Fix unquoted projection types in label

Author: estebank

compiler/rustc_middle/src/ty/error.rs

@@ -195,7 +195,7 @@ impl<'tcx> TypeError<'tcx> {
             )
             .into(),
             ProjectionMismatched(ref values) => format!(
-                "expected {}, found {}",
+                "expected `{}`, found `{}`",
                 tcx.def_path_str(values.expected),
                 tcx.def_path_str(values.found)
             )

tests/ui/generic-associated-types/collections-project-default.stderr

@@ -5,7 +5,7 @@ LL | fn floatify_sibling<C>(ints: &C) -> <C as Collection<i32>>::Sibling<f32>
    |                                     ------------------------------------ expected `<C as Collection<i32>>::Sibling<f32>` because of return type
 ...
 LL |     res
-   |     ^^^ expected Collection::Sibling, found CollectionFamily::Member
+   |     ^^^ expected `Collection::Sibling`, found `CollectionFamily::Member`
    |
    = note: expected associated type `<C as Collection<i32>>::Sibling<f32>`
               found associated type `<<C as Collection<i32>>::Family as CollectionFamily>::Member<f32>`