Add regression test

Author: oli-obk

tests/incremental/rpitit-feeding.rs

@@ -0,0 +1,22 @@
+// revisions: cpass cpass2
+
+// This test checks that creating a new `DefId` from within a query `A`
+// recreates that `DefId` before reexecuting queries that depend on query `A`.
+// Otherwise we'd end up referring to a `DefId` that doesn't exist.
+// At present this is handled by always marking all queries as red if they create
+// a new `DefId` and thus subsequently rerunning the query.
+
+#![feature(return_position_impl_trait_in_trait)]
+#![allow(incomplete_features)]
+
+trait Foo {
+    fn foo() -> impl Sized;
+}
+
+impl Foo for String {
+    fn foo() -> i32 {
+        22
+    }
+}
+
+fn main() {}