In ConstructCoroutineInClosureShim, pass receiver by ref, not pointer

compiler/rustc_mir_transform/src/shim.rs

@@ -1015,8 +1015,8 @@ fn build_construct_coroutine_by_move_shim<'tcx>(
         bug!();
     };
 
-    // We use `*mut Self` here because we only need to emit an ABI-compatible shim body,
-    // rather than match the signature exactly.
+    // We use `&mut Self` here because we only need to emit an ABI-compatible shim body,
+    // rather than match the signature exactly (which might take `&self` instead).
     //
     // The self type here is a coroutine-closure, not a coroutine, and we never read from
     // it because it never has any captures, because this is only true in the Fn/FnMut
@@ -1025,7 +1025,7 @@ fn build_construct_coroutine_by_move_shim<'tcx>(
     if receiver_by_ref {
         // Triple-check that there's no captures here.
         assert_eq!(args.as_coroutine_closure().tupled_upvars_ty(), tcx.types.unit);
-        self_ty = Ty::new_mut_ptr(tcx, self_ty);
+        self_ty = Ty::new_mut_ref(tcx, tcx.lifetimes.re_erased, self_ty);
     }
 
     let poly_sig = args.as_coroutine_closure().coroutine_closure_sig().map_bound(|sig| {

compiler/rustc_ty_utils/src/abi.rs

@@ -125,8 +125,12 @@ fn fn_sig_for_fn_abi<'tcx>(
                     coroutine_kind = ty::ClosureKind::FnOnce;
 
                     // Implementations of `FnMut` and `Fn` for coroutine-closures
-                    // still take their receiver by ref.
-                    if receiver_by_ref { Ty::new_mut_ptr(tcx, coroutine_ty) } else { coroutine_ty }
+                    // still take their receiver by (mut) ref.
+                    if receiver_by_ref {
+                        Ty::new_mut_ref(tcx, tcx.lifetimes.re_erased, coroutine_ty)
+                    } else {
+                        coroutine_ty
+                    }
                 } else {
                     tcx.closure_env_ty(coroutine_ty, coroutine_kind, env_region)
                 };

src/tools/miri/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;
+    });
+}

src/tools/miri/tests/pass/async-closure-drop.stdout

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

src/tools/miri/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;
     });
-}
+}

src/tools/miri/tests/pass/async-closure.stdout

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