Add regression test for #64401

src/test/ui/codegen/issue-64401.rs

@@ -0,0 +1,51 @@
+// build-pass
+// The ICE didn't happen with `cargo check` but `cargo build`.
+
+use std::marker::PhantomData;
+
+trait Owned<'a> {
+    type Reader;
+}
+
+impl<'a> Owned<'a> for () {
+    type Reader = ();
+}
+
+trait Handler {
+    fn handle(&self);
+}
+
+struct CtxHandlerWithoutState<M, F> {
+    message_type: PhantomData<M>,
+    _function: F,
+}
+
+impl<M, F> CtxHandlerWithoutState<M, F> {
+    pub fn new(_function: F) -> Self {
+        Self {
+            message_type: PhantomData,
+            _function,
+        }
+    }
+}
+
+impl<'a, M, F> Handler for CtxHandlerWithoutState<M, F>
+where
+    F: Fn(<M as Owned<'a>>::Reader),
+    M: Owned<'a>,
+{
+    fn handle(&self) {}
+}
+
+fn e_to_i<M: for<'a> Owned<'a>>(_: <M as Owned<'_>>::Reader) {}
+
+fn send_external_to_internal<M>()
+where
+    M: for<'a> Owned<'a>,
+{
+    let _: Box<dyn Handler> = Box::new(CtxHandlerWithoutState::<M, _>::new(e_to_i::<M>));
+}
+
+fn main() {
+    send_external_to_internal::<()>()
+}