core/magic_methods: Add typeof_*op

Used to determine the expected type of the binary operator with
primitive operands.

nac3core/src/typecheck/magic_methods.rs

@@ -1,3 +1,7 @@
+use std::cmp::max;
+use crate::symbol_resolver::SymbolValue;
+use crate::toplevel::helper::PRIMITIVE_DEF_IDS;
+use crate::toplevel::numpy::{make_ndarray_ty, unpack_ndarray_var_tys};
 use crate::typecheck::{
     type_inferencer::*,
     typedef::{FunSignature, FuncArg, Type, TypeEnum, Unifier, VarMap},
@@ -6,6 +10,7 @@ use nac3parser::ast::StrRef;
 use nac3parser::ast::{Cmpop, Operator, Unaryop};
 use std::collections::HashMap;
 use std::rc::Rc;
+use itertools::Itertools;
 
 #[must_use]
 pub fn binop_name(op: &Operator) -> &'static str {
@@ -293,6 +298,137 @@ pub fn impl_eq(unifier: &mut Unifier, store: &PrimitiveStore, ty: Type) {
     impl_cmpop(unifier, store, ty, ty, &[Cmpop::Eq, Cmpop::NotEq]);
 }
 
+/// Returns the expected return type of binary operations with at least one `ndarray` operand.
+pub fn typeof_ndarray_broadcast(
+    unifier: &mut Unifier,
+    primitives: &PrimitiveStore,
+    left: Type,
+    right: Type,
+) -> Result<Type, String> {
+    let is_left_ndarray = left.get_obj_id(unifier) == PRIMITIVE_DEF_IDS.ndarray;
+    let is_right_ndarray = right.get_obj_id(unifier) == PRIMITIVE_DEF_IDS.ndarray;
+
+    assert!(is_left_ndarray || is_right_ndarray);
+
+    if is_left_ndarray && is_right_ndarray {
+        // Perform broadcasting on two ndarray operands.
+
+        let (left_ty_dtype, left_ty_ndims) = unpack_ndarray_var_tys(unifier, left);
+        let (right_ty_dtype, right_ty_ndims) = unpack_ndarray_var_tys(unifier, right);
+
+        assert!(unifier.unioned(left_ty_dtype, right_ty_dtype));
+
+        let left_ty_ndims = match &*unifier.get_ty_immutable(left_ty_ndims) {
+            TypeEnum::TLiteral { values, .. } => values.clone(),
+            _ => unreachable!(),
+        };
+        let right_ty_ndims = match &*unifier.get_ty_immutable(right_ty_ndims) {
+            TypeEnum::TLiteral { values, .. } => values.clone(),
+            _ => unreachable!(),
+        };
+
+        let res_ndims = left_ty_ndims.into_iter()
+            .cartesian_product(right_ty_ndims.into_iter())
+            .map(|(left, right)| {
+                let left_val = u64::try_from(left).unwrap();
+                let right_val = u64::try_from(right).unwrap();
+
+                max(left_val, right_val)
+            })
+            .unique()
+            .map(|ndim| SymbolValue::U64(ndim))
+            .collect_vec();
+        let res_ndims = unifier.get_fresh_literal(res_ndims, None);
+
+        Ok(make_ndarray_ty(unifier, primitives, Some(left_ty_dtype), Some(res_ndims)))
+    } else {
+        let (ndarray_ty, scalar_ty) = if is_left_ndarray {
+            (left, right)
+        } else {
+            (right, left)
+        };
+
+        let (ndarray_ty_dtype, _) = unpack_ndarray_var_tys(unifier, ndarray_ty);
+
+        if !unifier.unioned(ndarray_ty_dtype, scalar_ty) {
+            let (expected_ty, actual_ty) = if is_left_ndarray {
+                (ndarray_ty_dtype, scalar_ty)
+            } else {
+                (scalar_ty, ndarray_ty_dtype)
+            };
+
+            Err(format!(
+                "Expected right-hand side operand to be {}, got {}",
+                unifier.stringify(expected_ty),
+                unifier.stringify(actual_ty),
+            ))
+        } else {
+            Ok(ndarray_ty)
+        }
+    }
+}
+
+/// Returns the return type given a binary operator and its primitive operands.
+pub fn typeof_binop(
+    unifier: &mut Unifier,
+    primitives: &PrimitiveStore,
+    op: &Operator,
+    lhs: Type,
+    rhs: Type,
+) -> Result<Option<Type>, String> {
+    let is_left_ndarray = lhs.get_obj_id(unifier) == PRIMITIVE_DEF_IDS.ndarray;
+    let is_right_ndarray = rhs.get_obj_id(unifier) == PRIMITIVE_DEF_IDS.ndarray;
+
+    Ok(Some(match op {
+        Operator::Add
+        | Operator::Sub
+        | Operator::Mult
+        | Operator::Mod
+        | Operator::FloorDiv => {
+            if is_left_ndarray || is_right_ndarray {
+                typeof_ndarray_broadcast(unifier, primitives, lhs, rhs)?
+            } else if unifier.unioned(lhs, rhs) {
+                lhs
+            } else {
+                return Ok(None)
+            }
+        }
+
+        Operator::MatMult => typeof_ndarray_broadcast(unifier, primitives, lhs, rhs)?,
+        Operator::Div => {
+            if is_left_ndarray || is_right_ndarray {
+                typeof_ndarray_broadcast(unifier, primitives, lhs, rhs)?
+            } else if unifier.unioned(lhs, rhs) {
+                primitives.float
+            } else {
+                return Ok(None)
+            }
+        }
+
+        Operator::Pow => {
+            if is_left_ndarray || is_right_ndarray {
+                typeof_ndarray_broadcast(unifier, primitives, lhs, rhs)?
+            } else if [primitives.int32, primitives.int64, primitives.uint32, primitives.uint64, primitives.float].into_iter().any(|ty| unifier.unioned(lhs, ty)) {
+                lhs
+            } else {
+                return Ok(None)
+            }
+        }
+
+        Operator::LShift
+        | Operator::RShift
+        | Operator::BitOr
+        | Operator::BitXor
+        | Operator::BitAnd => {
+            if unifier.unioned(lhs, rhs) {
+                lhs
+            } else {
+                return Ok(None)
+            }
+        }
+    }))
+}
+
 pub fn set_primitives_magic_methods(store: &PrimitiveStore, unifier: &mut Unifier) {
     let PrimitiveStore {
         int32: int32_t,