1 files changed, 7 insertions, 0 deletions
diff --git a/tests/ui/typeck/issue-57404.rs b/tests/ui/typeck/issue-57404.rs
new file mode 100644
index 000000000..ecabca66a
--- /dev/null
+++ b/tests/ui/typeck/issue-57404.rs
@@ -0,0 +1,7 @@
+#![feature(unboxed_closures)]
+#![feature(fn_traits)]
+
+fn main() {
+    let handlers: Option<Box<dyn for<'a> FnMut<&'a mut (), Output=()>>> = None;
+    handlers.unwrap().as_mut().call_mut(&mut ()); //~ ERROR: `&mut ()` is not a tuple
+}