X-Git-Url: https://git.lizzy.rs/?a=blobdiff_plain;f=compiler%2Frustc_hir_typeck%2Fsrc%2Fcallee.rs;h=b09ddf80e2a52577292e3d602fca7e3cff198dc2;hb=552b63c1619498f1a17fd482f4bb87815d8fdc48;hp=1c14c1d35f7997ef026f08ed22134a100f6ae75f;hpb=5c2592cd4324973b48011a8a93908612bec9cebf;p=rust.git

diff --git a/compiler/rustc_hir_typeck/src/callee.rs b/compiler/rustc_hir_typeck/src/callee.rs
index 1c14c1d35f7..b09ddf80e2a 100644
--- a/compiler/rustc_hir_typeck/src/callee.rs
+++ b/compiler/rustc_hir_typeck/src/callee.rs
@@ -179,12 +179,16 @@ fn try_overloaded_call_step(
 
             // Hack: we know that there are traits implementing Fn for &F
             // where F:Fn and so forth. In the particular case of types
-            // like `x: &mut FnMut()`, if there is a call `x()`, we would
-            // normally translate to `FnMut::call_mut(&mut x, ())`, but
-            // that winds up requiring `mut x: &mut FnMut()`. A little
-            // over the top. The simplest fix by far is to just ignore
-            // this case and deref again, so we wind up with
-            // `FnMut::call_mut(&mut *x, ())`.
+            // like `f: &mut FnMut()`, if there is a call `f()`, we would
+            // normally translate to `FnMut::call_mut(&mut f, ())`, but
+            // that winds up potentially requiring the user to mark their
+            // variable as `mut` which feels unnecessary and unexpected.
+            //
+            //     fn foo(f: &mut impl FnMut()) { f() }
+            //            ^ without this hack `f` would have to be declared as mutable
+            //
+            // The simplest fix by far is to just ignore this case and deref again,
+            // so we wind up with `FnMut::call_mut(&mut *f, ())`.
             ty::Ref(..) if autoderef.step_count() == 0 => {
                 return None;
             }
@@ -444,7 +448,7 @@ fn confirm_builtin_call(
         // previously appeared within a `Binder<>` and hence would not
         // have been normalized before.
         let fn_sig = self.replace_bound_vars_with_fresh_vars(call_expr.span, infer::FnCall, fn_sig);
-        let fn_sig = self.normalize_associated_types_in(call_expr.span, fn_sig);
+        let fn_sig = self.normalize(call_expr.span, fn_sig);
 
         // Call the generic checker.
         let expected_arg_tys = self.expected_inputs_for_expected_output(