1 files changed, 33 insertions, 0 deletions
diff --git a/src/test/ui/impl-trait/nested-return-type2-tait.rs b/src/test/ui/impl-trait/nested-return-type2-tait.rs
new file mode 100644
index 000000000..42613d5cc
--- /dev/null
+++ b/src/test/ui/impl-trait/nested-return-type2-tait.rs
@@ -0,0 +1,33 @@
+#![feature(type_alias_impl_trait)]
+
+// check-pass
+
+trait Duh {}
+
+impl Duh for i32 {}
+
+trait Trait {
+    type Assoc: Duh;
+}
+
+// the fact that `R` is the `::Output` projection on `F` causes
+// an intermediate inference var to be generated which is then later
+// compared against the actually found `Assoc` type.
+impl<R: Duh, F: FnMut() -> R> Trait for F {
+    type Assoc = R;
+}
+
+type Sendable = impl Send;
+
+// The `Sendable` here is converted to an inference var and then later compared
+// against the inference var created, causing the inference var to be set to
+// the hidden type of `Sendable` instead of
+// the hidden type. We already have obligations registered on the inference
+// var to make it uphold the `: Duh` bound on `Trait::Assoc`. The opaque
+// type does not implement `Duh`, but if its hidden type does.
+fn foo() -> impl Trait<Assoc = Sendable> {
+    || 42
+}
+
+fn main() {
+}