1 files changed, 22 insertions, 0 deletions
diff --git a/tests/ui/traits/alias/only-maybe-bound.rs b/tests/ui/traits/alias/only-maybe-bound.rs
new file mode 100644
index 000000000..e4abf314e
--- /dev/null
+++ b/tests/ui/traits/alias/only-maybe-bound.rs
@@ -0,0 +1,22 @@
+// Test that `dyn ?Sized` (i.e., a trait object with only a maybe buond) is not allowed, when just
+// `?Sized` results from trait alias expansion.
+
+#![feature(trait_alias)]
+
+trait S = ?Sized;
+
+// Nest a couple of levels deep:
+trait _0 = S;
+trait _1 = _0;
+
+// Straight list expansion:
+type _T0 = dyn _1;
+//~^ ERROR at least one trait is required for an object type [E0224]
+
+// Twice:
+trait _2 = _1 + _1;
+
+type _T1 = dyn _2;
+//~^ ERROR at least one trait is required for an object type [E0224]
+
+fn main() {}