add a regression test for issue 153599

Author: TaKO8Ki

tests/ui/delegation/generics/stability-implications-non-local-defid.rs

@@ -0,0 +1,21 @@
+//@ check-pass
+
+#![feature(fn_delegation)]
+#![allow(incomplete_features)]
+#![feature(staged_api)]
+#![unstable(feature = "foo", issue = "none")]
+
+pub mod m {
+    #[unstable(feature = "foo", issue = "none")]
+    pub struct W<I, F> {
+        pub inner: std::iter::Map<I, F>,
+    }
+
+    #[unstable(feature = "foo", issue = "none")]
+    impl<B, I: Iterator, F: FnMut(I::Item) -> B> Iterator for W<I, F> {
+        type Item = B;
+        reuse Iterator::{next, fold} { self.inner }
+    }
+}
+
+fn main() {}