core: improve binop and cmpop error messages

nac3core/src/codegen/expr.rs

@@ -21,7 +21,7 @@ use crate::{
         DefinitionId, TopLevelDef,
     },
     typecheck::{
-        magic_methods::{binop_assign_name, binop_name, unaryop_name},
+        magic_methods::{BinOpVariant, OpInfo},
         typedef::{FunSignature, FuncArg, Type, TypeEnum, TypeVarId, Unifier, VarMap},
     },
 };
@@ -1167,7 +1167,7 @@ pub fn gen_binop_expr_with_values<'ctx, G: CodeGenerator>(
     op: Operator,
     right: (&Option<Type>, BasicValueEnum<'ctx>),
     loc: Location,
-    is_aug_assign: bool,
+    variant: BinOpVariant,
 ) -> Result<Option<ValueEnum<'ctx>>, String> {
     let (left_ty, left_val) = left;
     let (right_ty, right_val) = right;
@@ -1222,7 +1222,10 @@ pub fn gen_binop_expr_with_values<'ctx, G: CodeGenerator>(
                     generator,
                     ctx,
                     ndarray_dtype1,
-                    if is_aug_assign { Some(left_val) } else { None },
+                    match variant {
+                        BinOpVariant::Normal => None,
+                        BinOpVariant::AugAssign => Some(left_val),
+                    },
                     left_val,
                     right_val,
                 )?
@@ -1231,7 +1234,10 @@ pub fn gen_binop_expr_with_values<'ctx, G: CodeGenerator>(
                     generator,
                     ctx,
                     ndarray_dtype1,
-                    if is_aug_assign { Some(left_val) } else { None },
+                    match variant {
+                        BinOpVariant::Normal => None,
+                        BinOpVariant::AugAssign => Some(left_val),
+                    },
                     (left_val.as_base_value().into(), false),
                     (right_val.as_base_value().into(), false),
                     |generator, ctx, (lhs, rhs)| {
@@ -1242,7 +1248,7 @@ pub fn gen_binop_expr_with_values<'ctx, G: CodeGenerator>(
                             op,
                             (&Some(ndarray_dtype2), rhs),
                             ctx.current_loc,
-                            is_aug_assign,
+                            variant,
                         )?
                         .unwrap()
                         .to_basic_value_enum(
@@ -1267,7 +1273,10 @@ pub fn gen_binop_expr_with_values<'ctx, G: CodeGenerator>(
                 generator,
                 ctx,
                 ndarray_dtype,
-                if is_aug_assign { Some(ndarray_val) } else { None },
+                match variant {
+                    BinOpVariant::Normal => None,
+                    BinOpVariant::AugAssign => Some(ndarray_val),
+                },
                 (left_val, !is_ndarray1),
                 (right_val, !is_ndarray2),
                 |generator, ctx, (lhs, rhs)| {
@@ -1278,7 +1287,7 @@ pub fn gen_binop_expr_with_values<'ctx, G: CodeGenerator>(
                         op,
                         (&Some(ndarray_dtype), rhs),
                         ctx.current_loc,
-                        is_aug_assign,
+                        variant,
                     )?
                     .unwrap()
                     .to_basic_value_enum(ctx, generator, ndarray_dtype)
@@ -1293,13 +1302,15 @@ pub fn gen_binop_expr_with_values<'ctx, G: CodeGenerator>(
             unreachable!("must be tobj")
         };
         let (op_name, id) = {
-            let (binop_name, binop_assign_name) =
-                (binop_name(op).into(), binop_assign_name(op).into());
+            let normal_method_name = OpInfo::from_binop(op, BinOpVariant::Normal).method_name;
+            let assign_method_name = OpInfo::from_binop(op, BinOpVariant::AugAssign).method_name;
+
             // if is aug_assign, try aug_assign operator first
-            if is_aug_assign && fields.contains_key(&binop_assign_name) {
-                (binop_assign_name, *obj_id)
+            if variant == BinOpVariant::AugAssign && fields.contains_key(&assign_method_name.into())
+            {
+                (assign_method_name.into(), *obj_id)
             } else {
-                (binop_name, *obj_id)
+                (normal_method_name.into(), *obj_id)
             }
         };
 
@@ -1349,7 +1360,7 @@ pub fn gen_binop_expr<'ctx, G: CodeGenerator>(
     op: Operator,
     right: &Expr<Option<Type>>,
     loc: Location,
-    is_aug_assign: bool,
+    variant: BinOpVariant,
 ) -> Result<Option<ValueEnum<'ctx>>, String> {
     let left_val = if let Some(v) = generator.gen_expr(ctx, left)? {
         v.to_basic_value_enum(ctx, generator, left.custom.unwrap())?
@@ -1369,7 +1380,7 @@ pub fn gen_binop_expr<'ctx, G: CodeGenerator>(
         op,
         (&right.custom, right_val),
         loc,
-        is_aug_assign,
+        variant,
     )
 }
 
@@ -1453,7 +1464,10 @@ pub fn gen_unaryop_expr_with_values<'ctx, G: CodeGenerator>(
             if op == ast::Unaryop::Invert {
                 ast::Unaryop::Not
             } else {
-                unreachable!("ufunc {} not supported for ndarray[bool, N]", unaryop_name(op))
+                unreachable!(
+                    "ufunc {} not supported for ndarray[bool, N]",
+                    OpInfo::from_unaryop(op).method_name
+                )
             }
         } else {
             op
@@ -2343,7 +2357,15 @@ pub fn gen_expr<'ctx, G: CodeGenerator>(
             }
         }
         ExprKind::BinOp { op, left, right } => {
-            return gen_binop_expr(generator, ctx, left, *op, right, expr.location, false);
+            return gen_binop_expr(
+                generator,
+                ctx,
+                left,
+                *op,
+                right,
+                expr.location,
+                BinOpVariant::Normal,
+            );
         }
         ExprKind::UnaryOp { op, operand } => return gen_unaryop_expr(generator, ctx, *op, operand),
         ExprKind::Compare { left, ops, comparators } => {

nac3core/src/codegen/numpy.rs

@@ -11,8 +11,7 @@ use crate::{
             call_ndarray_calc_broadcast_index, call_ndarray_calc_nd_indices,
             call_ndarray_calc_size,
         },
-        llvm_intrinsics,
-        llvm_intrinsics::call_memcpy_generic,
+        llvm_intrinsics::{self, call_memcpy_generic},
         stmt::{gen_for_callback_incrementing, gen_for_range_callback, gen_if_else_expr_callback},
         CodeGenContext, CodeGenerator,
     },
@@ -22,7 +21,10 @@ use crate::{
         numpy::{make_ndarray_ty, unpack_ndarray_var_tys},
         DefinitionId,
     },
-    typecheck::typedef::{FunSignature, Type, TypeEnum},
+    typecheck::{
+        magic_methods::BinOpVariant,
+        typedef::{FunSignature, Type, TypeEnum},
+    },
 };
 use inkwell::types::{AnyTypeEnum, BasicTypeEnum, PointerType};
 use inkwell::{
@@ -1632,7 +1634,7 @@ pub fn ndarray_matmul_2d<'ctx, G: CodeGenerator>(
                     Operator::Mult,
                     (&Some(elem_ty), b),
                     ctx.current_loc,
-                    false,
+                    BinOpVariant::Normal,
                 )?
                 .unwrap()
                 .to_basic_value_enum(ctx, generator, elem_ty)?;
@@ -1645,7 +1647,7 @@ pub fn ndarray_matmul_2d<'ctx, G: CodeGenerator>(
                     Operator::Add,
                     (&Some(elem_ty), a_mul_b),
                     ctx.current_loc,
-                    false,
+                    BinOpVariant::Normal,
                 )?
                 .unwrap()
                 .to_basic_value_enum(ctx, generator, elem_ty)?;

nac3core/src/codegen/stmt.rs

@@ -11,7 +11,10 @@ use crate::{
         gen_in_range_check,
     },
     toplevel::{helper::PrimDef, numpy::unpack_ndarray_var_tys, DefinitionId, TopLevelDef},
-    typecheck::typedef::{FunSignature, Type, TypeEnum},
+    typecheck::{
+        magic_methods::BinOpVariant,
+        typedef::{FunSignature, Type, TypeEnum},
+    },
 };
 use inkwell::{
     attributes::{Attribute, AttributeLoc},
@@ -1574,7 +1577,15 @@ pub fn gen_stmt<G: CodeGenerator>(
         StmtKind::For { .. } => generator.gen_for(ctx, stmt)?,
         StmtKind::With { .. } => generator.gen_with(ctx, stmt)?,
         StmtKind::AugAssign { target, op, value, .. } => {
-            let value = gen_binop_expr(generator, ctx, target, *op, value, stmt.location, true)?;
+            let value = gen_binop_expr(
+                generator,
+                ctx,
+                target,
+                *op,
+                value,
+                stmt.location,
+                BinOpVariant::AugAssign,
+            )?;
             generator.gen_assign(ctx, target, value.unwrap())?;
         }
         StmtKind::Try { .. } => gen_try(generator, ctx, stmt)?,

nac3core/src/typecheck/magic_methods.rs

@@ -5,7 +5,7 @@ use crate::typecheck::{
     type_inferencer::*,
     typedef::{FunSignature, FuncArg, Type, TypeEnum, Unifier, VarMap},
 };
-use itertools::Itertools;
+use itertools::{iproduct, Itertools};
 use nac3parser::ast::StrRef;
 use nac3parser::ast::{Cmpop, Operator, Unaryop};
 use std::cmp::max;
@@ -13,64 +13,93 @@ use std::collections::HashMap;
 use std::rc::Rc;
 use strum::IntoEnumIterator;
 
-#[must_use]
-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__",
-    }
+/// Details about an operator (unary, binary, etc...) in Python
+#[derive(Debug, Clone, Copy)]
+pub struct OpInfo {
+    /// The method name of the binary operator.
+    /// For addition, this would be `__add__`, and `__iadd__` if
+    /// it is the augmented assigning variant.
+    pub method_name: &'static str,
+    /// The symbol of the binary operator.
+    /// For addition, this would be `+`, and `+=` if
+    /// it is the augmented assigning variant.
+    pub symbol: &'static str,
 }
 
-#[must_use]
-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__",
-    }
+/// Helper macro to conveniently build an [`OpInfo`].
+///
+/// Example usage: `make_info("add", "+")` generates `OpInfo { name: "__add__", symbol: "+" }`
+macro_rules! make_info {
+    ($name:expr, $symbol:expr) => {
+        OpInfo { method_name: concat!("__", $name, "__"), symbol: $symbol }
+    };
 }
 
-#[must_use]
-pub fn unaryop_name(op: Unaryop) -> &'static str {
-    match op {
-        Unaryop::UAdd => "__pos__",
-        Unaryop::USub => "__neg__",
-        Unaryop::Not => "__not__",
-        Unaryop::Invert => "__inv__",
-    }
+/// The variant of a binary operator.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum BinOpVariant {
+    /// The normal variant.
+    /// For addition, it would be `+`.
+    Normal,
+    /// The "Augmented Assigning Operator" variant.
+    /// For addition, it would be `+=`.
+    AugAssign,
 }
 
-#[must_use]
-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,
+impl OpInfo {
+    #[must_use]
+    pub fn from_binop(op: Operator, variant: BinOpVariant) -> Self {
+        // Helper macro to generate both the normal variant [`OpInfo`] and the
+        // augmented assigning variant [`OpInfo`] for a binary operator conveniently.
+        macro_rules! info {
+            ($name:literal, $symbol:literal) => {
+                (make_info!($name, $symbol), make_info!(concat!("i", $name), concat!($symbol, "=")))
+            };
+        }
+
+        let (normal_variant, aug_assign_variant) = match op {
+            Operator::Add => info!("add", "+"),
+            Operator::Sub => info!("sub", "-"),
+            Operator::Div => info!("truediv", "/"),
+            Operator::Mod => info!("mod", "%"),
+            Operator::Mult => info!("mul", "*"),
+            Operator::Pow => info!("pow", "**"),
+            Operator::BitOr => info!("or", "|"),
+            Operator::BitXor => info!("xor", "^"),
+            Operator::BitAnd => info!("and", "&"),
+            Operator::LShift => info!("lshift", "<<"),
+            Operator::RShift => info!("rshift", ">>"),
+            Operator::FloorDiv => info!("floordiv", "//"),
+            Operator::MatMult => info!("matmul", "@"),
+        };
+
+        match variant {
+            BinOpVariant::Normal => normal_variant,
+            BinOpVariant::AugAssign => aug_assign_variant,
+        }
+    }
+
+    #[must_use]
+    pub fn from_unaryop(op: Unaryop) -> Self {
+        match op {
+            Unaryop::UAdd => make_info!("pos", "+"),
+            Unaryop::USub => make_info!("neg", "-"),
+            Unaryop::Not => make_info!("not", "not"), // i.e., `not False`, so the symbol is just `not`.
+            Unaryop::Invert => make_info!("inv", "~"),
+        }
+    }
+
+    #[must_use]
+    pub fn from_cmpop(op: Cmpop) -> Option<Self> {
+        match op {
+            Cmpop::Lt => Some(make_info!("lt", "<")),
+            Cmpop::LtE => Some(make_info!("le", "<=")),
+            Cmpop::Gt => Some(make_info!("gt", ">")),
+            Cmpop::GtE => Some(make_info!("ge", ">=")),
+            Cmpop::Eq => Some(make_info!("eq", "==")),
+            Cmpop::NotEq => Some(make_info!("ne", "!=")),
+            _ => None,
+        }
     }
 }
 
@@ -115,23 +144,8 @@ pub fn impl_binop(
 
         let ret_ty = ret_ty.unwrap_or_else(|| unifier.get_fresh_var(None, None).ty);
 
-        for op in ops {
-            fields.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(),
-                        }],
-                    })),
-                    false,
-                )
-            });
-
-            fields.insert(binop_assign_name(*op).into(), {
+        for (op, variant) in iproduct!(ops, [BinOpVariant::Normal, BinOpVariant::AugAssign]) {
+            fields.insert(OpInfo::from_binop(*op, variant).method_name.into(), {
                 (
                     unifier.add_ty(TypeEnum::TFunc(FunSignature {
                         ret: ret_ty,
@@ -155,7 +169,7 @@ pub fn impl_unaryop(unifier: &mut Unifier, ty: Type, ret_ty: Option<Type>, ops:
 
         for op in ops {
             fields.insert(
-                unaryop_name(*op).into(),
+                OpInfo::from_unaryop(*op).method_name.into(),
                 (
                     unifier.add_ty(TypeEnum::TFunc(FunSignature {
                         ret: ret_ty,
@@ -195,7 +209,7 @@ pub fn impl_cmpop(
 
         for op in ops {
             fields.insert(
-                comparison_name(*op).unwrap().into(),
+                OpInfo::from_cmpop(*op).unwrap().method_name.into(),
                 (
                     unifier.add_ty(TypeEnum::TFunc(FunSignature {
                         ret: ret_ty,

nac3core/src/typecheck/type_error.rs

@@ -1,24 +1,47 @@
 use std::collections::HashMap;
 use std::fmt::Display;
 
-use crate::typecheck::typedef::TypeEnum;
+use crate::typecheck::{magic_methods::OpInfo, typedef::TypeEnum};
 
-use super::typedef::{RecordKey, Type, Unifier};
-use nac3parser::ast::{Location, StrRef};
+use super::{
+    magic_methods::BinOpVariant,
+    typedef::{RecordKey, Type, Unifier},
+};
+use itertools::Itertools;
+use nac3parser::ast::{Cmpop, Location, Operator, StrRef};
 
 #[derive(Debug, Clone)]
 pub enum TypeErrorKind {
-    TooManyArguments {
-        expected: usize,
-        got: usize,
+    GotMultipleValues {
+        name: StrRef,
+    },
+    TooManyArguments {
+        expected_min_count: usize,
+        expected_max_count: usize,
+        got_count: usize,
+    },
+    MissingArgs {
+        missing_arg_names: Vec<StrRef>,
     },
-    MissingArgs(String),
     UnknownArgName(StrRef),
     IncorrectArgType {
         name: StrRef,
         expected: Type,
         got: Type,
     },
+    UnsupportedBinaryOpTypes {
+        operator: Operator,
+        variant: BinOpVariant,
+        lhs_type: Type,
+        rhs_type: Type,
+        expected_rhs_type: Type,
+    },
+    UnsupportedComparsionOpTypes {
+        operator: Cmpop,
+        lhs_type: Type,
+        rhs_type: Type,
+        expected_rhs_type: Type,
+    },
     FieldUnificationError {
         field: RecordKey,
         types: (Type, Type),
@@ -78,19 +101,55 @@ impl<'a> Display for DisplayTypeError<'a> {
         use TypeErrorKind::*;
         let mut notes = Some(HashMap::new());
         match &self.err.kind {
-            TooManyArguments { expected, got } => {
-                write!(f, "Too many arguments. Expected {expected} but got {got}")
+            GotMultipleValues { name } => {
+                write!(f, "For multiple values for parameter {name}")
             }
-            MissingArgs(args) => {
+            TooManyArguments { expected_min_count, expected_max_count, got_count } => {
+                debug_assert!(expected_min_count <= expected_max_count);
+                if expected_min_count == expected_max_count {
+                    let expected_count = expected_min_count; // or expected_max_count
+                    write!(f, "Too many arguments. Expected {expected_count} but got {got_count}")
+                } else {
+                    write!(f, "Too many arguments. Expected {expected_min_count} to {expected_max_count} arguments but got {got_count}")
+                }
+            }
+            MissingArgs { missing_arg_names } => {
+                let args = missing_arg_names.iter().join(", ");
                 write!(f, "Missing arguments: {args}")
             }
+            UnsupportedBinaryOpTypes {
+                operator,
+                variant,
+                lhs_type,
+                rhs_type,
+                expected_rhs_type,
+            } => {
+                let op_symbol = OpInfo::from_binop(*operator, *variant).symbol;
+
+                let lhs_type_str = self.unifier.stringify_with_notes(*lhs_type, &mut notes);
+                let rhs_type_str = self.unifier.stringify_with_notes(*rhs_type, &mut notes);
+                let expected_rhs_type_str =
+                    self.unifier.stringify_with_notes(*expected_rhs_type, &mut notes);
+
+                write!(f, "Unsupported operand type(s) for {op_symbol}: '{lhs_type_str}' and '{rhs_type_str}' (right operand should have type {expected_rhs_type_str})")
+            }
+            UnsupportedComparsionOpTypes { operator, lhs_type, rhs_type, expected_rhs_type } => {
+                let op_symbol = OpInfo::from_cmpop(*operator).unwrap().symbol;
+
+                let lhs_type_str = self.unifier.stringify_with_notes(*lhs_type, &mut notes);
+                let rhs_type_str = self.unifier.stringify_with_notes(*rhs_type, &mut notes);
+                let expected_rhs_type_str =
+                    self.unifier.stringify_with_notes(*expected_rhs_type, &mut notes);
+
+                write!(f, "'{op_symbol}' not supported between instances of '{lhs_type_str}' and '{rhs_type_str}' (right operand should have type {expected_rhs_type_str})")
+            }
             UnknownArgName(name) => {
                 write!(f, "Unknown argument name: {name}")
             }
             IncorrectArgType { name, expected, got } => {
                 let expected = self.unifier.stringify_with_notes(*expected, &mut notes);
                 let got = self.unifier.stringify_with_notes(*got, &mut notes);
-                write!(f, "Incorrect argument type for {name}. Expected {expected}, but got {got}")
+                write!(f, "Incorrect argument type for parameter {name}. Expected {expected}, but got {got}")
             }
             FieldUnificationError { field, types, loc } => {
                 let lhs = self.unifier.stringify_with_notes(types.0, &mut notes);

nac3core/src/typecheck/type_inferencer/mod.rs

@@ -4,7 +4,9 @@ use std::iter::once;
 use std::ops::Not;
 use std::{cell::RefCell, sync::Arc};
 
-use super::typedef::{Call, FunSignature, FuncArg, RecordField, Type, TypeEnum, Unifier, VarMap};
+use super::typedef::{
+    Call, CallInfo, FunSignature, FuncArg, RecordField, Type, TypeEnum, Unifier, VarMap,
+};
 use super::{magic_methods::*, type_error::TypeError, typedef::CallId};
 use crate::toplevel::TopLevelDef;
 use crate::{
@@ -466,7 +468,8 @@ impl<'a> Fold<()> for Inferencer<'a> {
                 (None, None) => {}
             },
             ast::StmtKind::AugAssign { target, op, value, .. } => {
-                let res_ty = self.infer_bin_ops(stmt.location, target, *op, value, true)?;
+                let res_ty =
+                    self.infer_bin_ops(stmt.location, target, *op, value, BinOpVariant::AugAssign)?;
                 self.unify(res_ty, target.custom.unwrap(), &stmt.location)?;
             }
             ast::StmtKind::Assert { test, msg, .. } => {
@@ -548,7 +551,7 @@ impl<'a> Fold<()> for Inferencer<'a> {
             }
             ExprKind::BoolOp { values, .. } => Some(self.infer_bool_ops(values)?),
             ExprKind::BinOp { left, op, right } => {
-                Some(self.infer_bin_ops(expr.location, left, *op, right, false)?)
+                Some(self.infer_bin_ops(expr.location, left, *op, right, BinOpVariant::Normal)?)
             }
             ExprKind::UnaryOp { op, operand } => {
                 Some(self.infer_unary_ops(expr.location, *op, operand)?)
@@ -615,6 +618,7 @@ impl<'a> Inferencer<'a> {
         obj: Type,
         params: Vec<Type>,
         ret: Option<Type>,
+        call_info: CallInfo,
     ) -> InferenceResult {
         if let TypeEnum::TObj { params: class_params, fields, .. } = &*self.unifier.get_ty(obj) {
             if class_params.is_empty() {
@@ -628,6 +632,7 @@ impl<'a> Inferencer<'a> {
                                 ret: sign.ret,
                                 fun: RefCell::new(None),
                                 loc: Some(location),
+                                info: call_info,
                             };
                             if let Some(ret) = ret {
                                 self.unifier
@@ -642,14 +647,7 @@ impl<'a> Inferencer<'a> {
                                     })
                                     .unwrap();
                             }
-                            let required: Vec<_> = sign
-                                .args
-                                .iter()
-                                .filter(|v| v.default_value.is_none())
-                                .map(|v| v.name)
-                                .rev()
-                                .collect();
-                            self.unifier.unify_call(&call, ty, sign, &required).map_err(|e| {
+                            self.unifier.unify_call(&call, ty, sign).map_err(|e| {
                                 HashSet::from([e
                                     .at(Some(location))
                                     .to_display(self.unifier)
@@ -669,6 +667,7 @@ impl<'a> Inferencer<'a> {
             ret,
             fun: RefCell::new(None),
             loc: Some(location),
+            info: call_info,
         });
         self.calls.insert(location.into(), call);
         let call = self.unifier.add_ty(TypeEnum::TCall(vec![call]));
@@ -1346,17 +1345,11 @@ impl<'a> Inferencer<'a> {
                     fun: RefCell::new(None),
                     ret: sign.ret,
                     loc: Some(location),
+                    info: CallInfo::IsNormalFunctionCall,
                 };
-                let required: Vec<_> = sign
-                    .args
-                    .iter()
-                    .filter(|v| v.default_value.is_none())
-                    .map(|v| v.name)
-                    .rev()
-                    .collect();
-                self.unifier.unify_call(&call, func.custom.unwrap(), sign, &required).map_err(
-                    |e| HashSet::from([e.at(Some(location)).to_display(self.unifier).to_string()]),
-                )?;
+                self.unifier.unify_call(&call, func.custom.unwrap(), sign).map_err(|e| {
+                    HashSet::from([e.at(Some(location)).to_display(self.unifier).to_string()])
+                })?;
                 return Ok(Located {
                     location,
                     custom: Some(sign.ret),
@@ -1375,6 +1368,7 @@ impl<'a> Inferencer<'a> {
             fun: RefCell::new(None),
             ret,
             loc: Some(location),
+            info: CallInfo::IsNormalFunctionCall,
         });
         self.calls.insert(location.into(), call);
         let call = self.unifier.add_ty(TypeEnum::TCall(vec![call]));
@@ -1550,7 +1544,7 @@ impl<'a> Inferencer<'a> {
         left: &ast::Expr<Option<Type>>,
         op: ast::Operator,
         right: &ast::Expr<Option<Type>>,
-        is_aug_assign: bool,
+        variant: BinOpVariant,
     ) -> InferenceResult {
         let left_ty = left.custom.unwrap();
         let right_ty = right.custom.unwrap();
@@ -1558,27 +1552,39 @@ impl<'a> Inferencer<'a> {
         let method = if let TypeEnum::TObj { fields, .. } =
             self.unifier.get_ty_immutable(left_ty).as_ref()
         {
-            let (binop_name, binop_assign_name) =
-                (binop_name(op).into(), binop_assign_name(op).into());
+            let normal_method_name = OpInfo::from_binop(op, BinOpVariant::Normal).method_name;
+            let assign_method_name = OpInfo::from_binop(op, BinOpVariant::AugAssign).method_name;
+
             // if is aug_assign, try aug_assign operator first
-            if is_aug_assign && fields.contains_key(&binop_assign_name) {
-                binop_assign_name
+            if variant == BinOpVariant::AugAssign && fields.contains_key(&assign_method_name.into())
+            {
+                assign_method_name
             } else {
-                binop_name
+                normal_method_name
             }
         } else {
-            binop_name(op).into()
+            OpInfo::from_binop(op, variant).method_name
         };
 
-        let ret = if is_aug_assign {
-            // The type of augmented assignment operator should never change
-            Some(left_ty)
-        } else {
-            typeof_binop(self.unifier, self.primitives, op, left_ty, right_ty)
-                .map_err(|e| HashSet::from([format!("{e} (at {location})")]))?
+        let ret = match variant {
+            BinOpVariant::Normal => {
+                typeof_binop(self.unifier, self.primitives, op, left_ty, right_ty)
+                    .map_err(|e| HashSet::from([format!("{e} (at {location})")]))?
+            }
+            BinOpVariant::AugAssign => {
+                // The type of augmented assignment operator should never change
+                Some(left_ty)
+            }
         };
 
-        self.build_method_call(location, method, left_ty, vec![right_ty], ret)
+        self.build_method_call(
+            location,
+            method.into(),
+            left_ty,
+            vec![right_ty],
+            ret,
+            CallInfo::IsBinaryOp { self_type: left.custom.unwrap(), operator: op, variant },
+        )
     }
 
     fn infer_unary_ops(
@@ -1587,12 +1593,19 @@ impl<'a> Inferencer<'a> {
         op: ast::Unaryop,
         operand: &ast::Expr<Option<Type>>,
     ) -> InferenceResult {
-        let method = unaryop_name(op).into();
+        let method = OpInfo::from_unaryop(op).method_name.into();
 
         let ret = typeof_unaryop(self.unifier, self.primitives, op, operand.custom.unwrap())
             .map_err(|e| HashSet::from([format!("{e} (at {location})")]))?;
 
-        self.build_method_call(location, method, operand.custom.unwrap(), vec![], ret)
+        self.build_method_call(
+            location,
+            method,
+            operand.custom.unwrap(),
+            vec![],
+            ret,
+            CallInfo::IsUnaryOp { self_type: operand.custom.unwrap(), operator: op },
+        )
     }
 
     fn infer_compare(
@@ -1617,8 +1630,9 @@ impl<'a> Inferencer<'a> {
 
         let mut res = None;
         for (a, b, c) in izip!(once(left).chain(comparators), comparators, ops) {
-            let method = comparison_name(*c)
+            let method = OpInfo::from_cmpop(*c)
                 .ok_or_else(|| HashSet::from(["unsupported comparator".to_string()]))?
+                .method_name
                 .into();
 
             let ret = typeof_cmpop(
@@ -1636,6 +1650,7 @@ impl<'a> Inferencer<'a> {
                 a.custom.unwrap(),
                 vec![b.custom.unwrap()],
                 ret,
+                CallInfo::IsComparisonOp { self_type: left.custom.unwrap(), operator: *c },
             )?);
         }
 

nac3core/src/typecheck/typedef/mod.rs

@@ -8,12 +8,14 @@ use std::rc::Rc;
 use std::sync::{Arc, Mutex};
 use std::{borrow::Cow, collections::HashSet};
 
-use nac3parser::ast::{Location, StrRef};
+use nac3parser::ast::{Cmpop, Location, Operator, StrRef, Unaryop};
 
+use super::magic_methods::BinOpVariant;
 use super::type_error::{TypeError, TypeErrorKind};
 use super::unification_table::{UnificationKey, UnificationTable};
 use crate::symbol_resolver::SymbolValue;
 use crate::toplevel::{DefinitionId, TopLevelContext, TopLevelDef};
+use crate::typecheck::magic_methods::OpInfo;
 use crate::typecheck::type_inferencer::PrimitiveStore;
 
 #[cfg(test)]
@@ -73,6 +75,32 @@ pub fn iter_type_vars(var_map: &VarMap) -> impl Iterator<Item = TypeVar> + '_ {
     var_map.iter().map(|(&id, &ty)| TypeVar { id, ty })
 }
 
+/// Extra details about how a [`Call`] was written by the user.
+#[derive(Debug, Clone)]
+pub enum CallInfo {
+    /// The call was written as an unary operation, e.g., `~a` or `not a`.
+    IsUnaryOp {
+        /// The [`Type`] of the `self` object
+        self_type: Type,
+        operator: Unaryop,
+    },
+    /// The call was written as a binary operation, e.g., `a + b` or `a += b`.
+    IsBinaryOp {
+        /// The [`Type`] of the `self` object
+        self_type: Type,
+        operator: Operator,
+        variant: BinOpVariant,
+    },
+    /// The call was written as a binary comparison operation, e.g., `a < b`.
+    IsComparisonOp {
+        /// The [`Type`] of the `self` object
+        self_type: Type,
+        operator: Cmpop,
+    },
+    /// "Normal" function calls that looks like `func(1, 2, 3)`.
+    IsNormalFunctionCall,
+}
+
 #[derive(Clone)]
 pub struct Call {
     pub posargs: Vec<Type>,
@@ -80,6 +108,7 @@ pub struct Call {
     pub ret: Type,
     pub fun: RefCell<Option<Type>>,
     pub loc: Option<Location>,
+    pub info: CallInfo,
 }
 
 #[derive(Debug, Clone)]
@@ -89,6 +118,13 @@ pub struct FuncArg {
     pub default_value: Option<SymbolValue>,
 }
 
+impl FuncArg {
+    #[must_use]
+    pub fn is_required(&self) -> bool {
+        self.default_value.is_none()
+    }
+}
+
 #[derive(Debug, Clone)]
 pub struct FunSignature {
     pub args: Vec<FuncArg>,
@@ -562,69 +598,230 @@ impl Unifier {
         call: &Call,
         b: Type,
         signature: &FunSignature,
-        required: &[StrRef],
     ) -> Result<(), TypeError> {
+        /*
+            NOTE: scenarios to consider:
+
+            ```python
+            def func1(x: int32, y: int32, z: int32 = 5): pass
+
+            # Normal scenarios
+            func1(23, 45) # OK, z has default
+            func1(23, 45, 67) # OK, z's default is overwritten
+            func1(x = 23, y = 45) # OK, user is using kwargs to set positional args
+            func1(y = 45, x = 23) # OK, kwargs order doesn't matter
+
+            # Error scenarios
+            func1() # ERROR: Missing arguments: x, y
+            func1(23) # ERROR: Missing arguments: y
+            func1(z = 23) # ERROR: Missing arguments: x, y
+            func1(x = 23) # ERROR: Missing arguments: y
+            func1(23, 45, x = 5) # ERROR: Got multiple values for x
+            func1(23, 45, x = 5, y = 6) # ERROR: Got multiple values for x (y too but Python does not report it)
+            func1(23, 45, 67, z = 89) # ERROR: Got multiple values for z
+            func1(23, 45, 67, 89) # ERROR: Function only takes from 2 to 3 positional arguments but 4 were given.
+            func1(23, 45, 67, w = 3) # ERROR: Got an unexpected keyword argument 'w'
+
+            # Error scenarios that do not need to be handled here.
+            func1(23, 45, z = 67, z = 89) # ERROR: Keyword argument repeated: z, the parser panics on this.
+            ```
+        */
+
+        struct ParamInfo<'a> {
+            /// Has this parameter been supplied with an argument already?
+            has_been_supplied: bool,
+            /// The corresponding [`FuncArg`] instance of this parameter (for fast table lookups)
+            param: &'a FuncArg,
+        }
+
         let snapshot = self.unification_table.get_snapshot();
         if self.snapshot.is_none() {
             self.snapshot = Some(snapshot);
         }
 
-        let Call { posargs, kwargs, ret, fun, loc } = call;
-        let instantiated = self.instantiate_fun(b, signature);
-        let r = self.get_ty(instantiated);
-        let r = r.as_ref();
-        let TypeEnum::TFunc(signature) = r 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.to_vec();
-        let mut all_names: Vec<_> = signature.args.iter().map(|v| (v.name, v.ty)).rev().collect();
-        for (i, t) in posargs.iter().enumerate() {
-            if signature.args.len() <= i {
-                self.restore_snapshot();
-                return Err(TypeError::new(
-                    TypeErrorKind::TooManyArguments {
-                        expected: signature.args.len(),
-                        got: posargs.len() + kwargs.len(),
-                    },
-                    *loc,
-                ));
+        // Get details about the function signature/parameters.
+        let num_params = signature.args.len();
+
+        // Force the type vars in `b` and `signature' to be up-to-date.
+        let b = self.instantiate_fun(b, signature);
+        let TypeEnum::TFunc(signature) = &*self.get_ty(b) else { unreachable!() };
+
+        // Get details about the input arguments
+        let Call { posargs, kwargs, ret, fun, loc, info: call_info } = call;
+        let num_args = posargs.len() + kwargs.len();
+
+        // Now we check the arguments against the parameters,
+        // and depending on what `call_info` is, we might change how the behavior `unify_call()`
+        // in hopes to improve user error messages when type checking fails.
+        match call_info {
+            CallInfo::IsBinaryOp { self_type, operator, variant } => {
+                // The call is written in the form of (say) `a + b`.
+                // Technically, it is `a.__add__(b)`, and they have the following constraints:
+                assert_eq!(posargs.len(), 1);
+                assert_eq!(kwargs.len(), 0);
+                assert_eq!(num_params, 1);
+
+                let other_type = posargs[0]; // the second operand
+                let expected_other_type = signature.args[0].ty;
+
+                let ok = self.unify_impl(expected_other_type, other_type, false).is_ok();
+                if !ok {
+                    self.restore_snapshot();
+                    return Err(TypeError::new(
+                        TypeErrorKind::UnsupportedBinaryOpTypes {
+                            operator: *operator,
+                            variant: *variant,
+                            lhs_type: *self_type,
+                            rhs_type: other_type,
+                            expected_rhs_type: expected_other_type,
+                        },
+                        *loc,
+                    ));
+                }
             }
-            required.pop();
-            let (name, expected) = all_names.pop().unwrap();
-            self.unify_impl(expected, *t, false).map_err(|_| {
-                self.restore_snapshot();
-                TypeError::new(TypeErrorKind::IncorrectArgType { name, expected, got: *t }, *loc)
-            })?;
-        }
-        for (k, t) in kwargs {
-            if let Some(i) = required.iter().position(|v| v == k) {
-                required.remove(i);
+            CallInfo::IsComparisonOp { self_type, operator }
+                if OpInfo::from_cmpop(*operator).is_some() // Otherwise that comparison operator is not supported.
+                =>
+            {
+                // The call is written in the form of (say) `a <= b`.
+                // Technically, it is `a.__le__(b)`, and they have the following constraints:
+                assert_eq!(posargs.len(), 1);
+                assert_eq!(kwargs.len(), 0);
+                assert_eq!(num_params, 1);
+
+                let other_type = posargs[0]; // the second operand
+                let expected_other_type = signature.args[0].ty;
+
+                let ok = self.unify_impl(expected_other_type, other_type, false).is_ok();
+                if !ok {
+                    self.restore_snapshot();
+                    return Err(TypeError::new(
+                        TypeErrorKind::UnsupportedComparsionOpTypes {
+                            operator: *operator,
+                            lhs_type: *self_type,
+                            rhs_type: other_type,
+                            expected_rhs_type: expected_other_type,
+                        },
+                        *loc,
+                    ));
+                }
             }
-            let i = all_names.iter().position(|v| &v.0 == k).ok_or_else(|| {
-                self.restore_snapshot();
-                TypeError::new(TypeErrorKind::UnknownArgName(*k), *loc)
-            })?;
-            let (name, expected) = all_names.remove(i);
-            self.unify_impl(expected, *t, false).map_err(|_| {
-                self.restore_snapshot();
-                TypeError::new(TypeErrorKind::IncorrectArgType { name, expected, got: *t }, *loc)
-            })?;
-        }
-        if !required.is_empty() {
-            self.restore_snapshot();
-            return Err(TypeError::new(
-                TypeErrorKind::MissingArgs(required.iter().join(", ")),
-                *loc,
-            ));
-        }
-        self.unify_impl(*ret, signature.ret, false).map_err(|mut err| {
-            self.restore_snapshot();
-            if err.loc.is_none() {
-                err.loc = *loc;
+            _ => {
+                // Handle [`CallInfo::IsNormalFunctionCall`] and other uninteresting variants
+                // of [`CallInfo`] (e.g, `CallInfo::IsUnaryOp` and unsupported comparison operators)
+
+                // Helper lambdas
+                let mut type_check_arg = |param_name, expected_arg_ty, arg_ty| {
+                    let ok = self.unify_impl(expected_arg_ty, arg_ty, false).is_ok();
+                    if ok {
+                        Ok(())
+                    } else {
+                        // Typecheck failed, throw an error.
+                        self.restore_snapshot();
+                        Err(TypeError::new(
+                            TypeErrorKind::IncorrectArgType {
+                                name: param_name,
+                                expected: expected_arg_ty,
+                                got: arg_ty,
+                            },
+                            *loc,
+                        ))
+                    }
+                };
+
+                // Check for "too many arguments"
+                if num_params < posargs.len() {
+                    let expected_min_count =
+                        signature.args.iter().filter(|param| param.is_required()).count();
+                    let expected_max_count = num_params;
+
+                    self.restore_snapshot();
+                    return Err(TypeError::new(
+                        TypeErrorKind::TooManyArguments {
+                            expected_min_count,
+                            expected_max_count,
+                            got_count: num_args,
+                        },
+                        *loc,
+                    ));
+                }
+
+                // NOTE: order of `param_info_by_name` is leveraged, so use an IndexMap
+                let mut param_info_by_name: IndexMap<StrRef, ParamInfo> = signature
+                    .args
+                    .iter()
+                    .map(|arg| (arg.name, ParamInfo { has_been_supplied: false, param: arg }))
+                    .collect();
+
+                // Now consume all positional arguments and typecheck them.
+                for (&arg_ty, param) in zip(posargs, signature.args.iter()) {
+                    // We will also use this opportunity to mark the corresponding `param_info` as having been supplied.
+                    let param_info = param_info_by_name.get_mut(&param.name).unwrap();
+                    param_info.has_been_supplied = true;
+
+                    // Typecheck
+                    type_check_arg(param.name, param.ty, arg_ty)?;
+                }
+
+                // Now consume all keyword arguments and typecheck them.
+                for (&param_name, &arg_ty) in kwargs {
+                    // We will also use this opportunity to check if this keyword argument is "legal".
+
+                    let Some(param_info) = param_info_by_name.get_mut(&param_name) else {
+                        self.restore_snapshot();
+                        return Err(TypeError::new(
+                            TypeErrorKind::UnknownArgName(param_name),
+                            *loc,
+                        ));
+                    };
+
+                    if param_info.has_been_supplied {
+                        // NOTE: Duplicate keyword argument (i.e., `hello(1, 2, 3, arg = 4, arg = 5)`)
+                        // is IMPOSSIBLE as the parser would have already failed.
+                        // We only have to care about "got multiple values for XYZ"
+
+                        self.restore_snapshot();
+                        return Err(TypeError::new(
+                            TypeErrorKind::GotMultipleValues { name: param_name },
+                            *loc,
+                        ));
+                    }
+
+                    param_info.has_been_supplied = true;
+
+                    // Typecheck
+                    type_check_arg(param_name, param_info.param.ty, arg_ty)?;
+                }
+
+                // After checking posargs and kwargs, check if there are any
+                // unsupplied required parameters, and throw an error if they exist.
+                let missing_arg_names = param_info_by_name
+                    .values()
+                    .filter(|param_info| {
+                        param_info.param.is_required() && !param_info.has_been_supplied
+                    })
+                    .map(|param_info| param_info.param.name)
+                    .collect_vec();
+                if !missing_arg_names.is_empty() {
+                    self.restore_snapshot();
+                    return Err(TypeError::new(
+                        TypeErrorKind::MissingArgs { missing_arg_names },
+                        *loc,
+                    ));
+                }
+
+                // Finally, check the Call's return type
+                self.unify_impl(*ret, signature.ret, false).map_err(|mut err| {
+                    self.restore_snapshot();
+                    if err.loc.is_none() {
+                        err.loc = *loc;
+                    }
+                    err
+                })?;
             }
-            err
-        })?;
-        *fun.borrow_mut() = Some(instantiated);
+        }
+
+        *fun.borrow_mut() = Some(b);
 
         self.discard_snapshot(snapshot);
         Ok(())
@@ -990,17 +1187,10 @@ impl Unifier {
                 self.unification_table.set_value(b, Rc::new(TCall(calls)));
             }
             (TCall(calls), TFunc(signature)) => {
-                let required: Vec<StrRef> = signature
-                    .args
-                    .iter()
-                    .filter(|v| v.default_value.is_none())
-                    .map(|v| v.name)
-                    .rev()
-                    .collect();
                 // we unify every calls to the function signature.
                 for c in calls {
                     let call = self.calls[c.0].clone();
-                    self.unify_call(&call, b, signature, &required)?;
+                    self.unify_call(&call, b, signature)?;
                 }
                 self.set_a_to_b(a, b);
             }