Add regression test for issue 100187

Author: spastorino

src/test/ui/impl-trait/issue-100187.rs

@@ -0,0 +1,12 @@
+// check-pass
+
+trait Trait<T> {
+    type Ty;
+}
+impl Trait<&u8> for () {
+    type Ty = ();
+}
+
+fn test<'a, 'b>() -> impl Trait<&'a u8, Ty = impl Sized + 'b> {}
+
+fn main() {}