        };
+        let elt = new_context.fold_expr(elt)?;
+        let generator = generators.pop().unwrap();
+        if generator.is_async {
+            return Err("Async iterator not supported.".to_string());
+        }
+        let target = new_context.fold_expr(*generator.target)?;
+        let iter = new_context.fold_expr(*generator.iter)?;
+        let ifs: Vec<_> = generator
+            .ifs
+            .into_iter()
+            .map(|v| new_context.fold_expr(v))
+            .collect::<Result<_, _>>()?;
+
+        // iter should be a list of targets...
+        // actually it should be an iterator of targets, but we don't have iter type for now
+        let list = new_context.unifier.add_ty(TypeEnum::TList { ty: target.custom.unwrap() });
+        new_context.unifier.unify(iter.custom.unwrap(), list)?;
+        // if conditions should be bool
+        for v in ifs.iter() {
+            new_context.unifier.unify(v.custom.unwrap(), new_context.primitives.bool)?;
+        }
+
+        Ok(Located {
+            location,
+            custom: Some(new_context.unifier.add_ty(TypeEnum::TList { ty: elt.custom.unwrap() })),
+            node: ExprKind::ListComp {
+                elt: Box::new(elt),
+                generators: vec![ast::Comprehension {
+                    target: Box::new(target),
+                    iter: Box::new(iter),
+                    ifs,
+                    is_async: false,
+                }],
+            },
+        })
+    }
+
+    fn fold_call(
+        &mut self,
+        location: Location,
+        func: ast::Expr<()>,
+        mut args: Vec<ast::Expr<()>>,
+        keywords: Vec<Located<ast::KeywordData>>,
+    ) -> Result<ast::Expr<Option<Type>>, String> {
+        let func =
+            if let Located { location: func_location, custom, node: ExprKind::Name { id, ctx } } =
+                func
+            {
+                // handle special functions that cannot be typed in the usual way...
+                if id == "virtual" {
+                    if args.is_empty() || args.len() > 2 || !keywords.is_empty() {
+                        return Err(
+                            "`virtual` can only accept 1/2 positional arguments.".to_string()
+                        );
+                    }
+                    let arg0 = self.fold_expr(args.remove(0))?;
+                    let ty = if let Some(arg) = args.pop() {
+                        self.function_data.resolver.parse_type_annotation(
+                            self.top_level,
+                            self.unifier,
+                            self.primitives,
+                            &arg,
+                        )?
+                    } else {
+                        self.unifier.get_fresh_var().0
+                    };
+                    self.virtual_checks.push((arg0.custom.unwrap(), ty));
+                    let custom = Some(self.unifier.add_ty(TypeEnum::TVirtual { ty }));
+                    return Ok(Located {
+                        location,
+                        custom,
+                        node: ExprKind::Call {
+                            func: Box::new(Located {
+                                custom: None,
+                                location: func.location,
+                                node: ExprKind::Name { id, ctx },
+                            }),
+                            args: vec![arg0],
+                            keywords: vec![],
+                        },
+                    });
+                }
+                // int64 is special because its argument can be a constant larger than int32
+                if id == "int64" && args.len() == 1 {
+                    if let ExprKind::Constant { value: ast::Constant::Int(val), kind } =
+                        &args[0].node
+                    {
+                        let int64: Result<i64, _> = val.try_into();
+                        let custom;
+                        if int64.is_ok() {
+                            custom = Some(self.primitives.int64);
+                        } else {
+                            return Err("Integer out of bound".into());
+                        }
+                        return Ok(Located {
+                            location: args[0].location,
+                            custom,
+                            node: ExprKind::Constant {
+                                value: ast::Constant::Int(val.clone()),
+                                kind: kind.clone(),
+                            },
+                        });
+                    }
+                }
+                Located { location: func_location, custom, node: ExprKind::Name { id, ctx } }
+            } else {
+                func
+            };
+        let func = Box::new(self.fold_expr(func)?);
+        let args = args.into_iter().map(|v| self.fold_expr(v)).collect::<Result<Vec<_>, _>>()?;
+        let keywords = keywords
+            .into_iter()
+            .map(|v| fold::fold_keyword(self, v))
+            .collect::<Result<Vec<_>, _>>()?;
+        let ret = self.unifier.get_fresh_var().0;
+        let call = self.unifier.add_call(Call {
+            posargs: args.iter().map(|v| v.custom.unwrap()).collect(),
+            kwargs: keywords
+                .iter()
+                .map(|v| (v.node.arg.as_ref().unwrap().clone(), v.custom.unwrap()))
+                .collect(),
+            fun: RefCell::new(None),
+            ret,
+        });
+        self.calls.insert(location.into(), call);
+        let call = self.unifier.add_ty(TypeEnum::TCall(vec![call].into()));
+        self.unifier.unify(func.custom.unwrap(), call)?;
+
+        Ok(Located { location, custom: Some(ret), node: ExprKind::Call { func, args, keywords } })
+    }
+
+    fn infer_identifier(&mut self, id: &str) -> InferenceResult {
+        if let Some(ty) = self.variable_mapping.get(id) {
+            Ok(*ty)
+        } else {
+            Ok(self
+                .function_data
+                .resolver
+                .get_symbol_type(self.unifier, self.primitives, id)
+                .unwrap_or_else(|| {
+                    let ty = self.unifier.get_fresh_var().0;
+                    self.variable_mapping.insert(id.to_string(), ty);
+                    ty
+                }))
+        }
+    }
+
+    fn infer_constant(&mut self, constant: &ast::Constant) -> InferenceResult {
+        match constant {
+            ast::Constant::Bool(_) => Ok(self.primitives.bool),
+            ast::Constant::Int(val) => {
+                let int32: Result<i32, _> = val.try_into();
+                // int64 would be handled separately in functions
+                if int32.is_ok() {
+                    Ok(self.primitives.int32)
+                } else {
+                    Err("Integer out of bound".into())
+                }
+            }
+            ast::Constant::Float(_) => Ok(self.primitives.float),
+            ast::Constant::Tuple(vals) => {
+                let ty: Result<Vec<_>, _> = vals.iter().map(|x| self.infer_constant(x)).collect();
+                Ok(self.unifier.add_ty(TypeEnum::TTuple { ty: ty? }))
+            }
+            _ => Err("not supported".into()),
+        }
+    }
+
+    fn infer_list(&mut self, elts: &[ast::Expr<Option<Type>>]) -> InferenceResult {
+        let (ty, _) = self.unifier.get_fresh_var();
+        for t in elts.iter() {
+            self.unifier.unify(ty, t.custom.unwrap())?;
+        }
+        Ok(self.unifier.add_ty(TypeEnum::TList { ty }))
+    }
+
+    fn infer_tuple(&mut self, elts: &[ast::Expr<Option<Type>>]) -> InferenceResult {
+        let ty = elts.iter().map(|x| x.custom.unwrap()).collect();
+        Ok(self.unifier.add_ty(TypeEnum::TTuple { ty }))
+    }
+
+    fn infer_attribute(&mut self, value: &ast::Expr<Option<Type>>, attr: &str) -> InferenceResult {
+        let (attr_ty, _) = self.unifier.get_fresh_var();
+        let fields = once((attr.to_string(), attr_ty)).collect();
+        let record = self.unifier.add_record(fields);
+        self.constrain(value.custom.unwrap(), record)?;
+        Ok(attr_ty)
+    }
+
+    fn infer_bool_ops(&mut self, values: &[ast::Expr<Option<Type>>]) -> InferenceResult {
+        let b = self.primitives.bool;
+        for v in values {
+            self.constrain(v.custom.unwrap(), b)?;
+        }
+        Ok(b)
+    }
+
+    fn infer_bin_ops(
+        &mut self,
+        left: &ast::Expr<Option<Type>>,
+        op: &ast::Operator,
+        right: &ast::Expr<Option<Type>>,
+    ) -> InferenceResult {
+        let method = binop_name(op);
+        let ret = self.unifier.get_fresh_var().0;
+        self.build_method_call(
+            left.location,
+            method.to_string(),
+            left.custom.unwrap(),
+            vec![right.custom.unwrap()],
+            ret,
+        )
+    }
+
+    fn infer_unary_ops(
+        &mut self,
+        op: &ast::Unaryop,
+        operand: &ast::Expr<Option<Type>>,
+    ) -> InferenceResult {
+        let method = unaryop_name(op);
+        let ret = self.unifier.get_fresh_var().0;
+        self.build_method_call(
+            operand.location,
+            method.to_string(),
+            operand.custom.unwrap(),
+            vec![],
+            ret,
+        )
+    }
+
+    fn infer_compare(
+        &mut self,
+        left: &ast::Expr<Option<Type>>,
+        ops: &[ast::Cmpop],
+        comparators: &[ast::Expr<Option<Type>>],
+    ) -> InferenceResult {
+        let boolean = self.primitives.bool;
+        for (a, b, c) in izip!(once(left).chain(comparators), comparators, ops) {
+            let method =
+                comparison_name(c).ok_or_else(|| "unsupported comparator".to_string())?.to_string();
+            self.build_method_call(
+                a.location,
+                method,
+                a.custom.unwrap(),
+                vec![b.custom.unwrap()],
+                boolean,
+            )?;
+        }
+        Ok(boolean)
+    }
+
+    fn infer_subscript(
+        &mut self,
+        value: &ast::Expr<Option<Type>>,
+        slice: &ast::Expr<Option<Type>>,
+    ) -> InferenceResult {
+        let ty = self.unifier.get_fresh_var().0;
+        match &slice.node {
+            ast::ExprKind::Slice { lower, upper, step } => {
+                for v in [lower.as_ref(), upper.as_ref(), step.as_ref()].iter().flatten() {
+                    self.constrain(v.custom.unwrap(), self.primitives.int32)?;
+                }
+                let list = self.unifier.add_ty(TypeEnum::TList { ty });
+                self.constrain(value.custom.unwrap(), list)?;
+                Ok(list)
+            }
+            ast::ExprKind::Constant { value: ast::Constant::Int(val), .. } => {
+                // the index is a constant, so value can be a sequence.
+                let ind: i32 = val.try_into().map_err(|_| "Index must be int32".to_string())?;
+                let map = once((ind, ty)).collect();
+                let seq = self.unifier.add_sequence(map);
+                self.constrain(value.custom.unwrap(), seq)?;
+                Ok(ty)
+            }
+            _ => {
+                // the index is not a constant, so value can only be a list
+                self.constrain(slice.custom.unwrap(), self.primitives.int32)?;
+                let list = self.unifier.add_ty(TypeEnum::TList { ty });
+                self.constrain(value.custom.unwrap(), list)?;
+                Ok(ty)
+            }
+        }
+    }
+
+    fn infer_if_expr(
+        &mut self,
+        test: &ast::Expr<Option<Type>>,
+        body: &ast::Expr<Option<Type>>,
+        orelse: &ast::Expr<Option<Type>>,
+    ) -> InferenceResult {
+        self.constrain(test.custom.unwrap(), self.primitives.bool)?;
+        let ty = self.unifier.get_fresh_var().0;
+        self.constrain(body.custom.unwrap(), ty)?;
+        self.constrain(orelse.custom.unwrap(), ty)?;
+        Ok(ty)
+    }
+}

nac3core/src/typecheck/type_inferencer/test.rs

@@ -0,0 +1,546 @@
+use super::super::typedef::*;
+use super::*;
+use crate::symbol_resolver::*;
+use crate::top_level::DefinitionId;
+use crate::{location::Location, top_level::TopLevelDef};
+use indoc::indoc;
+use itertools::zip;
+use parking_lot::RwLock;
+use rustpython_parser::parser::parse_program;
+use test_case::test_case;
+
+struct Resolver {
+    id_to_type: HashMap<String, Type>,
+    id_to_def: HashMap<String, DefinitionId>,
+    class_names: HashMap<String, Type>,
+}
+
+impl SymbolResolver for Resolver {
+    fn get_symbol_type(&self, _: &mut Unifier, _: &PrimitiveStore, str: &str) -> Option<Type> {
+        self.id_to_type.get(str).cloned()
+    }
+
+    fn get_symbol_value(&self, _: &str) -> Option<SymbolValue> {
+        unimplemented!()
+    }
+
+    fn get_symbol_location(&self, _: &str) -> Option<Location> {
+        unimplemented!()
+    }
+
+    fn get_identifier_def(&self, id: &str) -> Option<DefinitionId> {
+        self.id_to_def.get(id).cloned()
+    }
+}
+
+struct TestEnvironment {
+    pub unifier: Unifier,
+    pub function_data: FunctionData,
+    pub primitives: PrimitiveStore,
+    pub id_to_name: HashMap<usize, String>,
+    pub identifier_mapping: HashMap<String, Type>,
+    pub virtual_checks: Vec<(Type, Type)>,
+    pub calls: HashMap<CodeLocation, CallId>,
+    pub top_level: TopLevelContext,
+}
+
+impl TestEnvironment {
+    pub fn basic_test_env() -> TestEnvironment {
+        let mut unifier = Unifier::new();
+
+        let int32 = unifier.add_ty(TypeEnum::TObj {
+            obj_id: DefinitionId(0),
+            fields: HashMap::new().into(),
+            params: HashMap::new().into(),
+        });
+        let int64 = unifier.add_ty(TypeEnum::TObj {
+            obj_id: DefinitionId(1),
+            fields: HashMap::new().into(),
+            params: HashMap::new().into(),
+        });
+        let float = unifier.add_ty(TypeEnum::TObj {
+            obj_id: DefinitionId(2),
+            fields: HashMap::new().into(),
+            params: HashMap::new().into(),
+        });
+        let bool = unifier.add_ty(TypeEnum::TObj {
+            obj_id: DefinitionId(3),
+            fields: HashMap::new().into(),
+            params: HashMap::new().into(),
+        });
+        let none = unifier.add_ty(TypeEnum::TObj {
+            obj_id: DefinitionId(4),
+            fields: HashMap::new().into(),
+            params: HashMap::new().into(),
+        });
+        let primitives = PrimitiveStore { int32, int64, float, bool, none };
+        set_primitives_magic_methods(&primitives, &mut unifier);
+
+        let id_to_name = [
+            (0, "int32".to_string()),
+            (1, "int64".to_string()),
+            (2, "float".to_string()),
+            (3, "bool".to_string()),
+            (4, "none".to_string()),
+        ]
+        .iter()
+        .cloned()
+        .collect();
+
+        let mut identifier_mapping = HashMap::new();
+        identifier_mapping.insert("None".into(), none);
+
+        let resolver = Arc::new(Resolver {
+            id_to_type: identifier_mapping.clone(),
+            id_to_def: Default::default(),
+            class_names: Default::default(),
+        }) as Arc<dyn SymbolResolver + Send + Sync>;
+
+        TestEnvironment {
+            top_level: TopLevelContext {
+                definitions: Default::default(),
+                unifiers: Default::default(),
+            },
+            unifier,
+            function_data: FunctionData {
+                resolver,
+                bound_variables: Vec::new(),
+                return_type: None,
+            },
+            primitives,
+            id_to_name,
+            identifier_mapping,
+            virtual_checks: Vec::new(),
+            calls: HashMap::new(),
+        }
+    }
+
+    fn new() -> TestEnvironment {
+        let mut unifier = Unifier::new();
+        let mut identifier_mapping = HashMap::new();
+        let mut top_level_defs: Vec<Arc<RwLock<TopLevelDef>>> = Vec::new();
+        let int32 = unifier.add_ty(TypeEnum::TObj {
+            obj_id: DefinitionId(0),
+            fields: HashMap::new().into(),
+            params: HashMap::new().into(),
+        });
+        let int64 = unifier.add_ty(TypeEnum::TObj {
+            obj_id: DefinitionId(1),
+            fields: HashMap::new().into(),
+            params: HashMap::new().into(),
+        });
+        let float = unifier.add_ty(TypeEnum::TObj {
+            obj_id: DefinitionId(2),
+            fields: HashMap::new().into(),
+            params: HashMap::new().into(),
+        });
+        let bool = unifier.add_ty(TypeEnum::TObj {
+            obj_id: DefinitionId(3),
+            fields: HashMap::new().into(),
+            params: HashMap::new().into(),
+        });
+        let none = unifier.add_ty(TypeEnum::TObj {
+            obj_id: DefinitionId(4),
+            fields: HashMap::new().into(),
+            params: HashMap::new().into(),
+        });
+        identifier_mapping.insert("None".into(), none);
+        for i in 0..5 {
+            top_level_defs.push(
+                RwLock::new(TopLevelDef::Class {
+                    object_id: DefinitionId(i),
+                    type_vars: Default::default(),
+                    fields: Default::default(),
+                    methods: Default::default(),
+                    ancestors: Default::default(),
+                    resolver: None,
+                })
+                .into(),
+            );
+        }
+
+        let primitives = PrimitiveStore { int32, int64, float, bool, none };
+
+        let (v0, id) = unifier.get_fresh_var();
+
+        let foo_ty = unifier.add_ty(TypeEnum::TObj {
+            obj_id: DefinitionId(5),
+            fields: [("a".into(), v0)].iter().cloned().collect::<HashMap<_, _>>().into(),
+            params: [(id, v0)].iter().cloned().collect::<HashMap<_, _>>().into(),
+        });
+        top_level_defs.push(
+            RwLock::new(TopLevelDef::Class {
+                object_id: DefinitionId(5),
+                type_vars: vec![v0],
+                fields: [("a".into(), v0)].into(),
+                methods: Default::default(),
+                ancestors: Default::default(),
+                resolver: None,
+            })
+            .into(),
+        );
+
+        identifier_mapping.insert(
+            "Foo".into(),
+            unifier.add_ty(TypeEnum::TFunc(
+                FunSignature {
+                    args: vec![],
+                    ret: foo_ty,
+                    vars: [(id, v0)].iter().cloned().collect(),
+                }
+                .into(),
+            )),
+        );
+
+        let fun = unifier.add_ty(TypeEnum::TFunc(
+            FunSignature { args: vec![], ret: int32, vars: Default::default() }.into(),
+        ));
+        let bar = unifier.add_ty(TypeEnum::TObj {
+            obj_id: DefinitionId(6),
+            fields: [("a".into(), int32), ("b".into(), fun)]
+                .iter()
+                .cloned()
+                .collect::<HashMap<_, _>>()
+                .into(),
+            params: Default::default(),
+        });
+        top_level_defs.push(
+            RwLock::new(TopLevelDef::Class {
+                object_id: DefinitionId(6),
+                type_vars: Default::default(),
+                fields: [("a".into(), int32), ("b".into(), fun)].into(),
+                methods: Default::default(),
+                ancestors: Default::default(),
+                resolver: None,
+            })
+            .into(),
+        );
+        identifier_mapping.insert(
+            "Bar".into(),
+            unifier.add_ty(TypeEnum::TFunc(
+                FunSignature { args: vec![], ret: bar, vars: Default::default() }.into(),
+            )),
+        );
+
+        let bar2 = unifier.add_ty(TypeEnum::TObj {
+            obj_id: DefinitionId(7),
+            fields: [("a".into(), bool), ("b".into(), fun)]
+                .iter()
+                .cloned()
+                .collect::<HashMap<_, _>>()
+                .into(),
+            params: Default::default(),
+        });
+        top_level_defs.push(
+            RwLock::new(TopLevelDef::Class {
+                object_id: DefinitionId(7),
+                type_vars: Default::default(),
+                fields: [("a".into(), bool), ("b".into(), fun)].into(),
+                methods: Default::default(),
+                ancestors: Default::default(),
+                resolver: None,
+            })
+            .into(),
+        );
+        identifier_mapping.insert(
+            "Bar2".into(),
+            unifier.add_ty(TypeEnum::TFunc(
+                FunSignature { args: vec![], ret: bar2, vars: Default::default() }.into(),
+            )),
+        );
+        let class_names = [("Bar".into(), bar), ("Bar2".into(), bar2)].iter().cloned().collect();
+
+        let id_to_name = [
+            (0, "int32".to_string()),
+            (1, "int64".to_string()),
+            (2, "float".to_string()),
+            (3, "bool".to_string()),
+            (4, "none".to_string()),
+            (5, "Foo".to_string()),
+            (6, "Bar".to_string()),
+            (7, "Bar2".to_string()),
+        ]
+        .iter()
+        .cloned()
+        .collect();
+
+        let top_level = TopLevelContext {
+            definitions: Arc::new(RwLock::new(top_level_defs)),
+            unifiers: Default::default(),
+        };
+
+        let resolver = Arc::new(Resolver {
+            id_to_type: identifier_mapping.clone(),
+            id_to_def: [
+                ("Foo".into(), DefinitionId(5)),
+                ("Bar".into(), DefinitionId(6)),
+                ("Bar2".into(), DefinitionId(7)),
+            ]
+            .iter()
+            .cloned()
+            .collect(),
+            class_names,
+        }) as Arc<dyn SymbolResolver + Send + Sync>;
+
+        TestEnvironment {
+            unifier,
+            top_level,
+            function_data: FunctionData {
+                resolver,
+                bound_variables: Vec::new(),
+                return_type: None,
+            },
+            primitives,
+            id_to_name,
+            identifier_mapping,
+            virtual_checks: Vec::new(),
+            calls: HashMap::new(),
+        }
+    }
+
+    fn get_inferencer(&mut self) -> Inferencer {
+        Inferencer {
+            top_level: &self.top_level,
+            function_data: &mut self.function_data,
+            unifier: &mut self.unifier,
+            variable_mapping: Default::default(),
+            primitives: &mut self.primitives,
+            virtual_checks: &mut self.virtual_checks,
+            calls: &mut self.calls,
+        }
+    }
+}
+
+#[test_case(indoc! {"
+        a = 1234
+        b = int64(2147483648)
+        c = 1.234
+        d = True
+    "},
+    [("a", "int32"), ("b", "int64"), ("c", "float"), ("d", "bool")].iter().cloned().collect(),
+    &[]
+    ; "primitives test")]
+#[test_case(indoc! {"
+        a = lambda x, y: x
+        b = lambda x: a(x, x)
+        c = 1.234
+        d = b(c)
+    "},
+    [("a", "fn[[x=float, y=float], float]"), ("b", "fn[[x=float], float]"), ("c", "float"), ("d", "float")].iter().cloned().collect(),
+    &[]
+    ; "lambda test")]
+#[test_case(indoc! {"
+        a = lambda x: x
+        b = lambda x: x
+
+        foo1 = Foo()
+        foo2 = Foo()
+        c = a(foo1.a)
+        d = b(foo2.a)
+
+        a(True)
+        b(123)
+
+    "},
+    [("a", "fn[[x=bool], bool]"), ("b", "fn[[x=int32], int32]"), ("c", "bool"),
+     ("d", "int32"), ("foo1", "Foo[bool]"), ("foo2", "Foo[int32]")].iter().cloned().collect(),
+    &[]
+    ; "obj test")]
+#[test_case(indoc! {"
+        f = lambda x: True
+        a = [1, 2, 3]
+        b = [f(x) for x in a if f(x)]
+    "},
+    [("a", "list[int32]"), ("b", "list[bool]"), ("f", "fn[[x=int32], bool]")].iter().cloned().collect(),
+    &[]
+    ; "listcomp test")]
+#[test_case(indoc! {"
+        a = virtual(Bar(), Bar)
+        b = a.b()
+        a = virtual(Bar2())
+    "},
+    [("a", "virtual[Bar]"), ("b", "int32")].iter().cloned().collect(),
+    &[("Bar", "Bar"), ("Bar2", "Bar")]
+    ; "virtual test")]
+#[test_case(indoc! {"
+        a = [virtual(Bar(), Bar), virtual(Bar2())]
+        b = [x.b() for x in a]
+    "},
+    [("a", "list[virtual[Bar]]"), ("b", "list[int32]")].iter().cloned().collect(),
+    &[("Bar", "Bar"), ("Bar2", "Bar")]
+    ; "virtual list test")]
+fn test_basic(source: &str, mapping: HashMap<&str, &str>, virtuals: &[(&str, &str)]) {
+    println!("source:\n{}", source);
+    let mut env = TestEnvironment::new();
+    let id_to_name = std::mem::take(&mut env.id_to_name);
+    let mut defined_identifiers: Vec<_> = env.identifier_mapping.keys().cloned().collect();
+    defined_identifiers.push("virtual".to_string());
+    let mut inferencer = env.get_inferencer();
+    let statements = parse_program(source).unwrap();
+    let statements = statements
+        .into_iter()
+        .map(|v| inferencer.fold_stmt(v))
+        .collect::<Result<Vec<_>, _>>()
+        .unwrap();
+
+    inferencer.check_block(&statements, &mut defined_identifiers).unwrap();
+
+    for (k, v) in inferencer.variable_mapping.iter() {
+        let name = inferencer.unifier.stringify(
+            *v,
+            &mut |v| id_to_name.get(&v).unwrap().clone(),
+            &mut |v| format!("v{}", v),
+        );
+        println!("{}: {}", k, name);
+    }
+    for (k, v) in mapping.iter() {
+        let ty = inferencer.variable_mapping.get(*k).unwrap();
+        let name = inferencer.unifier.stringify(
+            *ty,
+            &mut |v| id_to_name.get(&v).unwrap().clone(),
+            &mut |v| format!("v{}", v),
+        );
+        assert_eq!(format!("{}: {}", k, v), format!("{}: {}", k, name));
+    }
+    assert_eq!(inferencer.virtual_checks.len(), virtuals.len());
+    for ((a, b), (x, y)) in zip(inferencer.virtual_checks.iter(), virtuals) {
+        let a = inferencer.unifier.stringify(
+            *a,
+            &mut |v| id_to_name.get(&v).unwrap().clone(),
+            &mut |v| format!("v{}", v),
+        );
+        let b = inferencer.unifier.stringify(
+            *b,
+            &mut |v| id_to_name.get(&v).unwrap().clone(),
+            &mut |v| format!("v{}", v),
+        );
+
+        assert_eq!(&a, x);
+        assert_eq!(&b, y);
+    }
+}
+
+#[test_case(indoc! {"
+        a = 2
+        b = 2
+        c = a + b
+        d = a - b
+        e = a * b
+        f = a / b
+        g = a // b
+        h = a % b
+    "},
+    [("a", "int32"),
+    ("b", "int32"),
+    ("c", "int32"),
+    ("d", "int32"),
+    ("e", "int32"),
+    ("f", "float"),
+    ("g", "int32"),
+    ("h", "int32")].iter().cloned().collect()
+    ; "int32")]
+#[test_case(
+    indoc! {"
+        a = 2.4
+        b = 3.6
+        c = a + b
+        d = a - b
+        e = a * b
+        f = a / b
+        g = a // b
+        h = a % b
+        i = a ** b
+        ii = 3
+        j = a ** b
+    "},
+    [("a", "float"),
+    ("b", "float"),
+    ("c", "float"),
+    ("d", "float"),
+    ("e", "float"),
+    ("f", "float"),
+    ("g", "float"),
+    ("h", "float"),
+    ("i", "float"),
+    ("ii", "int32"),
+    ("j", "float")].iter().cloned().collect()
+    ; "float"
+)]
+#[test_case(
+    indoc! {"
+        a = int64(12312312312)
+        b = int64(24242424424)
+        c = a + b
+        d = a - b
+        e = a * b
+        f = a / b
+        g = a // b
+        h = a % b
+        i = a == b
+        j = a > b
+        k = a < b
+        l = a != b
+    "},
+    [("a", "int64"),
+    ("b", "int64"),
+    ("c", "int64"),
+    ("d", "int64"),
+    ("e", "int64"),
+    ("f", "float"),
+    ("g", "int64"),
+    ("h", "int64"),
+    ("i", "bool"),
+    ("j", "bool"),
+    ("k", "bool"),
+    ("l", "bool")].iter().cloned().collect()
+    ; "int64"
+)]
+#[test_case(
+    indoc! {"
+        a = True
+        b = False
+        c = a == b
+        d = not a
+        e = a != b
+    "},
+    [("a", "bool"),
+    ("b", "bool"),
+    ("c", "bool"),
+    ("d", "bool"),
+    ("e", "bool")].iter().cloned().collect()
+    ; "boolean"
+)]
+fn test_primitive_magic_methods(source: &str, mapping: HashMap<&str, &str>) {
+    println!("source:\n{}", source);
+    let mut env = TestEnvironment::basic_test_env();
+    let id_to_name = std::mem::take(&mut env.id_to_name);
+    let mut defined_identifiers: Vec<_> = env.identifier_mapping.keys().cloned().collect();
+    defined_identifiers.push("virtual".to_string());
+    let mut inferencer = env.get_inferencer();
+    let statements = parse_program(source).unwrap();
+    let statements = statements
+        .into_iter()
+        .map(|v| inferencer.fold_stmt(v))
+        .collect::<Result<Vec<_>, _>>()
+        .unwrap();
+
+    inferencer.check_block(&statements, &mut defined_identifiers).unwrap();
+
+    for (k, v) in inferencer.variable_mapping.iter() {
+        let name = inferencer.unifier.stringify(
+            *v,
+            &mut |v| id_to_name.get(&v).unwrap().clone(),
+            &mut |v| format!("v{}", v),
+        );
+        println!("{}: {}", k, name);
+    }
+    for (k, v) in mapping.iter() {
+        let ty = inferencer.variable_mapping.get(*k).unwrap();
+        let name = inferencer.unifier.stringify(
+            *ty,
+            &mut |v| id_to_name.get(&v).unwrap().clone(),
+            &mut |v| format!("v{}", v),
+        );
+        assert_eq!(format!("{}: {}", k, v), format!("{}: {}", k, name));
+    }
+}

nac3core/src/typecheck/typedef/mod.rs

@@ -0,0 +1,947 @@
+use itertools::{chain, zip, Itertools};
+use std::borrow::Cow;
+use std::cell::RefCell;
+use std::collections::HashMap;
+use std::iter::once;
+use std::rc::Rc;
+use std::sync::{Arc, Mutex};
+
+use super::unification_table::{UnificationKey, UnificationTable};
+use crate::symbol_resolver::SymbolValue;
+use crate::top_level::DefinitionId;
+
+#[cfg(test)]
+mod test;
+
+/// Handle for a type, implementated as a key in the unification table.
+pub type Type = UnificationKey;
+
+#[derive(Clone, Copy, PartialEq, Eq)]
+pub struct CallId(usize);
+
+pub type Mapping<K, V = Type> = HashMap<K, V>;
+type VarMap = Mapping<u32>;
+
+#[derive(Clone)]
+pub struct Call {
+    pub posargs: Vec<Type>,
+    pub kwargs: HashMap<String, Type>,
+    pub ret: Type,
+    pub fun: RefCell<Option<Type>>,
+}
+
+#[derive(Clone)]
+pub struct FuncArg {
+    pub name: String,
+    pub ty: Type,
+    pub default_value: Option<SymbolValue>,
+}
+
+#[derive(Clone)]
+pub struct FunSignature {
+    pub args: Vec<FuncArg>,
+    pub ret: Type,
+    pub vars: VarMap,
+}
+
+#[derive(Clone)]
+pub enum TypeVarMeta {
+    Generic,
+    Sequence(RefCell<Mapping<i32>>),
+    Record(RefCell<Mapping<String>>),
+}
+
+#[derive(Clone)]
+pub enum TypeEnum {
+    TRigidVar {
+        id: u32,
+    },
+    TVar {
+        id: u32,
+        meta: TypeVarMeta,
+        // empty indicates no restriction
+        range: RefCell<Vec<Type>>,
+    },
+    TTuple {
+        ty: Vec<Type>,
+    },
+    TList {
+        ty: Type,
+    },
+    TObj {
+        obj_id: DefinitionId,
+        fields: RefCell<Mapping<String>>,
+        params: RefCell<VarMap>,
+    },
+    TVirtual {
+        ty: Type,
+    },
+    TCall(RefCell<Vec<CallId>>),
+    TFunc(RefCell<FunSignature>),
+}
+
+impl TypeEnum {
+    pub fn get_type_name(&self) -> &'static str {
+        match self {
+            TypeEnum::TRigidVar { .. } => "TRigidVar",
+            TypeEnum::TVar { .. } => "TVar",
+            TypeEnum::TTuple { .. } => "TTuple",
+            TypeEnum::TList { .. } => "TList",
+            TypeEnum::TObj { .. } => "TObj",
+            TypeEnum::TVirtual { .. } => "TVirtual",
+            TypeEnum::TCall { .. } => "TCall",
+            TypeEnum::TFunc { .. } => "TFunc",
+        }
+    }
+}
+
+pub type SharedUnifier = Arc<Mutex<(UnificationTable<TypeEnum>, u32, Vec<Call>)>>;
+
+pub struct Unifier {
+    unification_table: UnificationTable<Rc<TypeEnum>>,
+    calls: Vec<Rc<Call>>,
+    var_id: u32,
+}
+
+impl Unifier {
+    /// Get an empty unifier
+    pub fn new() -> Unifier {
+        Unifier { unification_table: UnificationTable::new(), var_id: 0, calls: Vec::new() }
+    }
+
+    /// Determine if the two types are the same
+    pub fn unioned(&mut self, a: Type, b: Type) -> bool {
+        self.unification_table.unioned(a, b)
+    }
+
+    pub fn from_shared_unifier(unifier: &SharedUnifier) -> Unifier {
+        let lock = unifier.lock().unwrap();
+        Unifier {
+            unification_table: UnificationTable::from_send(&lock.0),
+            var_id: lock.1,
+            calls: lock.2.iter().map(|v| Rc::new(v.clone())).collect_vec(),
+        }
+    }
+
+    pub fn get_shared_unifier(&self) -> SharedUnifier {
+        Arc::new(Mutex::new((
+            self.unification_table.get_send(),
+            self.var_id,
+            self.calls.iter().map(|v| v.as_ref().clone()).collect_vec(),
+        )))
+    }
+
+    /// Register a type to the unifier.
+    /// Returns a key in the unification_table.
+    pub fn add_ty(&mut self, a: TypeEnum) -> Type {
+        self.unification_table.new_key(Rc::new(a))
+    }
+
+    pub fn add_record(&mut self, fields: Mapping<String>) -> Type {
+        let id = self.var_id + 1;
+        self.var_id += 1;
+        self.add_ty(TypeEnum::TVar {
+            id,
+            range: vec![].into(),
+            meta: TypeVarMeta::Record(fields.into()),
+        })
+    }
+
+    pub fn add_call(&mut self, call: Call) -> CallId {
+        let id = CallId(self.calls.len());
+        self.calls.push(Rc::new(call));
+        id
+    }
+
+    pub fn get_representative(&mut self, ty: Type) -> Type {
+        self.unification_table.get_representative(ty)
+    }
+
+    pub fn add_sequence(&mut self, sequence: Mapping<i32>) -> Type {
+        let id = self.var_id + 1;
+        self.var_id += 1;
+        self.add_ty(TypeEnum::TVar {
+            id,
+            range: vec![].into(),
+            meta: TypeVarMeta::Sequence(sequence.into()),
+        })
+    }
+
+    /// Get the TypeEnum of a type.
+    pub fn get_ty(&mut self, a: Type) -> Rc<TypeEnum> {
+        self.unification_table.probe_value(a).clone()
+    }
+
+    pub fn get_fresh_rigid_var(&mut self) -> (Type, u32) {
+        let id = self.var_id + 1;
+        self.var_id += 1;
+        (self.add_ty(TypeEnum::TRigidVar { id }), id)
+    }
+
+    pub fn get_fresh_var(&mut self) -> (Type, u32) {
+        self.get_fresh_var_with_range(&[])
+    }
+
+    /// Get a fresh type variable.
+    pub fn get_fresh_var_with_range(&mut self, range: &[Type]) -> (Type, u32) {
+        let id = self.var_id + 1;
+        self.var_id += 1;
+        let range = range.to_vec().into();
+        (self.add_ty(TypeEnum::TVar { id, range, meta: TypeVarMeta::Generic }), id)
+    }
+
+    /// Unification would not unify rigid variables with other types, but we want to do this for
+    /// function instantiations, so we make it explicit.
+    pub fn replace_rigid_var(&mut self, rigid: Type, b: Type) {
+        assert!(matches!(&*self.get_ty(rigid), TypeEnum::TRigidVar { .. }));
+        self.set_a_to_b(rigid, b);
+    }
+
+    pub fn get_instantiations(&mut self, ty: Type) -> Option<Vec<Type>> {
+        match &*self.get_ty(ty) {
+            TypeEnum::TVar { range, .. } => {
+                let range = range.borrow();
+                if range.is_empty() {
+                    None
+                } else {
+                    Some(
+                        range
+                            .iter()
+                            .map(|ty| self.get_instantiations(*ty).unwrap_or_else(|| vec![*ty]))
+                            .flatten()
+                            .collect_vec(),
+                    )
+                }
+            }
+            TypeEnum::TList { ty } => self
+                .get_instantiations(*ty)
+                .map(|ty| ty.iter().map(|&ty| self.add_ty(TypeEnum::TList { ty })).collect_vec()),
+            TypeEnum::TVirtual { ty } => self.get_instantiations(*ty).map(|ty| {
+                ty.iter().map(|&ty| self.add_ty(TypeEnum::TVirtual { ty })).collect_vec()
+            }),
+            TypeEnum::TTuple { ty } => {
+                let tuples = ty
+                    .iter()
+                    .map(|ty| self.get_instantiations(*ty).unwrap_or_else(|| vec![*ty]))
+                    .multi_cartesian_product()
+                    .collect_vec();
+                if tuples.len() == 1 {
+                    None
+                } else {
+                    Some(
+                        tuples.into_iter().map(|ty| self.add_ty(TypeEnum::TTuple { ty })).collect(),
+                    )
+                }
+            }
+            TypeEnum::TObj { params, .. } => {
+                let params = params.borrow();
+                let (keys, params): (Vec<&u32>, Vec<&Type>) = params.iter().unzip();
+                let params = params
+                    .into_iter()
+                    .map(|ty| self.get_instantiations(*ty).unwrap_or_else(|| vec![*ty]))
+                    .multi_cartesian_product()
+                    .collect_vec();
+                if params.len() <= 1 {
+                    None
+                } else {
+                    Some(
+                        params
+                            .into_iter()
+                            .map(|params| {
+                                self.subst(
+                                    ty,
+                                    &zip(keys.iter().cloned().cloned(), params.iter().cloned())
+                                        .collect(),
+                                )
+                                .unwrap_or(ty)
+                            })
+                            .collect(),
+                    )
+                }
+            }
+            _ => None,
+        }
+    }
+
+    pub fn is_concrete(&mut self, a: Type, allowed_typevars: &[Type]) -> bool {
+        use TypeEnum::*;
+        match &*self.get_ty(a) {
+            TRigidVar { .. } => true,
+            TVar { .. } => allowed_typevars.iter().any(|b| self.unification_table.unioned(a, *b)),
+            TCall { .. } => false,
+            TList { ty } => self.is_concrete(*ty, allowed_typevars),
+            TTuple { ty } => ty.iter().all(|ty| self.is_concrete(*ty, allowed_typevars)),
+            TObj { params: vars, .. } => {
+                vars.borrow().values().all(|ty| self.is_concrete(*ty, allowed_typevars))
+            }
+            // functions are instantiated for each call sites, so the function type can contain
+            // type variables.
+            TFunc { .. } => true,
+            TVirtual { ty } => self.is_concrete(*ty, allowed_typevars),
+        }
+    }
+
+    pub fn unify(&mut self, a: Type, b: Type) -> Result<(), String> {
+        if self.unification_table.unioned(a, b) {
+            Ok(())
+        } else {
+            self.unify_impl(a, b, false)
+        }
+    }
+
+    fn unify_impl(&mut self, a: Type, b: Type, swapped: bool) -> Result<(), String> {
+        use TypeEnum::*;
+        use TypeVarMeta::*;
+        let (ty_a, ty_b) = {
+            (
+                self.unification_table.probe_value(a).clone(),
+                self.unification_table.probe_value(b).clone(),
+            )
+        };
+        match (&*ty_a, &*ty_b) {
+            (TVar { meta: meta1, range: range1, .. }, TVar { meta: meta2, range: range2, .. }) => {
+                self.occur_check(a, b)?;
+                self.occur_check(b, a)?;
+                match (meta1, meta2) {
+                    (Generic, _) => {}
+                    (_, Generic) => {
+                        return self.unify_impl(b, a, true);
+                    }
+                    (Record(fields1), Record(fields2)) => {
+                        let mut fields2 = fields2.borrow_mut();
+                        for (key, value) in fields1.borrow().iter() {
+                            if let Some(ty) = fields2.get(key) {
+                                self.unify(*ty, *value)?;
+                            } else {
+                                fields2.insert(key.clone(), *value);
+                            }
+                        }
+                    }
+                    (Sequence(map1), Sequence(map2)) => {
+                        let mut map2 = map2.borrow_mut();
+                        for (key, value) in map1.borrow().iter() {
+                            if let Some(ty) = map2.get(key) {
+                                self.unify(*ty, *value)?;
+                            } else {
+                                map2.insert(*key, *value);
+                            }
+                        }
+                    }
+                    _ => {
+                        return Err("Incompatible".to_string());
+                    }
+                }
+                let range1 = range1.borrow();
+                // new range is the intersection of them
+                // empty range indicates no constraint
+                if !range1.is_empty() {
+                    let old_range2 = range2.take();
+                    let mut range2 = range2.borrow_mut();
+                    if old_range2.is_empty() {
+                        range2.extend_from_slice(&range1);
+                    }
+                    for v1 in old_range2.iter() {
+                        for v2 in range1.iter() {
+                            if let Ok(result) = self.get_intersection(*v1, *v2) {
+                                range2.push(result.unwrap_or(*v2));
+                            }
+                        }
+                    }
+                    if range2.is_empty() {
+                        return Err(
+                            "cannot unify type variables with incompatible value range".to_string()
+                        );
+                    }
+                }
+                self.set_a_to_b(a, b);
+            }
+            (TVar { meta: Generic, id, range, .. }, _) => {
+                self.occur_check(a, b)?;
+                // We check for the range of the type variable to see if unification is allowed.
+                // Note that although b may be compatible with a, we may have to constrain type
+                // variables in b to make sure that instantiations of b would always be compatible
+                // with a.
+                // The return value x of check_var_compatibility would be a new type that is
+                // guaranteed to be compatible with a under all possible instantiations. So we
+                // unify x with b to recursively apply the constrains, and then set a to x.
+                let x = self.check_var_compatibility(*id, b, &range.borrow())?.unwrap_or(b);
+                self.unify(x, b)?;
+                self.set_a_to_b(a, x);
+            }
+            (TVar { meta: Sequence(map), id, range, .. }, TTuple { ty }) => {
+                self.occur_check(a, b)?;
+                let len = ty.len() as i32;
+                for (k, v) in map.borrow().iter() {
+                    // handle negative index
+                    let ind = if *k < 0 { len + *k } else { *k };
+                    if ind >= len || ind < 0 {
+                        return Err(format!(
+                            "Tuple index out of range. (Length: {}, Index: {})",
+                            len, k
+                        ));
+                    }
+                    self.unify(*v, ty[ind as usize])?;
+                }
+                let x = self.check_var_compatibility(*id, b, &range.borrow())?.unwrap_or(b);
+                self.unify(x, b)?;
+                self.set_a_to_b(a, x);
+            }
+            (TVar { meta: Sequence(map), id, range, .. }, TList { ty }) => {
+                self.occur_check(a, b)?;
+                for v in map.borrow().values() {
+                    self.unify(*v, *ty)?;
+                }
+                let x = self.check_var_compatibility(*id, b, &range.borrow())?.unwrap_or(b);
+                self.unify(x, b)?;
+                self.set_a_to_b(a, x);
+            }
+            (TTuple { ty: ty1 }, TTuple { ty: ty2 }) => {
+                if ty1.len() != ty2.len() {
+                    return Err(format!(
+                        "Cannot unify tuples with length {} and {}",
+                        ty1.len(),
+                        ty2.len()
+                    ));
+                }
+                for (x, y) in ty1.iter().zip(ty2.iter()) {
+                    self.unify(*x, *y)?;
+                }
+                self.set_a_to_b(a, b);
+            }
+            (TList { ty: ty1 }, TList { ty: ty2 }) => {
+                self.unify(*ty1, *ty2)?;
+                self.set_a_to_b(a, b);
+            }
+            (TVar { meta: Record(map), id, range, .. }, TObj { fields, .. }) => {
+                self.occur_check(a, b)?;
+                for (k, v) in map.borrow().iter() {
+                    let ty = fields
+                        .borrow()
+                        .get(k)
+                        .copied()
+                        .ok_or_else(|| format!("No such attribute {}", k))?;
+                    self.unify(ty, *v)?;
+                }
+                let x = self.check_var_compatibility(*id, b, &range.borrow())?.unwrap_or(b);
+                self.unify(x, b)?;
+                self.set_a_to_b(a, x);
+            }
+            (TVar { meta: Record(map), id, range, .. }, TVirtual { ty }) => {
+                self.occur_check(a, b)?;
+                let ty = self.get_ty(*ty);
+                if let TObj { fields, .. } = ty.as_ref() {
+                    for (k, v) in map.borrow().iter() {
+                        let ty = fields
+                            .borrow()
+                            .get(k)
+                            .copied()
+                            .ok_or_else(|| format!("No such attribute {}", k))?;
+                        if !matches!(self.get_ty(ty).as_ref(), TFunc { .. }) {
+                            return Err(format!("Cannot access field {} for virtual type", k));
+                        }
+                        self.unify(*v, ty)?;
+                    }
+                } else {
+                    // require annotation...
+                    return Err("Requires type annotation for virtual".to_string());
+                }
+                let x = self.check_var_compatibility(*id, b, &range.borrow())?.unwrap_or(b);
+                self.unify(x, b)?;
+                self.set_a_to_b(a, x);
+            }
+            (
+                TObj { obj_id: id1, params: params1, .. },
+                TObj { obj_id: id2, params: params2, .. },
+            ) => {
+                if id1 != id2 {
+                    return Err(format!("Cannot unify objects with ID {} and {}", id1.0, id2.0));
+                }
+                for (x, y) in zip(params1.borrow().values(), params2.borrow().values()) {
+                    self.unify(*x, *y)?;
+                }
+                self.set_a_to_b(a, b);
+            }
+            (TVirtual { ty: ty1 }, TVirtual { ty: ty2 }) => {
+                self.unify(*ty1, *ty2)?;
+                self.set_a_to_b(a, b);
+            }
+            (TCall(calls1), TCall(calls2)) => {
+                // we do not unify individual calls, instead we defer until the unification wtih a
+                // function definition.
+                calls2.borrow_mut().extend_from_slice(&calls1.borrow());
+            }
+            (TCall(calls), TFunc(signature)) => {
+                self.occur_check(a, b)?;
+                let required: Vec<String> = signature
+                    .borrow()
+                    .args
+                    .iter()
+                    .filter(|v| v.default_value.is_none())
+                    .map(|v| v.name.clone())
+                    .rev()
+                    .collect();
+                // we unify every calls to the function signature.
+                for c in calls.borrow().iter() {
+                    let Call { posargs, kwargs, ret, fun } = &*self.calls[c.0].clone();
+                    let instantiated = self.instantiate_fun(b, &*signature.borrow());
+                    let r = self.get_ty(instantiated);
+                    let r = r.as_ref();
+                    let signature;
+                    if let TypeEnum::TFunc(s) = &*r {
+                        signature = s;
+                    } else {
+                        unreachable!();
+                    }
+                    // we check to make sure that all required arguments (those without default
+                    // arguments) are provided, and do not provide the same argument twice.
+                    let mut required = required.clone();
+                    let mut all_names: Vec<_> = signature
+                        .borrow()
+                        .args
+                        .iter()
+                        .map(|v| (v.name.clone(), v.ty))
+                        .rev()
+                        .collect();
+                    for (i, t) in posargs.iter().enumerate() {
+                        if signature.borrow().args.len() <= i {
+                            return Err("Too many arguments.".to_string());
+                        }
+                        if !required.is_empty() {
+                            required.pop();
+                        }
+                        self.unify(all_names.pop().unwrap().1, *t)?;
+                    }
+                    for (k, t) in kwargs.iter() {
+                        if let Some(i) = required.iter().position(|v| v == k) {
+                            required.remove(i);
+                        }
+                        let i = all_names
+                            .iter()
+                            .position(|v| &v.0 == k)
+                            .ok_or_else(|| format!("Unknown keyword argument {}", k))?;
+                        self.unify(all_names.remove(i).1, *t)?;
+                    }
+                    if !required.is_empty() {
+                        return Err("Expected more arguments".to_string());
+                    }
+                    self.unify(*ret, signature.borrow().ret)?;
+                    *fun.borrow_mut() = Some(instantiated);
+                }
+                self.set_a_to_b(a, b);
+            }
+            (TFunc(sign1), TFunc(sign2)) => {
+                let (sign1, sign2) = (&*sign1.borrow(), &*sign2.borrow());
+                if !sign1.vars.is_empty() || !sign2.vars.is_empty() {
+                    return Err("Polymorphic function pointer is prohibited.".to_string());
+                }
+                if sign1.args.len() != sign2.args.len() {
+                    return Err("Functions differ in number of parameters.".to_string());
+                }
+                for (x, y) in sign1.args.iter().zip(sign2.args.iter()) {
+                    if x.name != y.name {
+                        return Err("Functions differ in parameter names.".to_string());
+                    }
+                    if x.default_value != y.default_value {
+                        return Err("Functions differ in optional parameters.".to_string());
+                    }
+                    self.unify(x.ty, y.ty)?;
+                }
+                self.unify(sign1.ret, sign2.ret)?;
+                self.set_a_to_b(a, b);
+            }
+            _ => {
+                if swapped {
+                    return self.incompatible_types(&*ty_a, &*ty_b);
+                } else {
+                    self.unify_impl(b, a, true)?;
+                }
+            }
+        }
+        Ok(())
+    }
+
+    /// Get string representation of the type
+    pub fn stringify<F, G>(&mut self, ty: Type, obj_to_name: &mut F, var_to_name: &mut G) -> String
+    where
+        F: FnMut(usize) -> String,
+        G: FnMut(u32) -> String,
+    {
+        use TypeVarMeta::*;
+        let ty = self.unification_table.probe_value(ty).clone();
+        match ty.as_ref() {
+            TypeEnum::TRigidVar { id } => var_to_name(*id),
+            TypeEnum::TVar { id, meta: Generic, .. } => var_to_name(*id),
+            TypeEnum::TVar { meta: Sequence(map), .. } => {
+                let fields = map
+                    .borrow()
+                    .iter()
+                    .map(|(k, v)| format!("{}={}", k, self.stringify(*v, obj_to_name, var_to_name)))
+                    .join(", ");
+                format!("seq[{}]", fields)
+            }
+            TypeEnum::TVar { meta: Record(fields), .. } => {
+                let fields = fields
+                    .borrow()
+                    .iter()
+                    .map(|(k, v)| format!("{}={}", k, self.stringify(*v, obj_to_name, var_to_name)))
+                    .join(", ");
+                format!("record[{}]", fields)
+            }
+            TypeEnum::TTuple { ty } => {
+                let mut fields = ty.iter().map(|v| self.stringify(*v, obj_to_name, var_to_name));
+                format!("tuple[{}]", fields.join(", "))
+            }
+            TypeEnum::TList { ty } => {
+                format!("list[{}]", self.stringify(*ty, obj_to_name, var_to_name))
+            }
+            TypeEnum::TVirtual { ty } => {
+                format!("virtual[{}]", self.stringify(*ty, obj_to_name, var_to_name))
+            }
+            TypeEnum::TObj { obj_id, params, .. } => {
+                let name = obj_to_name(obj_id.0);
+                let params = params.borrow();
+                if !params.is_empty() {
+                    let mut params =
+                        params.values().map(|v| self.stringify(*v, obj_to_name, var_to_name));
+                    format!("{}[{}]", name, params.join(", "))
+                } else {
+                    name
+                }
+            }
+            TypeEnum::TCall { .. } => "call".to_owned(),
+            TypeEnum::TFunc(signature) => {
+                let params = signature
+                    .borrow()
+                    .args
+                    .iter()
+                    .map(|arg| {
+                        format!("{}={}", arg.name, self.stringify(arg.ty, obj_to_name, var_to_name))
+                    })
+                    .join(", ");
+                let ret = self.stringify(signature.borrow().ret, obj_to_name, var_to_name);
+                format!("fn[[{}], {}]", params, ret)
+            }
+        }
+    }
+
+    fn set_a_to_b(&mut self, a: Type, b: Type) {
+        // unify a and b together, and set the value to b's value.
+        let table = &mut self.unification_table;
+        let ty_b = table.probe_value(b).clone();
+        table.unify(a, b);
+        table.set_value(a, ty_b)
+    }
+
+    fn incompatible_types(&self, a: &TypeEnum, b: &TypeEnum) -> Result<(), String> {
+        Err(format!("Cannot unify {} with {}", a.get_type_name(), b.get_type_name()))
+    }
+
+    /// Instantiate a function if it hasn't been instantiated.
+    /// Returns Some(T) where T is the instantiated type.
+    /// Returns None if the function is already instantiated.
+    fn instantiate_fun(&mut self, ty: Type, fun: &FunSignature) -> Type {
+        let mut instantiated = false;
+        let mut vars = Vec::new();
+        for (k, v) in fun.vars.iter() {
+            if let TypeEnum::TVar { id, range, .. } =
+                self.unification_table.probe_value(*v).as_ref()
+            {
+                if k != id {
+                    instantiated = true;
+                    break;
+                }
+                // actually, if the first check succeeded, the function should be uninstatiated.
+                // The cloned values must be used and would not be wasted.
+                vars.push((*k, range.clone()));
+            } else {
+                instantiated = true;
+                break;
+            }
+        }
+        if instantiated {
+            ty
+        } else {
+            let mapping = vars
+                .into_iter()
+                .map(|(k, range)| (k, self.get_fresh_var_with_range(range.borrow().as_ref()).0))
+                .collect();
+            self.subst(ty, &mapping).unwrap_or(ty)
+        }
+    }
+
+    /// Substitute type variables within a type into other types.
+    /// If this returns Some(T), T would be the substituted type.
+    /// If this returns None, the result type would be the original type
+    /// (no substitution has to be done).
+    pub fn subst(&mut self, a: Type, mapping: &VarMap) -> Option<Type> {
+        use TypeVarMeta::*;
+        let ty = self.unification_table.probe_value(a).clone();
+        // this function would only be called when we instantiate functions.
+        // function type signature should ONLY contain concrete types and type
+        // variables, i.e. things like TRecord, TCall should not occur, and we
+        // should be safe to not implement the substitution for those variants.
+        match &*ty {
+            TypeEnum::TRigidVar { .. } => None,
+            TypeEnum::TVar { id, meta: Generic, .. } => mapping.get(&id).cloned(),
+            TypeEnum::TTuple { ty } => {
+                let mut new_ty = Cow::from(ty);
+                for (i, t) in ty.iter().enumerate() {
+                    if let Some(t1) = self.subst(*t, mapping) {
+                        new_ty.to_mut()[i] = t1;
+                    }
+                }
+                if matches!(new_ty, Cow::Owned(_)) {
+                    Some(self.add_ty(TypeEnum::TTuple { ty: new_ty.into_owned() }))
+                } else {
+                    None
+                }
+            }
+            TypeEnum::TList { ty } => {
+                self.subst(*ty, mapping).map(|t| self.add_ty(TypeEnum::TList { ty: t }))
+            }
+            TypeEnum::TVirtual { ty } => {
+                self.subst(*ty, mapping).map(|t| self.add_ty(TypeEnum::TVirtual { ty: t }))
+            }
+            TypeEnum::TObj { obj_id, fields, params } => {
+                // Type variables in field types must be present in the type parameter.
+                // If the mapping does not contain any type variables in the
+                // parameter list, we don't need to substitute the fields.
+                // This is also used to prevent infinite substitution...
+                let params = params.borrow();
+                let need_subst = params.values().any(|v| {
+                    let ty = self.unification_table.probe_value(*v);
+                    if let TypeEnum::TVar { id, .. } = ty.as_ref() {
+                        mapping.contains_key(&id)
+                    } else {
+                        false
+                    }
+                });
+                if need_subst {
+                    let obj_id = *obj_id;
+                    let params = self.subst_map(&params, mapping).unwrap_or_else(|| params.clone());
+                    let fields = self
+                        .subst_map(&fields.borrow(), mapping)
+                        .unwrap_or_else(|| fields.borrow().clone());
+                    Some(self.add_ty(TypeEnum::TObj {
+                        obj_id,
+                        params: params.into(),
+                        fields: fields.into(),
+                    }))
+                } else {
+                    None
+                }
+            }
+            TypeEnum::TFunc(sig) => {
+                let FunSignature { args, ret, vars: params } = &*sig.borrow();
+                let new_params = self.subst_map(params, mapping);
+                let new_ret = self.subst(*ret, mapping);
+                let mut new_args = Cow::from(args);
+                for (i, t) in args.iter().enumerate() {
+                    if let Some(t1) = self.subst(t.ty, mapping) {
+                        let mut t = t.clone();
+                        t.ty = t1;
+                        new_args.to_mut()[i] = t;
+                    }
+                }
+                if new_params.is_some() || new_ret.is_some() || matches!(new_args, Cow::Owned(..)) {
+                    let params = new_params.unwrap_or_else(|| params.clone());
+                    let ret = new_ret.unwrap_or_else(|| *ret);
+                    let args = new_args.into_owned();
+                    Some(
+                        self.add_ty(TypeEnum::TFunc(
+                            FunSignature { args, ret, vars: params }.into(),
+                        )),
+                    )
+                } else {
+                    None
+                }
+            }
+            _ => unimplemented!(),
+        }
+    }
+
+    fn subst_map<K>(&mut self, map: &Mapping<K>, mapping: &VarMap) -> Option<Mapping<K>>
+    where
+        K: std::hash::Hash + std::cmp::Eq + std::clone::Clone,
+    {
+        let mut map2 = None;
+        for (k, v) in map.iter() {
+            if let Some(v1) = self.subst(*v, mapping) {
+                if map2.is_none() {
+                    map2 = Some(map.clone());
+                }
+                *map2.as_mut().unwrap().get_mut(k).unwrap() = v1;
+            }
+        }
+        map2
+    }
+
+    fn occur_check(&mut self, a: Type, b: Type) -> Result<(), String> {
+        use TypeVarMeta::*;
+        if self.unification_table.unioned(a, b) {
+            return Err("Recursive type is prohibited.".to_owned());
+        }
+        let ty = self.unification_table.probe_value(b).clone();
+
+        match ty.as_ref() {
+            TypeEnum::TRigidVar { .. } | TypeEnum::TVar { meta: Generic, .. } => {}
+            TypeEnum::TVar { meta: Sequence(map), .. } => {
+                for t in map.borrow().values() {
+                    self.occur_check(a, *t)?;
+                }
+            }
+            TypeEnum::TVar { meta: Record(map), .. } => {
+                for t in map.borrow().values() {
+                    self.occur_check(a, *t)?;
+                }
+            }
+            TypeEnum::TCall(calls) => {
+                let call_store = self.calls.clone();
+                for t in calls
+                    .borrow()
+                    .iter()
+                    .map(|call| {
+                        let call = call_store[call.0].as_ref();
+                        chain!(call.posargs.iter(), call.kwargs.values(), once(&call.ret))
+                    })
+                    .flatten()
+                {
+                    self.occur_check(a, *t)?;
+                }
+            }
+            TypeEnum::TTuple { ty } => {
+                for t in ty.iter() {
+                    self.occur_check(a, *t)?;
+                }
+            }
+            TypeEnum::TList { ty } | TypeEnum::TVirtual { ty } => {
+                self.occur_check(a, *ty)?;
+            }
+            TypeEnum::TObj { params: map, .. } => {
+                for t in map.borrow().values() {
+                    self.occur_check(a, *t)?;
+                }
+            }
+            TypeEnum::TFunc(sig) => {
+                let FunSignature { args, ret, vars: params } = &*sig.borrow();
+                for t in chain!(args.iter().map(|v| &v.ty), params.values(), once(ret)) {
+                    self.occur_check(a, *t)?;
+                }
+            }
+        }
+        Ok(())
+    }
+
+    fn get_intersection(&mut self, a: Type, b: Type) -> Result<Option<Type>, ()> {
+        use TypeEnum::*;
+        let x = self.get_ty(a);
+        let y = self.get_ty(b);
+        match (x.as_ref(), y.as_ref()) {
+            (TVar { range: range1, .. }, TVar { meta, range: range2, .. }) => {
+                // we should restrict range2
+                let range1 = range1.borrow();
+                // new range is the intersection of them
+                // empty range indicates no constraint
+                if !range1.is_empty() {
+                    let range2 = range2.borrow();
+                    let mut range = Vec::new();
+                    if range2.is_empty() {
+                        range.extend_from_slice(&range1);
+                    }
+                    for v1 in range2.iter() {
+                        for v2 in range1.iter() {
+                            let result = self.get_intersection(*v1, *v2);
+                            if let Ok(result) = result {
+                                range.push(result.unwrap_or(*v2));
+                            }
+                        }
+                    }
+                    if range.is_empty() {
+                        Err(())
+                    } else {
+                        let id = self.var_id + 1;
+                        self.var_id += 1;
+                        let ty = TVar { id, meta: meta.clone(), range: range.into() };
+                        Ok(Some(self.unification_table.new_key(ty.into())))
+                    }
+                } else {
+                    Ok(Some(b))
+                }
+            }
+            (_, TVar { range, .. }) => {
+                // range should be restricted to the left hand side
+                let range = range.borrow();
+                if range.is_empty() {
+                    Ok(Some(a))
+                } else {
+                    for v in range.iter() {
+                        let result = self.get_intersection(a, *v);
+                        if let Ok(result) = result {
+                            return Ok(result.or(Some(a)));
+                        }
+                    }
+                    Err(())
+                }
+            }
+            (TVar { id, range, .. }, _) => {
+                self.check_var_compatibility(*id, b, &range.borrow()).or(Err(()))
+            }
+            (TTuple { ty: ty1 }, TTuple { ty: ty2 }) => {
+                if ty1.len() != ty2.len() {
+                    return Err(());
+                }
+                let mut need_new = false;
+                let mut ty = ty1.clone();
+                for (a, b) in zip(ty1.iter(), ty2.iter()) {
+                    let result = self.get_intersection(*a, *b)?;
+                    ty.push(result.unwrap_or(*a));
+                    if result.is_some() {
+                        need_new = true;
+                    }
+                }
+                if need_new {
+                    Ok(Some(self.add_ty(TTuple { ty })))
+                } else {
+                    Ok(None)
+                }
+            }
+            (TList { ty: ty1 }, TList { ty: ty2 }) => {
+                Ok(self.get_intersection(*ty1, *ty2)?.map(|ty| self.add_ty(TList { ty })))
+            }
+            (TVirtual { ty: ty1 }, TVirtual { ty: ty2 }) => {
+                Ok(self.get_intersection(*ty1, *ty2)?.map(|ty| self.add_ty(TVirtual { ty })))
+            }
+            (TObj { obj_id: id1, .. }, TObj { obj_id: id2, .. }) => {
+                if id1 == id2 {
+                    Ok(None)
+                } else {
+                    Err(())
+                }
+            }
+            // don't deal with function shape for now
+            _ => Err(()),
+        }
+    }
+
+    fn check_var_compatibility(
+        &mut self,
+        id: u32,
+        b: Type,
+        range: &[Type],
+    ) -> Result<Option<Type>, String> {
+        if range.is_empty() {
+            return Ok(None);
+        }
+        for t in range.iter() {
+            let result = self.get_intersection(*t, b);
+            if let Ok(result) = result {
+                return Ok(result);
+            }
+        }
+        return Err(format!(
+            "Cannot unify type variable {} with {} due to incompatible value range",
+            id,
+            self.get_ty(b).get_type_name()
+        ));
+    }
+}

nac3core/src/typecheck/typedef/test.rs

@@ -0,0 +1,534 @@
+use super::*;
+use indoc::indoc;
+use itertools::Itertools;
+use std::collections::HashMap;
+use test_case::test_case;
+
+impl Unifier {
+    /// Check whether two types are equal.
+    fn eq(&mut self, a: Type, b: Type) -> bool {
+        use TypeVarMeta::*;
+        if a == b {
+            return true;
+        }
+        let (ty_a, ty_b) = {
+            let table = &mut self.unification_table;
+            if table.unioned(a, b) {
+                return true;
+            }
+            (table.probe_value(a).clone(), table.probe_value(b).clone())
+        };
+
+        match (&*ty_a, &*ty_b) {
+            (
+                TypeEnum::TVar { meta: Generic, id: id1, .. },
+                TypeEnum::TVar { meta: Generic, id: id2, .. },
+            ) => id1 == id2,
+            (
+                TypeEnum::TVar { meta: Sequence(map1), .. },
+                TypeEnum::TVar { meta: Sequence(map2), .. },
+            ) => self.map_eq(&map1.borrow(), &map2.borrow()),
+            (TypeEnum::TTuple { ty: ty1 }, TypeEnum::TTuple { ty: ty2 }) => {
+                ty1.len() == ty2.len()
+                    && ty1.iter().zip(ty2.iter()).all(|(t1, t2)| self.eq(*t1, *t2))
+            }
+            (TypeEnum::TList { ty: ty1 }, TypeEnum::TList { ty: ty2 })
+            | (TypeEnum::TVirtual { ty: ty1 }, TypeEnum::TVirtual { ty: ty2 }) => {
+                self.eq(*ty1, *ty2)
+            }
+            (
+                TypeEnum::TVar { meta: Record(fields1), .. },
+                TypeEnum::TVar { meta: Record(fields2), .. },
+            ) => self.map_eq(&fields1.borrow(), &fields2.borrow()),
+            (
+                TypeEnum::TObj { obj_id: id1, params: params1, .. },
+                TypeEnum::TObj { obj_id: id2, params: params2, .. },
+            ) => id1 == id2 && self.map_eq(&params1.borrow(), &params2.borrow()),
+            // TCall and TFunc are not yet implemented
+            _ => false,
+        }
+    }
+
+    fn map_eq<K>(&mut self, map1: &Mapping<K>, map2: &Mapping<K>) -> bool
+    where
+        K: std::hash::Hash + std::cmp::Eq + std::clone::Clone,
+    {
+        if map1.len() != map2.len() {
+            return false;
+        }
+        for (k, v) in map1.iter() {
+            if !map2.get(k).map(|v1| self.eq(*v, *v1)).unwrap_or(false) {
+                return false;
+            }
+        }
+        true
+    }
+}
+
+struct TestEnvironment {
+    pub unifier: Unifier,
+    type_mapping: HashMap<String, Type>,
+}
+
+impl TestEnvironment {
+    fn new() -> TestEnvironment {
+        let mut unifier = Unifier::new();
+        let mut type_mapping = HashMap::new();
+
+        type_mapping.insert(
+            "int".into(),
+            unifier.add_ty(TypeEnum::TObj {
+                obj_id: DefinitionId(0),
+                fields: HashMap::new().into(),
+                params: HashMap::new().into(),
+            }),
+        );
+        type_mapping.insert(
+            "float".into(),
+            unifier.add_ty(TypeEnum::TObj {
+                obj_id: DefinitionId(1),
+                fields: HashMap::new().into(),
+                params: HashMap::new().into(),
+            }),
+        );
+        type_mapping.insert(
+            "bool".into(),
+            unifier.add_ty(TypeEnum::TObj {
+                obj_id: DefinitionId(2),
+                fields: HashMap::new().into(),
+                params: HashMap::new().into(),
+            }),
+        );
+        let (v0, id) = unifier.get_fresh_var();
+        type_mapping.insert(
+            "Foo".into(),
+            unifier.add_ty(TypeEnum::TObj {
+                obj_id: DefinitionId(3),
+                fields: [("a".into(), v0)].iter().cloned().collect::<HashMap<_, _>>().into(),
+                params: [(id, v0)].iter().cloned().collect::<HashMap<_, _>>().into(),
+            }),
+        );
+
+        TestEnvironment { unifier, type_mapping }
+    }
+
+    fn parse(&mut self, typ: &str, mapping: &Mapping<String>) -> Type {
+        let result = self.internal_parse(typ, mapping);
+        assert!(result.1.is_empty());
+        result.0
+    }
+
+    fn internal_parse<'a, 'b>(
+        &'a mut self,
+        typ: &'b str,
+        mapping: &Mapping<String>,
+    ) -> (Type, &'b str) {
+        // for testing only, so we can just panic when the input is malformed
+        let end = typ.find(|c| ['[', ',', ']', '='].contains(&c)).unwrap_or_else(|| typ.len());
+        match &typ[..end] {
+            "Tuple" => {
+                let mut s = &typ[end..];
+                assert!(&s[0..1] == "[");
+                let mut ty = Vec::new();
+                while &s[0..1] != "]" {
+                    let result = self.internal_parse(&s[1..], mapping);
+                    ty.push(result.0);
+                    s = result.1;
+                }
+                (self.unifier.add_ty(TypeEnum::TTuple { ty }), &s[1..])
+            }
+            "List" => {
+                assert!(&typ[end..end + 1] == "[");
+                let (ty, s) = self.internal_parse(&typ[end + 1..], mapping);
+                assert!(&s[0..1] == "]");
+                (self.unifier.add_ty(TypeEnum::TList { ty }), &s[1..])
+            }
+            "Record" => {
+                let mut s = &typ[end..];
+                assert!(&s[0..1] == "[");
+                let mut fields = HashMap::new();
+                while &s[0..1] != "]" {
+                    let eq = s.find('=').unwrap();
+                    let key = s[1..eq].to_string();
+                    let result = self.internal_parse(&s[eq + 1..], mapping);
+                    fields.insert(key, result.0);
+                    s = result.1;
+                }
+                (self.unifier.add_record(fields), &s[1..])
+            }
+            x => {
+                let mut s = &typ[end..];
+                let ty = mapping.get(x).cloned().unwrap_or_else(|| {
+                    // mapping should be type variables, type_mapping should be concrete types
+                    // we should not resolve the type of type variables.
+                    let mut ty = *self.type_mapping.get(x).unwrap();
+                    let te = self.unifier.get_ty(ty);
+                    if let TypeEnum::TObj { params, .. } = &*te.as_ref() {
+                        let params = params.borrow();
+                        if !params.is_empty() {
+                            assert!(&s[0..1] == "[");
+                            let mut p = Vec::new();
+                            while &s[0..1] != "]" {
+                                let result = self.internal_parse(&s[1..], mapping);
+                                p.push(result.0);
+                                s = result.1;
+                            }
+                            s = &s[1..];
+                            ty = self
+                                .unifier
+                                .subst(ty, &params.keys().cloned().zip(p.into_iter()).collect())
+                                .unwrap_or(ty);
+                        }
+                    }
+                    ty
+                });
+                (ty, s)
+            }
+        }
+    }
+}
+
+#[test_case(2,
+    &[("v1", "v2"), ("v2", "float")],
+    &[("v1", "float"), ("v2", "float")]
+    ; "simple variable"
+)]
+#[test_case(2,
+    &[("v1", "List[v2]"), ("v1", "List[float]")],
+    &[("v1", "List[float]"), ("v2", "float")]
+    ; "list element"
+)]
+#[test_case(3,
+    &[
+        ("v1", "Record[a=v3,b=v3]"),
+        ("v2", "Record[b=float,c=v3]"),
+        ("v1", "v2")
+    ],
+    &[
+        ("v1", "Record[a=float,b=float,c=float]"),
+        ("v2", "Record[a=float,b=float,c=float]"),
+        ("v3", "float")
+    ]
+    ; "record merge"
+)]
+#[test_case(3,
+    &[
+        ("v1", "Record[a=float]"),
+        ("v2", "Foo[v3]"),
+        ("v1", "v2")
+    ],
+    &[
+        ("v1", "Foo[float]"),
+        ("v3", "float")
+    ]
+    ; "record obj merge"
+)]
+/// Test cases for valid unifications.
+fn test_unify(
+    variable_count: u32,
+    unify_pairs: &[(&'static str, &'static str)],
+    verify_pairs: &[(&'static str, &'static str)],
+) {
+    let unify_count = unify_pairs.len();
+    // test all permutations...
+    for perm in unify_pairs.iter().permutations(unify_count) {
+        let mut env = TestEnvironment::new();
+        let mut mapping = HashMap::new();
+        for i in 1..=variable_count {
+            let v = env.unifier.get_fresh_var();
+            mapping.insert(format!("v{}", i), v.0);
+        }
+        // unification may have side effect when we do type resolution, so freeze the types
+        // before doing unification.
+        let mut pairs = Vec::new();
+        for (a, b) in perm.iter() {
+            let t1 = env.parse(a, &mapping);
+            let t2 = env.parse(b, &mapping);
+            pairs.push((t1, t2));
+        }
+        for (t1, t2) in pairs {
+            env.unifier.unify(t1, t2).unwrap();
+        }
+        for (a, b) in verify_pairs.iter() {
+            println!("{} = {}", a, b);
+            let t1 = env.parse(a, &mapping);
+            let t2 = env.parse(b, &mapping);
+            assert!(env.unifier.eq(t1, t2));
+        }
+    }
+}
+
+#[test_case(2,
+    &[
+        ("v1", "Tuple[int]"),
+        ("v2", "List[int]"),
+    ],
+    (("v1", "v2"), "Cannot unify TList with TTuple")
+    ; "type mismatch"
+)]
+#[test_case(2,
+    &[
+        ("v1", "Tuple[int]"),
+        ("v2", "Tuple[float]"),
+    ],
+    (("v1", "v2"), "Cannot unify objects with ID 0 and 1")
+    ; "tuple parameter mismatch"
+)]
+#[test_case(2,
+    &[
+        ("v1", "Tuple[int,int]"),
+        ("v2", "Tuple[int]"),
+    ],
+    (("v1", "v2"), "Cannot unify tuples with length 2 and 1")
+    ; "tuple length mismatch"
+)]
+#[test_case(3,
+    &[
+        ("v1", "Record[a=float,b=int]"),
+        ("v2", "Foo[v3]"),
+    ],
+    (("v1", "v2"), "No such attribute b")
+    ; "record obj merge"
+)]
+#[test_case(2,
+    &[
+        ("v1", "List[v2]"),
+    ],
+    (("v1", "v2"), "Recursive type is prohibited.")
+    ; "recursive type for lists"
+)]
+/// Test cases for invalid unifications.
+fn test_invalid_unification(
+    variable_count: u32,
+    unify_pairs: &[(&'static str, &'static str)],
+    errornous_pair: ((&'static str, &'static str), &'static str),
+) {
+    let mut env = TestEnvironment::new();
+    let mut mapping = HashMap::new();
+    for i in 1..=variable_count {
+        let v = env.unifier.get_fresh_var();
+        mapping.insert(format!("v{}", i), v.0);
+    }
+    // unification may have side effect when we do type resolution, so freeze the types
+    // before doing unification.
+    let mut pairs = Vec::new();
+    for (a, b) in unify_pairs.iter() {
+        let t1 = env.parse(a, &mapping);
+        let t2 = env.parse(b, &mapping);
+        pairs.push((t1, t2));
+    }
+    let (t1, t2) =
+        (env.parse(errornous_pair.0 .0, &mapping), env.parse(errornous_pair.0 .1, &mapping));
+    for (a, b) in pairs {
+        env.unifier.unify(a, b).unwrap();
+    }
+    assert_eq!(env.unifier.unify(t1, t2), Err(errornous_pair.1.to_string()));
+}
+
+#[test]
+fn test_virtual() {
+    let mut env = TestEnvironment::new();
+    let int = env.parse("int", &HashMap::new());
+    let fun = env.unifier.add_ty(TypeEnum::TFunc(
+        FunSignature { args: vec![], ret: int, vars: HashMap::new() }.into(),
+    ));
+    let bar = env.unifier.add_ty(TypeEnum::TObj {
+        obj_id: DefinitionId(5),
+        fields: [("f".to_string(), fun), ("a".to_string(), int)]
+            .iter()
+            .cloned()
+            .collect::<HashMap<_, _>>()
+            .into(),
+        params: HashMap::new().into(),
+    });
+    let v0 = env.unifier.get_fresh_var().0;
+    let v1 = env.unifier.get_fresh_var().0;
+
+    let a = env.unifier.add_ty(TypeEnum::TVirtual { ty: bar });
+    let b = env.unifier.add_ty(TypeEnum::TVirtual { ty: v0 });
+    let c = env.unifier.add_record([("f".to_string(), v1)].iter().cloned().collect());
+    env.unifier.unify(a, b).unwrap();
+    env.unifier.unify(b, c).unwrap();
+    assert!(env.unifier.eq(v1, fun));
+
+    let d = env.unifier.add_record([("a".to_string(), v1)].iter().cloned().collect());
+    assert_eq!(env.unifier.unify(b, d), Err("Cannot access field a for virtual type".to_string()));
+
+    let d = env.unifier.add_record([("b".to_string(), v1)].iter().cloned().collect());
+    assert_eq!(env.unifier.unify(b, d), Err("No such attribute b".to_string()));
+}
+
+#[test]
+fn test_typevar_range() {
+    let mut env = TestEnvironment::new();
+    let int = env.parse("int", &HashMap::new());
+    let boolean = env.parse("bool", &HashMap::new());
+    let float = env.parse("float", &HashMap::new());
+    let int_list = env.parse("List[int]", &HashMap::new());
+    let float_list = env.parse("List[float]", &HashMap::new());
+
+    // unification between v and int
+    // where v in (int, bool)
+    let v = env.unifier.get_fresh_var_with_range(&[int, boolean]).0;
+    env.unifier.unify(int, v).unwrap();
+
+    // unification between v and List[int]
+    // where v in (int, bool)
+    let v = env.unifier.get_fresh_var_with_range(&[int, boolean]).0;
+    assert_eq!(
+        env.unifier.unify(int_list, v),
+        Err("Cannot unify type variable 3 with TList due to incompatible value range".to_string())
+    );
+
+    // unification between v and float
+    // where v in (int, bool)
+    let v = env.unifier.get_fresh_var_with_range(&[int, boolean]).0;
+    assert_eq!(
+        env.unifier.unify(float, v),
+        Err("Cannot unify type variable 4 with TObj due to incompatible value range".to_string())
+    );
+
+    let v1 = env.unifier.get_fresh_var_with_range(&[int, boolean]).0;
+    let v1_list = env.unifier.add_ty(TypeEnum::TList { ty: v1 });
+    let v = env.unifier.get_fresh_var_with_range(&[int, v1_list]).0;
+    // unification between v and int
+    // where v in (int, List[v1]), v1 in (int, bool)
+    env.unifier.unify(int, v).unwrap();
+
+    let v = env.unifier.get_fresh_var_with_range(&[int, v1_list]).0;
+    // unification between v and List[int]
+    // where v in (int, List[v1]), v1 in (int, bool)
+    env.unifier.unify(int_list, v).unwrap();
+
+    let v = env.unifier.get_fresh_var_with_range(&[int, v1_list]).0;
+    // unification between v and List[float]
+    // where v in (int, List[v1]), v1 in (int, bool)
+    assert_eq!(
+        env.unifier.unify(float_list, v),
+        Err("Cannot unify type variable 8 with TList due to incompatible value range".to_string())
+    );
+
+    let a = env.unifier.get_fresh_var_with_range(&[int, float]).0;
+    let b = env.unifier.get_fresh_var_with_range(&[boolean, float]).0;
+    env.unifier.unify(a, b).unwrap();
+    env.unifier.unify(a, float).unwrap();
+
+    let a = env.unifier.get_fresh_var_with_range(&[int, float]).0;
+    let b = env.unifier.get_fresh_var_with_range(&[boolean, float]).0;
+    env.unifier.unify(a, b).unwrap();
+    assert_eq!(
+        env.unifier.unify(a, int),
+        Err("Cannot unify type variable 12 with TObj due to incompatible value range".into())
+    );
+
+    let a = env.unifier.get_fresh_var_with_range(&[int, float]).0;
+    let b = env.unifier.get_fresh_var_with_range(&[boolean, float]).0;
+    let a_list = env.unifier.add_ty(TypeEnum::TList { ty: a });
+    let a_list = env.unifier.get_fresh_var_with_range(&[a_list]).0;
+    let b_list = env.unifier.add_ty(TypeEnum::TList { ty: b });
+    let b_list = env.unifier.get_fresh_var_with_range(&[b_list]).0;
+    env.unifier.unify(a_list, b_list).unwrap();
+    let float_list = env.unifier.add_ty(TypeEnum::TList { ty: float });
+    env.unifier.unify(a_list, float_list).unwrap();
+    // previous unifications should not affect a and b
+    env.unifier.unify(a, int).unwrap();
+
+    let a = env.unifier.get_fresh_var_with_range(&[int, float]).0;
+    let b = env.unifier.get_fresh_var_with_range(&[boolean, float]).0;
+    let a_list = env.unifier.add_ty(TypeEnum::TList { ty: a });
+    let b_list = env.unifier.add_ty(TypeEnum::TList { ty: b });
+    env.unifier.unify(a_list, b_list).unwrap();
+    let int_list = env.unifier.add_ty(TypeEnum::TList { ty: int });
+    assert_eq!(
+        env.unifier.unify(a_list, int_list),
+        Err("Cannot unify type variable 19 with TObj due to incompatible value range".into())
+    );
+
+    let a = env.unifier.get_fresh_var_with_range(&[int, float]).0;
+    let b = env.unifier.get_fresh_var().0;
+    let a_list = env.unifier.add_ty(TypeEnum::TList { ty: a });
+    let a_list = env.unifier.get_fresh_var_with_range(&[a_list]).0;
+    let b_list = env.unifier.add_ty(TypeEnum::TList { ty: b });
+    env.unifier.unify(a_list, b_list).unwrap();
+    assert_eq!(
+        env.unifier.unify(b, boolean),
+        Err("Cannot unify type variable 21 with TObj due to incompatible value range".into())
+    );
+}
+
+#[test]
+fn test_rigid_var() {
+    let mut env = TestEnvironment::new();
+    let a = env.unifier.get_fresh_rigid_var().0;
+    let b = env.unifier.get_fresh_rigid_var().0;
+    let x = env.unifier.get_fresh_var().0;
+    let list_a = env.unifier.add_ty(TypeEnum::TList { ty: a });
+    let list_x = env.unifier.add_ty(TypeEnum::TList { ty: x });
+    let int = env.parse("int", &HashMap::new());
+    let list_int = env.parse("List[int]", &HashMap::new());
+
+    assert_eq!(env.unifier.unify(a, b), Err("Cannot unify TRigidVar with TRigidVar".to_string()));
+    env.unifier.unify(list_a, list_x).unwrap();
+    assert_eq!(
+        env.unifier.unify(list_x, list_int),
+        Err("Cannot unify TObj with TRigidVar".to_string())
+    );
+
+    env.unifier.replace_rigid_var(a, int);
+    env.unifier.unify(list_x, list_int).unwrap();
+}
+
+#[test]
+fn test_instantiation() {
+    let mut env = TestEnvironment::new();
+    let int = env.parse("int", &HashMap::new());
+    let boolean = env.parse("bool", &HashMap::new());
+    let float = env.parse("float", &HashMap::new());
+    let list_int = env.parse("List[int]", &HashMap::new());
+
+    let obj_map: HashMap<_, _> =
+        [(0usize, "int"), (1, "float"), (2, "bool")].iter().cloned().collect();
+
+    let v = env.unifier.get_fresh_var_with_range(&[int, boolean]).0;
+    let list_v = env.unifier.add_ty(TypeEnum::TList { ty: v });
+    let v1 = env.unifier.get_fresh_var_with_range(&[list_v, int]).0;
+    let v2 = env.unifier.get_fresh_var_with_range(&[list_int, float]).0;
+    let t = env.unifier.get_fresh_rigid_var().0;
+    let tuple = env.unifier.add_ty(TypeEnum::TTuple { ty: vec![v, v1, v2] });
+    let v3 = env.unifier.get_fresh_var_with_range(&[tuple, t]).0;
+    // t = TypeVar('t')
+    // v = TypeVar('v', int, bool)
+    // v1 = TypeVar('v1', 'list[v]', int)
+    // v2 = TypeVar('v2', 'list[int]', float)
+    // v3 = TypeVar('v3', tuple[v, v1, v2], t)
+    // what values can v3 take?
+
+    let types = env.unifier.get_instantiations(v3).unwrap();
+    let expected_types = indoc! {"
+        tuple[bool, int, float]
+        tuple[bool, int, list[int]]
+        tuple[bool, list[bool], float]
+        tuple[bool, list[bool], list[int]]
+        tuple[bool, list[int], float]
+        tuple[bool, list[int], list[int]]
+        tuple[int, int, float]
+        tuple[int, int, list[int]]
+        tuple[int, list[bool], float]
+        tuple[int, list[bool], list[int]]
+        tuple[int, list[int], float]
+        tuple[int, list[int], list[int]]
+        v5"
+    }
+    .split('\n')
+    .collect_vec();
+    let types = types
+        .iter()
+        .map(|ty| {
+            env.unifier.stringify(*ty, &mut |i| obj_map.get(&i).unwrap().to_string(), &mut |i| {
+                format!("v{}", i)
+            })
+        })
+        .sorted()
+        .collect_vec();
+    assert_eq!(expected_types, types);
+}

nac3core/src/typecheck/unification_table.rs

@@ -0,0 +1,87 @@
+use std::rc::Rc;
+
+#[derive(Copy, Clone, PartialEq, Eq, Debug, Hash)]
+pub struct UnificationKey(usize);
+
+pub struct UnificationTable<V> {
+    parents: Vec<usize>,
+    ranks: Vec<u32>,
+    values: Vec<V>,
+}
+
+impl<V> UnificationTable<V> {
+    pub fn new() -> UnificationTable<V> {
+        UnificationTable { parents: Vec::new(), ranks: Vec::new(), values: Vec::new() }
+    }
+
+    pub fn new_key(&mut self, v: V) -> UnificationKey {
+        let index = self.parents.len();
+        self.parents.push(index);
+        self.ranks.push(0);
+        self.values.push(v);
+        UnificationKey(index)
+    }
+
+    pub fn unify(&mut self, a: UnificationKey, b: UnificationKey) {
+        let mut a = self.find(a);
+        let mut b = self.find(b);
+        if a == b {
+            return;
+        }
+        if self.ranks[a] < self.ranks[b] {
+            std::mem::swap(&mut a, &mut b);
+        }
+        self.parents[b] = a;
+        if self.ranks[a] == self.ranks[b] {
+            self.ranks[a] += 1;
+        }
+    }
+
+    pub fn probe_value(&mut self, a: UnificationKey) -> &V {
+        let index = self.find(a);
+        &self.values[index]
+    }
+
+    pub fn set_value(&mut self, a: UnificationKey, v: V) {
+        let index = self.find(a);
+        self.values[index] = v;
+    }
+
+    pub fn unioned(&mut self, a: UnificationKey, b: UnificationKey) -> bool {
+        self.find(a) == self.find(b)
+    }
+
+    pub fn get_representative(&mut self, key: UnificationKey) -> UnificationKey {
+        UnificationKey(self.find(key))
+    }
+
+    fn find(&mut self, key: UnificationKey) -> usize {
+        let mut root = key.0;
+        let mut parent = self.parents[root];
+        while root != parent {
+            // a = parent.parent
+            let a = self.parents[parent];
+            // root.parent = parent.parent
+            self.parents[root] = a;
+            root = parent;
+            // parent = root.parent
+            parent = a;
+        }
+        parent
+    }
+}
+
+impl<V> UnificationTable<Rc<V>>
+where
+    V: Clone,
+{
+    pub fn get_send(&self) -> UnificationTable<V> {
+        let values = self.values.iter().map(|v| v.as_ref().clone()).collect();
+        UnificationTable { parents: self.parents.clone(), ranks: self.ranks.clone(), values }
+    }
+
+    pub fn from_send(table: &UnificationTable<V>) -> UnificationTable<Rc<V>> {
+        let values = table.values.iter().cloned().map(Rc::new).collect();
+        UnificationTable { parents: table.parents.clone(), ranks: table.ranks.clone(), values }
+    }
+}

nac3core/src/typedef.rs

@@ -1,60 +0,0 @@
-use std::collections::HashMap;
-use std::rc::Rc;
-
-#[derive(PartialEq, Eq, Copy, Clone, Hash, Debug)]
-pub struct PrimitiveId(pub(crate) usize);
-
-#[derive(PartialEq, Eq, Copy, Clone, Hash, Debug)]
-pub struct ClassId(pub(crate) usize);
-
-#[derive(PartialEq, Eq, Copy, Clone, Hash, Debug)]
-pub struct ParamId(pub(crate) usize);
-
-#[derive(PartialEq, Eq, Copy, Clone, Hash, Debug)]
-pub struct VariableId(pub(crate) usize);
-
-#[derive(PartialEq, Eq, Clone, Hash, Debug)]
-pub enum TypeEnum {
-    BotType,
-    SelfType,
-    PrimitiveType(PrimitiveId),
-    ClassType(ClassId),
-    VirtualClassType(ClassId),
-    ParametricType(ParamId, Vec<Rc<TypeEnum>>),
-    TypeVariable(VariableId),
-}
-
-pub type Type = Rc<TypeEnum>;
-
-#[derive(Clone)]
-pub struct FnDef {
-    // we assume methods first argument to be SelfType,
-    // so the first argument is not contained here
-    pub args: Vec<Type>,
-    pub result: Option<Type>,
-}
-
-#[derive(Clone)]
-pub struct TypeDef<'a> {
-    pub name: &'a str,
-    pub fields: HashMap<&'a str, Type>,
-    pub methods: HashMap<&'a str, FnDef>,
-}
-
-#[derive(Clone)]
-pub struct ClassDef<'a> {
-    pub base: TypeDef<'a>,
-    pub parents: Vec<ClassId>,
-}
-
-#[derive(Clone)]
-pub struct ParametricDef<'a> {
-    pub base: TypeDef<'a>,
-    pub params: Vec<VariableId>,
-}
-
-#[derive(Clone)]
-pub struct VarDef<'a> {
-    pub name: &'a str,
-    pub bound: Vec<Type>,
-}

shell.nix

@@ -4,6 +4,6 @@ in
   pkgs.stdenv.mkDerivation {
     name = "nac3-env";
     buildInputs = with pkgs; [
-      llvm_10 clang_10 cargo rustc libffi libxml2 clippy
+      llvm_11 clang_11 cargo rustc libffi libxml2 clippy
     ];
   }