1 files changed, 58 insertions, 0 deletions

diff --git a/crates/hir_ty/src/op.rs b/crates/hir_ty/src/op.rs
new file mode 100644
index 000000000..0870874fc
--- /dev/null
+++ b/crates/hir_ty/src/op.rs
@@ -0,0 +1,58 @@
+//! Helper functions for binary operator type inference.
+use hir_def::expr::{ArithOp, BinaryOp, CmpOp};
+
+use super::{InferTy, Ty, TypeCtor};
+use crate::ApplicationTy;
+
+pub(super) fn binary_op_return_ty(op: BinaryOp, lhs_ty: Ty, rhs_ty: Ty) -> Ty {
+    match op {
+        BinaryOp::LogicOp(_) | BinaryOp::CmpOp(_) => Ty::simple(TypeCtor::Bool),
+        BinaryOp::Assignment { .. } => Ty::unit(),
+        BinaryOp::ArithOp(ArithOp::Shl) | BinaryOp::ArithOp(ArithOp::Shr) => match lhs_ty {
+            Ty::Apply(ApplicationTy { ctor, .. }) => match ctor {
+                TypeCtor::Int(..) | TypeCtor::Float(..) => lhs_ty,
+                _ => Ty::Unknown,
+            },
+            Ty::Infer(InferTy::IntVar(..)) | Ty::Infer(InferTy::FloatVar(..)) => lhs_ty,
+            _ => Ty::Unknown,
+        },
+        BinaryOp::ArithOp(_) => match rhs_ty {
+            Ty::Apply(ApplicationTy { ctor, .. }) => match ctor {
+                TypeCtor::Int(..) | TypeCtor::Float(..) => rhs_ty,
+                _ => Ty::Unknown,
+            },
+            Ty::Infer(InferTy::IntVar(..)) | Ty::Infer(InferTy::FloatVar(..)) => rhs_ty,
+            _ => Ty::Unknown,
+        },
+    }
+}
+
+pub(super) fn binary_op_rhs_expectation(op: BinaryOp, lhs_ty: Ty) -> Ty {
+    match op {
+        BinaryOp::LogicOp(..) => Ty::simple(TypeCtor::Bool),
+        BinaryOp::Assignment { op: None } => lhs_ty,
+        BinaryOp::CmpOp(CmpOp::Eq { .. }) => match lhs_ty {
+            Ty::Apply(ApplicationTy { ctor, .. }) => match ctor {
+                TypeCtor::Int(..)
+                | TypeCtor::Float(..)
+                | TypeCtor::Str
+                | TypeCtor::Char
+                | TypeCtor::Bool => lhs_ty,
+                _ => Ty::Unknown,
+            },
+            Ty::Infer(InferTy::IntVar(..)) | Ty::Infer(InferTy::FloatVar(..)) => lhs_ty,
+            _ => Ty::Unknown,
+        },
+        BinaryOp::ArithOp(ArithOp::Shl) | BinaryOp::ArithOp(ArithOp::Shr) => Ty::Unknown,
+        BinaryOp::CmpOp(CmpOp::Ord { .. })
+        | BinaryOp::Assignment { op: Some(_) }
+        | BinaryOp::ArithOp(_) => match lhs_ty {
+            Ty::Apply(ApplicationTy { ctor, .. }) => match ctor {
+                TypeCtor::Int(..) | TypeCtor::Float(..) => lhs_ty,
+                _ => Ty::Unknown,
+            },
+            Ty::Infer(InferTy::IntVar(..)) | Ty::Infer(InferTy::FloatVar(..)) => lhs_ty,
+            _ => Ty::Unknown,
+        },
+    }
+}