1 files changed, 13 insertions, 0 deletions
diff --git a/src/test/ui/closures/closure-immutable-outer-variable.rs b/src/test/ui/closures/closure-immutable-outer-variable.rs
new file mode 100644
index 000000000..50ec1c614
--- /dev/null
+++ b/src/test/ui/closures/closure-immutable-outer-variable.rs
@@ -0,0 +1,13 @@
+// run-rustfix
+
+// Point at the captured immutable outer variable
+
+fn foo(mut f: Box<dyn FnMut()>) {
+    f();
+}
+
+fn main() {
+    let y = true;
+    foo(Box::new(move || y = !y) as Box<_>);
+    //~^ ERROR cannot assign to `y`, as it is not declared as mutable
+}