1 files changed, 52 insertions, 0 deletions

diff --git a/tests/ui/issues/issue-55731.rs b/tests/ui/issues/issue-55731.rs
new file mode 100644
index 00000000000..7b4f4e2cd3b
--- /dev/null
+++ b/tests/ui/issues/issue-55731.rs
@@ -0,0 +1,52 @@
+use std::marker::PhantomData;
+
+trait DistributedIterator {
+    fn reduce(self)
+    where
+        Self: Sized,
+    {
+        unreachable!()
+    }
+}
+
+trait DistributedIteratorMulti<Source> {
+    type Item;
+}
+
+struct Connect<I>(PhantomData<fn(I)>);
+impl<I: for<'a> DistributedIteratorMulti<&'a ()>> DistributedIterator for Connect<I> where {}
+
+struct Cloned<Source>(PhantomData<fn(Source)>);
+impl<'a, Source> DistributedIteratorMulti<&'a Source> for Cloned<&'a Source> {
+    type Item = ();
+}
+
+struct Map<I, F> {
+    i: I,
+    f: F,
+}
+impl<I: DistributedIteratorMulti<Source>, F, Source> DistributedIteratorMulti<Source> for Map<I, F>
+where
+    F: A<<I as DistributedIteratorMulti<Source>>::Item>,
+{
+    type Item = ();
+}
+
+trait A<B> {}
+
+struct X;
+impl A<()> for X {}
+
+fn multi<I>(_reducer: I)
+where
+    I: for<'a> DistributedIteratorMulti<&'a ()>,
+{
+    DistributedIterator::reduce(Connect::<I>(PhantomData))
+}
+
+fn main() {
+    multi(Map { //~ ERROR implementation of `DistributedIteratorMulti` is not general enough
+        i: Cloned(PhantomData),
+        f: X,
+    });
+}