1 files changed, 25 insertions, 0 deletions
diff --git a/src/test/ui/type-alias-impl-trait/reveal_local.rs b/src/test/ui/type-alias-impl-trait/reveal_local.rs
new file mode 100644
index 000000000..7ecb55353
--- /dev/null
+++ b/src/test/ui/type-alias-impl-trait/reveal_local.rs
@@ -0,0 +1,25 @@
+#![feature(type_alias_impl_trait)]
+
+use std::fmt::Debug;
+
+type Foo = impl Debug;
+//~^ ERROR cycle detected
+
+fn is_send<T: Send>() { }
+
+fn not_good() {
+    // Error: this function does not constrain `Foo` to any particular
+    // hidden type, so it cannot rely on `Send` being true.
+    is_send::<Foo>();
+}
+
+fn not_gooder() {
+    // Constrain `Foo = u32`
+    let x: Foo = 22_u32;
+
+    // while we could know this from the hidden type, it would
+    // need extra roundabout logic to support it.
+    is_send::<Foo>();
+}
+
+fn main() {}