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src/test/ui/issues/issue-65419/issue-65419-async-fn-resume-after-completion.rs

@@ -0,0 +1,44 @@
+// issue 65419 - Attempting to run an async fn after completion mentions generators when it should
+// be talking about `async fn`s instead.
+
+// run-fail
+// error-pattern: thread 'main' panicked at '`async fn` resumed after completion'
+// compile-flags: --edition 2018
+
+#![feature(generators, generator_trait)]
+
+async fn foo() {
+}
+
+fn main() {
+    let mut future = Box::pin(foo());
+    executor::block_on(future.as_mut());
+    executor::block_on(future.as_mut());
+}
+
+mod executor {
+    use core::{
+        future::Future,
+        pin::Pin,
+        task::{Context, Poll, RawWaker, RawWakerVTable, Waker},
+    };
+
+    pub fn block_on<F: Future>(mut future: F) -> F::Output {
+        let mut future = unsafe { Pin::new_unchecked(&mut future) };
+
+        static VTABLE: RawWakerVTable = RawWakerVTable::new(
+            |_| unimplemented!("clone"),
+            |_| unimplemented!("wake"),
+            |_| unimplemented!("wake_by_ref"),
+            |_| (),
+        );
+        let waker = unsafe { Waker::from_raw(RawWaker::new(core::ptr::null(), &VTABLE)) };
+        let mut context = Context::from_waker(&waker);
+
+        loop {
+            if let Poll::Ready(val) = future.as_mut().poll(&mut context) {
+                break val;
+            }
+        }
+    }
+}

src/test/ui/issues/issue-65419/issue-65419-async-fn-resume-after-panic.rs

@@ -0,0 +1,50 @@
+// issue 65419 - Attempting to run an async fn after completion mentions generators when it should
+// be talking about `async fn`s instead. Should also test what happens when it panics.
+
+// run-fail
+// error-pattern: thread 'main' panicked at '`async fn` resumed after panic'
+// compile-flags: --edition 2018
+
+#![feature(generators, generator_trait)]
+
+use std::panic;
+
+async fn foo() {
+    panic!();
+}
+
+fn main() {
+    let mut future = Box::pin(foo());
+    panic::catch_unwind(panic::AssertUnwindSafe(|| {
+        executor::block_on(future.as_mut());
+    }));
+
+    executor::block_on(future.as_mut());
+}
+
+mod executor {
+    use core::{
+        future::Future,
+        pin::Pin,
+        task::{Context, Poll, RawWaker, RawWakerVTable, Waker},
+    };
+
+    pub fn block_on<F: Future>(mut future: F) -> F::Output {
+        let mut future = unsafe { Pin::new_unchecked(&mut future) };
+
+        static VTABLE: RawWakerVTable = RawWakerVTable::new(
+            |_| unimplemented!("clone"),
+            |_| unimplemented!("wake"),
+            |_| unimplemented!("wake_by_ref"),
+            |_| (),
+        );
+        let waker = unsafe { Waker::from_raw(RawWaker::new(core::ptr::null(), &VTABLE)) };
+        let mut context = Context::from_waker(&waker);
+
+        loop {
+            if let Poll::Ready(val) = future.as_mut().poll(&mut context) {
+                break val;
+            }
+        }
+    }
+}

src/test/ui/issues/issue-65419/issue-65419-generator-resume-after-completion.rs

@@ -0,0 +1,22 @@
+// issue 65419 - Attempting to run an `async fn` after completion mentions generators when it should
+// be talking about `async fn`s instead. Regression test added to make sure generators still
+// panic when resumed after completion.
+
+// run-fail
+// error-pattern:generator resumed after completion
+
+#![feature(generators, generator_trait)]
+
+use std::{
+    ops::Generator,
+    pin::Pin,
+};
+
+fn main() {
+    let mut g = || {
+        yield;
+    };
+    Pin::new(&mut g).resume(); // Yields once.
+    Pin::new(&mut g).resume(); // Completes here.
+    Pin::new(&mut g).resume(); // Panics here.
+}