test drop order for locals when a future is dropped part-way through …

…execution

src/test/ui/async-await/drop-order/drop-order-for-locals-when-cancelled.rs

@@ -0,0 +1,176 @@
+// aux-build:arc_wake.rs
+// edition:2018
+// run-pass
+
+#![allow(unused_variables)]
+#![deny(dead_code)]
+#![feature(async_await)]
+
+// Test that the drop order for locals in a fn and async fn matches up.
+extern crate arc_wake;
+
+use arc_wake::ArcWake;
+use std::cell::RefCell;
+use std::future::Future;
+use std::marker::PhantomData;
+use std::pin::Pin;
+use std::rc::Rc;
+use std::sync::Arc;
+use std::task::{Context, Poll};
+
+struct EmptyWaker;
+
+impl ArcWake for EmptyWaker {
+    fn wake(self: Arc<Self>) {}
+}
+
+#[derive(Debug, Eq, PartialEq)]
+enum DropOrder {
+    Function,
+    Val(&'static str),
+}
+
+type DropOrderListPtr = Rc<RefCell<Vec<DropOrder>>>;
+
+struct D(&'static str, DropOrderListPtr);
+
+impl Drop for D {
+    fn drop(&mut self) {
+        self.1.borrow_mut().push(DropOrder::Val(self.0));
+    }
+}
+
+struct NeverReady;
+
+impl Future for NeverReady {
+    type Output = ();
+    fn poll(mut self: Pin<&mut Self>, cx: &mut Context) -> Poll<Self::Output> {
+        Poll::Pending
+    }
+}
+
+async fn simple_variable_declaration_async(l: DropOrderListPtr) {
+    l.borrow_mut().push(DropOrder::Function);
+    let x = D("x", l.clone());
+    let y = D("y", l.clone());
+    NeverReady.await;
+}
+
+fn simple_variable_declaration_sync(l: DropOrderListPtr) {
+    l.borrow_mut().push(DropOrder::Function);
+    let x = D("x", l.clone());
+    let y = D("y", l.clone());
+}
+
+async fn varable_completely_contained_within_block_async(l: DropOrderListPtr) {
+    l.borrow_mut().push(DropOrder::Function);
+    async {
+        let x = D("x", l.clone());
+    }
+        .await;
+    let y = D("y", l.clone());
+    NeverReady.await;
+}
+
+fn varable_completely_contained_within_block_sync(l: DropOrderListPtr) {
+    l.borrow_mut().push(DropOrder::Function);
+    {
+        let x = D("x", l.clone());
+    }
+    let y = D("y", l.clone());
+}
+
+async fn variables_moved_into_separate_blocks_async(l: DropOrderListPtr) {
+    l.borrow_mut().push(DropOrder::Function);
+    let x = D("x", l.clone());
+    let y = D("y", l.clone());
+    async move { x }.await;
+    async move { y }.await;
+    NeverReady.await;
+}
+
+fn variables_moved_into_separate_blocks_sync(l: DropOrderListPtr) {
+    l.borrow_mut().push(DropOrder::Function);
+    let x = D("x", l.clone());
+    let y = D("y", l.clone());
+    {
+        x
+    };
+    {
+        y
+    };
+}
+
+async fn variables_moved_into_same_block_async(l: DropOrderListPtr) {
+    l.borrow_mut().push(DropOrder::Function);
+    let x = D("x", l.clone());
+    let y = D("y", l.clone());
+    async move {
+        x;
+        y;
+    };
+    NeverReady.await;
+}
+
+fn variables_moved_into_same_block_sync(l: DropOrderListPtr) {
+    l.borrow_mut().push(DropOrder::Function);
+    let x = D("x", l.clone());
+    let y = D("y", l.clone());
+    {
+        x;
+        y;
+    };
+    return;
+}
+
+async fn move_after_current_await_doesnt_affect_order(l: DropOrderListPtr) {
+    l.borrow_mut().push(DropOrder::Function);
+    let x = D("x", l.clone());
+    let y = D("y", l.clone());
+    NeverReady.await;
+    async move {
+        x;
+        y;
+    };
+}
+
+fn assert_drop_order_after_cancel<Fut: Future<Output = ()>>(
+    f: impl FnOnce(DropOrderListPtr) -> Fut,
+    g: impl FnOnce(DropOrderListPtr),
+) {
+    let empty = Arc::new(EmptyWaker);
+    let waker = ArcWake::into_waker(empty);
+    let mut cx = Context::from_waker(&waker);
+
+    let actual_order = Rc::new(RefCell::new(Vec::new()));
+    let mut fut = Box::pin(f(actual_order.clone()));
+    let _ = fut.as_mut().poll(&mut cx);
+    drop(fut);
+
+    let expected_order = Rc::new(RefCell::new(Vec::new()));
+    g(expected_order.clone());
+    assert_eq!(*actual_order.borrow(), *expected_order.borrow());
+}
+
+fn main() {
+    assert_drop_order_after_cancel(
+        simple_variable_declaration_async,
+        simple_variable_declaration_sync,
+    );
+    assert_drop_order_after_cancel(
+        varable_completely_contained_within_block_async,
+        varable_completely_contained_within_block_sync,
+    );
+    assert_drop_order_after_cancel(
+        variables_moved_into_separate_blocks_async,
+        variables_moved_into_separate_blocks_sync,
+    );
+    assert_drop_order_after_cancel(
+        variables_moved_into_same_block_async,
+        variables_moved_into_same_block_sync,
+    );
+    assert_drop_order_after_cancel(
+        move_after_current_await_doesnt_affect_order,
+        simple_variable_declaration_sync,
+    );
+}