add test for #2068

Author: RalfJung

tests/run-pass/issue-miri-2068.rs

@@ -0,0 +1,48 @@
+#![feature(pin_macro)]
+
+use core::future::Future;
+use core::pin::Pin;
+use core::task::{Context, Poll};
+
+use std::sync::Arc;
+
+struct NopWaker;
+
+impl std::task::Wake for NopWaker {
+    fn wake(self: Arc<Self>) {}
+}
+
+pub fn fuzzing_block_on<O, F: Future<Output = O>>(fut: F) -> O {
+    let mut fut = std::pin::pin!(fut);
+    let waker = std::task::Waker::from(Arc::new(NopWaker));
+    let mut context = std::task::Context::from_waker(&waker);
+    loop {
+        match fut.as_mut().poll(&mut context) {
+            Poll::Ready(v) => return v,
+            Poll::Pending => {}
+        }
+    }
+}
+
+pub struct LastFuture<S> {
+    last: S,
+}
+
+impl<S> Future for LastFuture<S>
+where
+    Self: Unpin,
+    S: Unpin + Copy,
+{
+    type Output = S;
+
+    fn poll(self: Pin<&mut Self>, _cx: &mut Context<'_>) -> Poll<Self::Output> {
+        return Poll::Ready(self.last);
+    }
+}
+
+fn main() {
+    fuzzing_block_on(async {
+        LastFuture { last: &0u32 }.await;
+        LastFuture { last: Option::<u32>::None }.await;
+    });
+}