Add test for issue-69840

Author: JohnTitor

src/test/ui/impl-trait/issue-69840.rs

@@ -0,0 +1,16 @@
+// check-pass
+
+#![feature(impl_trait_in_bindings)]
+#![allow(incomplete_features)]
+
+struct A<'a>(&'a ());
+
+trait Trait<T> {}
+
+impl<T> Trait<T> for () {}
+
+pub fn foo<'a>() {
+    let _x: impl Trait<A<'a>> = ();
+}
+
+fn main() {}