1 files changed, 20 insertions, 0 deletions
diff --git a/src/test/ui/coherence/coherence-impl-trait-for-trait.rs b/src/test/ui/coherence/coherence-impl-trait-for-trait.rs
new file mode 100644
index 000000000..195a37f15
--- /dev/null
+++ b/src/test/ui/coherence/coherence-impl-trait-for-trait.rs
@@ -0,0 +1,20 @@
+// Test that we give suitable error messages when the user attempts to
+// impl a trait `Trait` for its own object type.
+
+trait Foo { fn dummy(&self) { } }
+trait Bar: Foo { }
+trait Baz: Bar { }
+
+// Supertraits of Baz are not legal:
+impl Foo for dyn Baz { }
+//~^ ERROR E0371
+impl Bar for dyn Baz { }
+//~^ ERROR E0371
+impl Baz for dyn Baz { }
+//~^ ERROR E0371
+
+// But other random traits are:
+trait Other { }
+impl Other for dyn Baz { } // OK, Other not a supertrait of Baz
+
+fn main() { }