1 files changed, 18 insertions, 0 deletions
diff --git a/src/test/ui/type-alias-impl-trait/generic_duplicate_param_use3.rs b/src/test/ui/type-alias-impl-trait/generic_duplicate_param_use3.rs
new file mode 100644
index 000000000..e7a25fc72
--- /dev/null
+++ b/src/test/ui/type-alias-impl-trait/generic_duplicate_param_use3.rs
@@ -0,0 +1,18 @@
+#![feature(type_alias_impl_trait)]
+
+use std::fmt::Debug;
+
+fn main() {}
+
+// test that unused generic parameters are ok
+type Two<T, U> = impl Debug;
+
+fn two<T: Debug, U>(t: T, _: U) -> Two<T, U> {
+    t
+    //~^ ERROR `T` doesn't implement `Debug`
+}
+
+fn three<T, U: Debug>(_: T, u: U) -> Two<T, U> {
+    u
+    //~^ ERROR `U` doesn't implement `Debug`
+}