1 files changed, 22 insertions, 0 deletions
diff --git a/src/test/ui/lint/must_use-trait.rs b/src/test/ui/lint/must_use-trait.rs
new file mode 100644
index 00000000000..23df4fa6132
--- /dev/null
+++ b/src/test/ui/lint/must_use-trait.rs
@@ -0,0 +1,22 @@
+#![deny(unused_must_use)]
+
+#[must_use]
+trait Critical {}
+
+trait NotSoCritical {}
+
+trait DecidedlyUnimportant {}
+
+struct Anon;
+
+impl Critical for Anon {}
+impl NotSoCritical for Anon {}
+impl DecidedlyUnimportant for Anon {}
+
+fn get_critical() -> impl NotSoCritical + Critical + DecidedlyUnimportant {
+    Anon {}
+}
+
+fn main() {
+    get_critical(); //~ ERROR unused implementer of `Critical` that must be used
+}