fix comment in let-else test

Author: cormacrelf

src/test/ui/let-else/let-else-deref-coercion.rs

@@ -1,7 +1,7 @@
 // Taken from https://github.com/rust-lang/rust/blob/6cc0a764e082d9c0abcf37a768d5889247ba13e2/compiler/rustc_typeck/src/check/_match.rs#L445-L462
 //
-// We attempt to `let Bar::Present(_) = foo` where foo is meant to Deref/DerefMut to Bar. You can do
-// this with an irrefutable binding, so it should work with let-else too.
+// We attempt to `let Bar::Present(_): &mut Bar = foo` where foo is meant to Deref/DerefMut to Bar.
+// You can do this with an irrefutable binding, so it should work with let-else too.
 
 #![feature(let_else)]
 use std::ops::{Deref, DerefMut};