Error on unconstrained lifetime in RPITIT

tests/ui/impl-trait/in-trait/unconstrained-lt.rs

@@ -0,0 +1,16 @@
+// [next] compile-flags: -Zlower-impl-trait-in-trait-to-assoc-ty
+// revisions: current next
+
+#![feature(return_position_impl_trait_in_trait)]
+
+trait Foo {
+    fn test() -> impl Sized;
+}
+
+impl<'a, T> Foo for T {
+    //~^ ERROR the lifetime parameter `'a` is not constrained by the impl trait, self type, or predicates
+
+    fn test() -> &'a () { &() }
+}
+
+fn main() {}