1 files changed, 20 insertions, 0 deletions
diff --git a/src/test/ui/unboxed-closures/unboxed-closure-feature-gate.rs b/src/test/ui/unboxed-closures/unboxed-closure-feature-gate.rs
new file mode 100644
index 000000000..d8b201bf8
--- /dev/null
+++ b/src/test/ui/unboxed-closures/unboxed-closure-feature-gate.rs
@@ -0,0 +1,20 @@
+// Check that parenthetical notation is feature-gated except with the
+// `Fn` traits.
+
+use std::marker;
+
+trait Foo<A> {
+    type Output;
+
+    fn dummy(&self, a: A) { }
+}
+
+fn main() {
+    let x: Box<dyn Foo(isize)>;
+    //~^ ERROR parenthetical notation is only stable when used with `Fn`-family
+
+    // No errors with these:
+    let x: Box<dyn Fn(isize)>;
+    let x: Box<dyn FnMut(isize)>;
+    let x: Box<dyn FnOnce(isize)>;
+}