1 files changed, 50 insertions, 0 deletions

diff --git a/crates/ra_hir_ty/src/op.rs b/crates/ra_hir_ty/src/op.rs
new file mode 100644
index 000000000..09c47a76d
--- /dev/null
+++ b/crates/ra_hir_ty/src/op.rs
@@ -0,0 +1,50 @@
+//! FIXME: write short doc here
+use hir_def::expr::{BinaryOp, CmpOp};
+
+use super::{InferTy, Ty, TypeCtor};
+use crate::ApplicationTy;
+
+pub(super) fn binary_op_return_ty(op: BinaryOp, rhs_ty: Ty) -> Ty {
+    match op {
+        BinaryOp::LogicOp(_) | BinaryOp::CmpOp(_) => Ty::simple(TypeCtor::Bool),
+        BinaryOp::Assignment { .. } => Ty::unit(),
+        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 } | BinaryOp::CmpOp(CmpOp::Eq { negated: _ }) => {
+            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::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,
+        },
+    }
+}