1 files changed, 65 insertions, 0 deletions
diff --git a/src/test/ui/traits/issue-43132.rs b/src/test/ui/traits/issue-43132.rs
new file mode 100644
index 000000000..c886f4b0a
--- /dev/null
+++ b/src/test/ui/traits/issue-43132.rs
@@ -0,0 +1,65 @@
+// run-pass
+#![allow(unused)]
+
+fn main() {
+}
+
+fn foo() {
+    let b = mk::<
+        Forward<(Box<dyn Future<Error = u32>>,)>,
+    >();
+    b.map_err(|_| ()).join();
+}
+
+fn mk<T>() -> T {
+    loop {}
+}
+
+impl<I: Future<Error = E>, E> Future for (I,) {
+    type Error = E;
+}
+
+struct Forward<T: Future> {
+    _a: T,
+}
+
+impl<T: Future> Future for Forward<T>
+where
+    T::Error: From<u32>,
+{
+    type Error = T::Error;
+}
+
+trait Future {
+    type Error;
+
+    fn map_err<F, E>(self, _: F) -> (Self, F)
+    where
+        F: FnOnce(Self::Error) -> E,
+        Self: Sized,
+    {
+        loop {}
+    }
+
+    fn join(self) -> (MaybeDone<Self>, ())
+    where
+        Self: Sized,
+    {
+        loop {}
+    }
+}
+
+impl<S: ?Sized + Future> Future for Box<S> {
+    type Error = S::Error;
+}
+
+enum MaybeDone<A: Future> {
+    _Done(A::Error),
+}
+
+impl<U, A: Future, F> Future for (A, F)
+where
+    F: FnOnce(A::Error) -> U,
+{
+    type Error = U;
+}