Add known-bug directive to issue #47511 test case

Author: marmeladema

src/test/ui/issues/issue-47511.rs

@@ -1,14 +1,15 @@
+// check-fail
+// known-bug
+
 // Regression test for #47511: anonymous lifetimes can appear
 // unconstrained in a return type, but only if they appear just once
 // in the input, as the input to a projection.
 
 fn f(_: X) -> X {
-    //~^ ERROR return type references an anonymous lifetime
     unimplemented!()
 }
 
 fn g<'a>(_: X<'a>) -> X<'a> {
-    //~^ ERROR return type references lifetime `'a`, which is not constrained
     unimplemented!()
 }
 

src/test/ui/issues/issue-47511.stderr

@@ -1,13 +1,13 @@
 error[E0581]: return type references an anonymous lifetime, which is not constrained by the fn input types
-  --> $DIR/issue-47511.rs:5:15
+  --> $DIR/issue-47511.rs:8:15
    |
 LL | fn f(_: X) -> X {
    |               ^
    |
    = note: lifetimes appearing in an associated type are not considered constrained
 
 error[E0581]: return type references lifetime `'a`, which is not constrained by the fn input types
-  --> $DIR/issue-47511.rs:10:23
+  --> $DIR/issue-47511.rs:12:23
    |
 LL | fn g<'a>(_: X<'a>) -> X<'a> {
    |                       ^^^^^