macros: fix the hygiene issue of join! and try_join! (#7766)

Signed-off-by: ADD-SP <[email protected]>

tests-build/tests/fail/macros_try_join.rs

@@ -0,0 +1,42 @@
+use tests_build::tokio;
+
+#[tokio::main]
+async fn main() {
+    // do not leak `RotatorSelect`
+    let _ = tokio::try_join!(async {
+        fn foo(_: impl RotatorSelect) {}
+    });
+
+    // do not leak `std::task::Poll::Pending`
+    let _ = tokio::try_join!(async { Pending });
+
+    // do not leak `std::task::Poll::Ready`
+    let _ = tokio::try_join!(async { Ready(0) });
+
+    // do not leak `std::future::Future`
+    let _ = tokio::try_join!(async {
+        struct MyFuture;
+
+        impl Future for MyFuture {
+            type Output = ();
+
+            fn poll(
+                self: std::pin::Pin<&mut Self>,
+                _cx: &mut std::task::Context<'_>,
+            ) -> std::task::Poll<Self::Output> {
+                todo!()
+            }
+        }
+    });
+
+    // do not leak `std::pin::Pin`
+    let _ = tokio::try_join!(async {
+        let mut x = 5;
+        let _ = Pin::new(&mut x);
+    });
+
+    // do not leak `std::future::poll_fn`
+    let _ = tokio::try_join!(async {
+        let _ = poll_fn(|_cx| todo!());
+    });
+}