1 files changed, 29 insertions, 0 deletions

diff --git a/tests/ui/issues/issue-70746.rs b/tests/ui/issues/issue-70746.rs
new file mode 100644
index 000000000..8930c15f5
--- /dev/null
+++ b/tests/ui/issues/issue-70746.rs
@@ -0,0 +1,29 @@
+// check-pass
+
+pub trait Trait1 {
+    type C;
+}
+
+struct T1;
+impl Trait1 for T1 {
+    type C = usize;
+}
+pub trait Callback<T: Trait1>: FnMut(<T as Trait1>::C) {}
+impl<T: Trait1, F: FnMut(<T as Trait1>::C)> Callback<T> for F {}
+
+pub struct State<T: Trait1> {
+    callback: Option<Box<dyn Callback<T>>>,
+}
+impl<T: Trait1> State<T> {
+    fn new() -> Self {
+        Self { callback: None }
+    }
+    fn test_cb(&mut self, d: <T as Trait1>::C) {
+        (self.callback.as_mut().unwrap())(d)
+    }
+}
+
+fn main() {
+    let mut s = State::<T1>::new();
+    s.test_cb(1);
+}