Rollup merge of #123049 - compiler-errors:coroutine-closure-rcvr, r=oli-obk

In `ConstructCoroutineInClosureShim`, pass receiver by mut ref, not mut pointer

The receivers were compatible at codegen time, but did not necessarily have the same layouts due to niches, which was caught by miri.

Fixes #3400

r? oli-obk

Author: matthiaskrgr

tests/pass/async-closure-drop.rs

@@ -0,0 +1,40 @@
+#![feature(async_closure, noop_waker, async_fn_traits)]
+
+use std::future::Future;
+use std::pin::pin;
+use std::task::*;
+
+pub fn block_on<T>(fut: impl Future<Output = T>) -> T {
+    let mut fut = pin!(fut);
+    let ctx = &mut Context::from_waker(Waker::noop());
+
+    loop {
+        match fut.as_mut().poll(ctx) {
+            Poll::Pending => {}
+            Poll::Ready(t) => break t,
+        }
+    }
+}
+
+async fn call_once(f: impl async FnOnce(DropMe)) {
+    f(DropMe("world")).await;
+}
+
+#[derive(Debug)]
+struct DropMe(&'static str);
+
+impl Drop for DropMe {
+    fn drop(&mut self) {
+        println!("{}", self.0);
+    }
+}
+
+pub fn main() {
+    block_on(async {
+        let b = DropMe("hello");
+        let async_closure = async move |a: DropMe| {
+            println!("{a:?} {b:?}");
+        };
+        call_once(async_closure).await;
+    });
+}

tests/pass/async-closure-drop.stdout

@@ -0,0 +1,3 @@
+DropMe("world") DropMe("hello")
+world
+hello

tests/pass/async-closure.rs

@@ -1,6 +1,7 @@
 #![feature(async_closure, noop_waker, async_fn_traits)]
 
 use std::future::Future;
+use std::ops::{AsyncFnMut, AsyncFnOnce};
 use std::pin::pin;
 use std::task::*;
 
@@ -16,25 +17,36 @@ pub fn block_on<T>(fut: impl Future<Output = T>) -> T {
     }
 }
 
-async fn call_once(f: impl async FnOnce(DropMe)) {
-    f(DropMe("world")).await;
+async fn call_mut(f: &mut impl AsyncFnMut(i32)) {
+    f(0).await;
 }
 
-#[derive(Debug)]
-struct DropMe(&'static str);
+async fn call_once(f: impl AsyncFnOnce(i32)) {
+    f(1).await;
+}
 
-impl Drop for DropMe {
-    fn drop(&mut self) {
-        println!("{}", self.0);
-    }
+async fn call_normal<F: Future<Output = ()>>(f: &impl Fn(i32) -> F) {
+    f(0).await;
+}
+
+async fn call_normal_once<F: Future<Output = ()>>(f: impl FnOnce(i32) -> F) {
+    f(1).await;
 }
 
 pub fn main() {
     block_on(async {
-        let b = DropMe("hello");
-        let async_closure = async move |a: DropMe| {
-            println!("{a:?} {b:?}");
+        let b = 2i32;
+        let mut async_closure = async move |a: i32| {
+            println!("{a} {b}");
         };
+        call_mut(&mut async_closure).await;
         call_once(async_closure).await;
+
+        // No-capture closures implement `Fn`.
+        let async_closure = async move |a: i32| {
+            println!("{a}");
+        };
+        call_normal(&async_closure).await;
+        call_normal_once(async_closure).await;
     });
 }

tests/pass/async-closure.stdout

@@ -1,3 +1,4 @@
-DropMe("world") DropMe("hello")
-world
-hello
+0 2
+1 2
+0
+1