1 files changed, 53 insertions, 0 deletions
diff --git a/src/test/ui/higher-rank-trait-bounds/normalize-under-binder/issue-90950.rs b/src/test/ui/higher-rank-trait-bounds/normalize-under-binder/issue-90950.rs
new file mode 100644
index 000000000..ab9d9a7ce
--- /dev/null
+++ b/src/test/ui/higher-rank-trait-bounds/normalize-under-binder/issue-90950.rs
@@ -0,0 +1,53 @@
+// check-fail
+// known-bug: #90950
+
+trait Yokeable<'a>: 'static {
+    type Output: 'a;
+}
+
+
+trait IsCovariant<'a> {}
+
+struct Yoke<Y: for<'a> Yokeable<'a>> {
+    data: Y,
+}
+
+
+// impl<Y: for<'a> Yokeable<'a>> Yoke<Y> {
+//     fn project<Y2: for<'a> Yokeable<'a>>(
+//         &self,
+//         f: for<'a> fn(<Y as Yokeable<'a>>::Output, &'a (),
+//     ) -> <Y2 as Yokeable<'a>>::Output) -> Yoke<Y2> {
+//         unimplemented!()
+//     }
+// }
+
+fn upcast<Y>(x: Yoke<Y>) -> Yoke<Box<dyn IsCovariant<'static> + 'static>> where
+    Y: for<'a> Yokeable<'a>,
+    for<'a> <Y as Yokeable<'a>>::Output: IsCovariant<'a>
+    {
+    // x.project(|data, _| {
+    //     Box::new(data)
+    // })
+    unimplemented!()
+}
+
+
+impl<'a> Yokeable<'a> for Box<dyn IsCovariant<'static> + 'static> {
+    type Output = Box<dyn IsCovariant<'a> + 'a>;
+}
+
+// this impl is mostly an example and unnecessary for the pure repro
+use std::borrow::*;
+impl<'a, T: ToOwned + ?Sized> Yokeable<'a> for Cow<'static, T> {
+    type Output = Cow<'a, T>;
+}
+impl<'a, T: ToOwned + ?Sized> IsCovariant<'a> for Cow<'a, T> {}
+
+
+
+fn upcast_yoke(y: Yoke<Cow<'static, str>>) -> Yoke<Box<dyn IsCovariant<'static> + 'static>> {
+    upcast(y)
+}
+
+fn main() {}