From 5fe220b9873d587188adae63fa205481a9aae9ce Mon Sep 17 00:00:00 2001
From: Florian Diebold <flodiebold@gmail.com>
Date: Sat, 29 Feb 2020 15:31:07 +0100
Subject: Fix a common false-positive type mismatch

E.g. for `&{ some_string() }` in a context where a `&str` is expected, we
reported a mismatch inside the block. The problem is that we're passing an
expectation of `str` down, but the expectation is more of a hint in this case.
There's a long comment in rustc about this, which I just copied.

Also, fix reported location for type mismatches in macros.
---
 crates/ra_hir_ty/src/infer/expr.rs | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

(limited to 'crates/ra_hir_ty/src/infer')

diff --git a/crates/ra_hir_ty/src/infer/expr.rs b/crates/ra_hir_ty/src/infer/expr.rs
index 9d5f75625..3db5b2b51 100644
--- a/crates/ra_hir_ty/src/infer/expr.rs
+++ b/crates/ra_hir_ty/src/infer/expr.rs
@@ -42,14 +42,14 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
     /// Return the type after possible coercion.
     pub(super) fn infer_expr_coerce(&mut self, expr: ExprId, expected: &Expectation) -> Ty {
         let ty = self.infer_expr_inner(expr, &expected);
-        let ty = if !self.coerce(&ty, &expected.ty) {
+        let ty = if !self.coerce(&ty, &expected.coercion_target()) {
             self.result
                 .type_mismatches
                 .insert(expr, TypeMismatch { expected: expected.ty.clone(), actual: ty.clone() });
             // Return actual type when type mismatch.
             // This is needed for diagnostic when return type mismatch.
             ty
-        } else if expected.ty == Ty::Unknown {
+        } else if expected.coercion_target() == &Ty::Unknown {
             ty
         } else {
             expected.ty.clone()
@@ -297,7 +297,7 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
                             // FIXME: throw type error - expected mut reference but found shared ref,
                             // which cannot be coerced
                         }
-                        Expectation::has_type(Ty::clone(exp_inner))
+                        Expectation::rvalue_hint(Ty::clone(exp_inner))
                     } else {
                         Expectation::none()
                     };
@@ -542,7 +542,7 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
         let ty = if let Some(expr) = tail {
             self.infer_expr_coerce(expr, expected)
         } else {
-            self.coerce(&Ty::unit(), &expected.ty);
+            self.coerce(&Ty::unit(), expected.coercion_target());
             Ty::unit()
         };
         if diverges {
-- 
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