1 files changed, 28 insertions, 0 deletions
diff --git a/src/test/ui/type-alias-impl-trait/generic_duplicate_param_use.rs b/src/test/ui/type-alias-impl-trait/generic_duplicate_param_use.rs
new file mode 100644
index 000000000..093c1c231
--- /dev/null
+++ b/src/test/ui/type-alias-impl-trait/generic_duplicate_param_use.rs
@@ -0,0 +1,28 @@
+#![feature(type_alias_impl_trait)]
+
+use std::fmt::Debug;
+
+fn main() {}
+
+// test that unused generic parameters are ok
+type TwoTys<T, U> = impl Debug;
+
+type TwoLifetimes<'a, 'b> = impl Debug;
+
+type TwoConsts<const X: usize, const Y: usize> = impl Debug;
+
+
+fn one_ty<T: Debug>(t: T) -> TwoTys<T, T> {
+    t
+    //~^ ERROR non-defining opaque type use in defining scope
+}
+
+fn one_lifetime<'a>(t: &'a u32) -> TwoLifetimes<'a, 'a> {
+    t
+    //~^ ERROR non-defining opaque type use in defining scope
+}
+
+fn one_const<const N: usize>(t: *mut [u8; N]) -> TwoConsts<N, N> {
+    t
+    //~^ ERROR non-defining opaque type use in defining scope
+}