Add regression test for associated type outlives bound at call site

tests/ui/associated-types/assoc-type-outlives-via-where-clause-63253.rs

@@ -0,0 +1,33 @@
+//! Regression test for <https://github.com/rust-lang/rust/issues/63253>.
+//!
+//! A `where Self::Ty: 'a` bound on the callee was not being used to prove the
+//! associated type outlives `'a` at the call site, so both of these calls used
+//! to fail with E0309 ("the associated type `<T as Trait<'_>>::Ty` may not live
+//! long enough").
+
+//@ check-pass
+
+#![allow(unused)]
+
+// The associated function is reached through a method-call path.
+trait Trait<'a> {
+    type Ty;
+    fn method(ty_ref: &'a Self::Ty) where Self::Ty: 'a {}
+}
+
+fn caller<'a, T: Trait<'a>>(arg: &'a T::Ty) where T::Ty: 'a {
+    T::method(arg)
+}
+
+// The same bound, reached through a free function instead.
+trait Trait2<'a> {
+    type Ty;
+}
+
+fn free_fn<'a, T: Trait2<'a>>(_arg: &'a T::Ty) where T::Ty: 'a {}
+
+fn free_fn_caller<'a, T: Trait2<'a>>(arg: &'a T::Ty) where T::Ty: 'a {
+    free_fn::<T>(arg)
+}
+
+fn main() {}