Fix diagnostic by using predicate in GATs too

Author: tmandry

src/librustc_typeck/check/compare_method.rs

@@ -1220,11 +1220,7 @@ fn compare_projection_bounds<'tcx>(
     // we want <T as X>::Y to normalize to S. This is valid because we are
     // checking the default value specifically here. Add this equality to the
     // ParamEnv for normalization specifically.
-    let normalize_param_env = if impl_ty.defaultness.is_final() {
-        // If the associated type is final then normalization can already
-        // do this without the explicit predicate.
-        param_env
-    } else {
+    let normalize_param_env = {
         let mut predicates = param_env.caller_bounds().iter().collect::<Vec<_>>();
         predicates.push(
             ty::Binder::dummy(ty::ProjectionPredicate {

src/test/ui/generic-associated-types/unsatisfied-outlives-bound.rs

@@ -7,7 +7,7 @@ trait ATy {
 
 impl<'b> ATy for &'b () {
     type Item<'a> = &'b ();
-    //~^ ERROR cannot infer an appropriate lifetime
+    //~^ ERROR does not fulfill the required lifetime
 }
 
 trait StaticTy {

src/test/ui/generic-associated-types/unsatisfied-outlives-bound.stderr

@@ -1,31 +1,14 @@
-error[E0495]: cannot infer an appropriate lifetime for lifetime parameter `'b` due to conflicting requirements
+error[E0477]: the type `&'b ()` does not fulfill the required lifetime
   --> $DIR/unsatisfied-outlives-bound.rs:9:5
    |
 LL |     type Item<'a> = &'b ();
    |     ^^^^^^^^^^^^^^^^^^^^^^^
    |
-note: first, the lifetime cannot outlive the lifetime `'b` as defined on the impl at 8:6...
-  --> $DIR/unsatisfied-outlives-bound.rs:8:6
-   |
-LL | impl<'b> ATy for &'b () {
-   |      ^^
-note: ...so that the types are compatible
-  --> $DIR/unsatisfied-outlives-bound.rs:9:5
-   |
-LL |     type Item<'a> = &'b ();
-   |     ^^^^^^^^^^^^^^^^^^^^^^^
-   = note: expected `ATy`
-              found `ATy`
-note: but, the lifetime must be valid for the lifetime `'a` as defined on the associated item at 9:15...
+note: type must outlive the lifetime `'a` as defined on the associated item at 9:15
   --> $DIR/unsatisfied-outlives-bound.rs:9:15
    |
 LL |     type Item<'a> = &'b ();
    |               ^^
-note: ...so that the type `&()` will meet its required lifetime bounds
-  --> $DIR/unsatisfied-outlives-bound.rs:9:5
-   |
-LL |     type Item<'a> = &'b ();
-   |     ^^^^^^^^^^^^^^^^^^^^^^^
 
 error[E0477]: the type `&'a ()` does not fulfill the required lifetime
   --> $DIR/unsatisfied-outlives-bound.rs:18:5
@@ -37,5 +20,4 @@ LL |     type Item<'a> = &'a ();
 
 error: aborting due to 2 previous errors
 
-Some errors have detailed explanations: E0477, E0495.
-For more information about an error, try `rustc --explain E0477`.
+For more information about this error, try `rustc --explain E0477`.