Test new placeholder error messages in previously untested combinations

Author: lqd

src/test/ui/issues/issue-57362.rs

@@ -0,0 +1,41 @@
+// Test for issue #57362, ensuring that the self ty is shown in cases of higher-ranked lifetimes
+// conflicts: the `expected` and `found` trait refs would otherwise be printed the same, leading
+// to confusing notes such as:
+//  = note: expected type `Trait`
+//             found type `Trait`
+
+// from issue #57362
+trait Trait {
+    fn f(self);
+}
+
+impl<T> Trait for fn(&T) {
+    fn f(self) {
+        println!("f");
+    }
+}
+
+fn f() {
+    let a: fn(_) = |_: &u8| {};
+    a.f(); //~ ERROR not general enough
+}
+
+// extracted from a similar issue: #57642
+trait X {
+    type G;
+    fn make_g() -> Self::G;
+}
+
+impl<'a> X for fn(&'a ()) {
+    type G = &'a ();
+
+    fn make_g() -> Self::G {
+        &()
+    }
+}
+
+fn g() {
+    let x = <fn (&())>::make_g(); //~ ERROR not general enough
+}
+
+fn main() {}

src/test/ui/issues/issue-57362.stderr

@@ -0,0 +1,20 @@
+error: implementation of `Trait` is not general enough
+  --> $DIR/issue-57362.rs:20:7
+   |
+LL |     a.f(); //~ ERROR not general enough
+   |       ^
+   |
+   = note: `Trait` would have to be implemented for the type `fn(&u8)`
+   = note: but `Trait` is actually implemented for the type `for<'r> fn(&'r u8)`
+
+error: implementation of `X` is not general enough
+  --> $DIR/issue-57362.rs:38:13
+   |
+LL |     let x = <fn (&())>::make_g(); //~ ERROR not general enough
+   |             ^^^^^^^^^^^^^^^^^^
+   |
+   = note: `X` would have to be implemented for the type `for<'r> fn(&'r ())`
+   = note: but `X` is actually implemented for the type `fn(&'0 ())`, for the specific lifetime `'0`
+
+error: aborting due to 2 previous errors
+