Merge #1694

1694: Implement initial type-inference support for Index r=flodiebold a=matklad

This doesn't actually infer indexing types, but at least it walks sub-expressions!

Initially, I wanted to make `Index` just a new kind of `BinOp` (b/c indexing is kind of a binary op), so I've refactoring binop handing a bit.

However, in the end I've decided to add a separate expr kind for Index, because `foo[0]`, `&foo[1]` and `&mut foo[1]` all seem to need slightly different handing, which is not binop-like

r? @flodiebold 

Co-authored-by: Aleksey Kladov <[email protected]>

1 files changed, 7 insertions, 3 deletions

diff --git a/crates/ra_hir/src/ty/infer.rs b/crates/ra_hir/src/ty/infer.rs
index 675df4a22..cca59538a 100644
--- a/crates/ra_hir/src/ty/infer.rs
+++ b/crates/ra_hir/src/ty/infer.rs
@@ -1265,9 +1265,7 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
             Expr::BinaryOp { lhs, rhs, op } => match op {
                 Some(op) => {
                     let lhs_expectation = match op {
-                        BinaryOp::BooleanAnd | BinaryOp::BooleanOr => {
-                            Expectation::has_type(Ty::simple(TypeCtor::Bool))
-                        }
+                        BinaryOp::LogicOp(..) => Expectation::has_type(Ty::simple(TypeCtor::Bool)),
                         _ => Expectation::none(),
                     };
                     let lhs_ty = self.infer_expr(*lhs, &lhs_expectation);
@@ -1281,6 +1279,12 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
                 }
                 _ => Ty::Unknown,
             },
+            Expr::Index { base, index } => {
+                let _base_ty = self.infer_expr(*base, &Expectation::none());
+                let _index_ty = self.infer_expr(*index, &Expectation::none());
+                // FIXME: use `std::ops::Index::Output` to figure out the real return type
+                Ty::Unknown
+            }
             Expr::Tuple { exprs } => {
                 let mut ty_vec = Vec::with_capacity(exprs.len());
                 for arg in exprs.iter() {