add test for trait-system-refactor-initiative/239

Author: jdonszelmann

tests/ui/coroutine/handle_opaques_before_coroutines.rs

@@ -0,0 +1,15 @@
+// test for https://github.com/rust-lang/trait-system-refactor-initiative/issues/239
+//@edition: 2024
+//@ check-pass
+//@ revisions: current next
+//@ ignore-compare-mode-next-solver (explicit revisions)
+//@[next] compile-flags: -Znext-solver
+
+fn foo<'a>() -> impl Send {
+    if false {
+        foo();
+    }
+    async {}
+}
+
+fn main() {}