Add test for issue-60473

Author: JohnTitor

src/test/ui/impl-trait/issue-60473.rs

@@ -0,0 +1,16 @@
+// Regression test for #60473
+
+#![feature(impl_trait_in_bindings)]
+#![allow(incomplete_features)]
+
+struct A<'a>(&'a ());
+
+trait Trait<T> {
+}
+
+impl<T> Trait<T> for () {
+}
+
+fn main() {
+    let x: impl Trait<A> = (); //~ ERROR: opaque type expands to a recursive type
+}

src/test/ui/impl-trait/issue-60473.stderr

@@ -0,0 +1,11 @@
+error[E0720]: opaque type expands to a recursive type
+  --> $DIR/issue-60473.rs:15:12
+   |
+LL |     let x: impl Trait<A> = ();
+   |            ^^^^^^^^^^^^^ expands to a recursive type
+   |
+   = note: type resolves to itself
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0720`.