44 files changed, 267 insertions, 6 deletions

diff --git a/src/test/ui/async-await/in-trait/async-associated-types.rs b/tests/ui/async-await/in-trait/async-associated-types.rs
index 974f5aaff..974f5aaff 100644
--- a/src/test/ui/async-await/in-trait/async-associated-types.rs
+++ b/tests/ui/async-await/in-trait/async-associated-types.rs
diff --git a/src/test/ui/async-await/in-trait/async-associated-types2.rs b/tests/ui/async-await/in-trait/async-associated-types2.rs
index e546a0579..e546a0579 100644
--- a/src/test/ui/async-await/in-trait/async-associated-types2.rs
+++ b/tests/ui/async-await/in-trait/async-associated-types2.rs
diff --git a/src/test/ui/async-await/in-trait/async-example-desugared-boxed-in-trait.rs b/tests/ui/async-await/in-trait/async-example-desugared-boxed-in-trait.rs
index 38ba29718..38ba29718 100644
--- a/src/test/ui/async-await/in-trait/async-example-desugared-boxed-in-trait.rs
+++ b/tests/ui/async-await/in-trait/async-example-desugared-boxed-in-trait.rs
diff --git a/src/test/ui/async-await/in-trait/async-example-desugared-boxed-in-trait.stderr b/tests/ui/async-await/in-trait/async-example-desugared-boxed-in-trait.stderr
index 22d2928f2..13e722255 100644
--- a/src/test/ui/async-await/in-trait/async-example-desugared-boxed-in-trait.stderr
+++ b/tests/ui/async-await/in-trait/async-example-desugared-boxed-in-trait.stderr
@@ -9,8 +9,8 @@ note: type in trait
    |
 LL |     fn foo(&self) -> Pin<Box<dyn Future<Output = i32> + '_>>;
    |                      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-   = note: expected fn pointer `fn(&i32) -> Pin<Box<dyn Future<Output = i32>>>`
-              found fn pointer `fn(&i32) -> impl Future<Output = i32>`
+   = note: expected signature `fn(&i32) -> Pin<Box<dyn Future<Output = i32>>>`
+              found signature `fn(&i32) -> impl Future<Output = i32>`
 
 error: aborting due to previous error
 
diff --git a/tests/ui/async-await/in-trait/async-example-desugared-boxed.rs b/tests/ui/async-await/in-trait/async-example-desugared-boxed.rs
new file mode 100644
index 000000000..1b1b3cffd
--- /dev/null
+++ b/tests/ui/async-await/in-trait/async-example-desugared-boxed.rs
@@ -0,0 +1,21 @@
+// edition: 2021
+
+#![feature(async_fn_in_trait)]
+#![feature(return_position_impl_trait_in_trait)]
+#![allow(incomplete_features)]
+
+use std::future::Future;
+use std::pin::Pin;
+
+trait MyTrait {
+    async fn foo(&self) -> i32;
+}
+
+impl MyTrait for i32 {
+    fn foo(&self) -> Pin<Box<dyn Future<Output = i32> + '_>> {
+        //~^ ERROR method `foo` should be async
+        Box::pin(async { *self })
+    }
+}
+
+fn main() {}
diff --git a/tests/ui/async-await/in-trait/async-example-desugared-boxed.stderr b/tests/ui/async-await/in-trait/async-example-desugared-boxed.stderr
new file mode 100644
index 000000000..60fa534a6
--- /dev/null
+++ b/tests/ui/async-await/in-trait/async-example-desugared-boxed.stderr
@@ -0,0 +1,11 @@
+error: method `foo` should be async because the method from the trait is async
+  --> $DIR/async-example-desugared-boxed.rs:15:5
+   |
+LL |     async fn foo(&self) -> i32;
+   |     --------------------------- required because the trait method is async
+...
+LL |     fn foo(&self) -> Pin<Box<dyn Future<Output = i32> + '_>> {
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to previous error
+
diff --git a/tests/ui/async-await/in-trait/async-example-desugared-extra.rs b/tests/ui/async-await/in-trait/async-example-desugared-extra.rs
new file mode 100644
index 000000000..81e1e59a3
--- /dev/null
+++ b/tests/ui/async-await/in-trait/async-example-desugared-extra.rs
@@ -0,0 +1,37 @@
+// check-pass
+// edition: 2021
+
+#![feature(async_fn_in_trait)]
+#![feature(return_position_impl_trait_in_trait)]
+#![allow(incomplete_features)]
+
+use std::future::Future;
+use std::pin::Pin;
+use std::task::Poll;
+
+trait MyTrait {
+    async fn foo(&self) -> i32;
+}
+
+#[derive(Clone)]
+struct MyFuture(i32);
+
+impl Future for MyFuture {
+    type Output = i32;
+    fn poll(
+        self: Pin<&mut Self>,
+        _: &mut std::task::Context<'_>,
+    ) -> Poll<<Self as Future>::Output> {
+        Poll::Ready(self.0)
+    }
+}
+
+impl MyTrait for i32 {
+    // FIXME: this should eventually require `#[refine]` to compile, because it also provides
+    // `Clone`.
+    fn foo(&self) -> impl Future<Output = i32> + Clone {
+        MyFuture(*self)
+    }
+}
+
+fn main() {}
diff --git a/src/test/ui/async-await/in-trait/async-example-desugared-in-trait.rs b/tests/ui/async-await/in-trait/async-example-desugared-in-trait.rs
index feeda719e..feeda719e 100644
--- a/src/test/ui/async-await/in-trait/async-example-desugared-in-trait.rs
+++ b/tests/ui/async-await/in-trait/async-example-desugared-in-trait.rs
diff --git a/tests/ui/async-await/in-trait/async-example-desugared-manual.rs b/tests/ui/async-await/in-trait/async-example-desugared-manual.rs
new file mode 100644
index 000000000..71473e745
--- /dev/null
+++ b/tests/ui/async-await/in-trait/async-example-desugared-manual.rs
@@ -0,0 +1,29 @@
+// edition: 2021
+
+#![feature(async_fn_in_trait)]
+#![feature(return_position_impl_trait_in_trait)]
+#![allow(incomplete_features)]
+
+use std::future::Future;
+use std::task::Poll;
+
+trait MyTrait {
+    async fn foo(&self) -> i32;
+}
+
+struct MyFuture;
+impl Future for MyFuture {
+    type Output = i32;
+    fn poll(self: std::pin::Pin<&mut Self>, _: &mut std::task::Context<'_>) -> Poll<Self::Output> {
+        Poll::Ready(0)
+    }
+}
+
+impl MyTrait for u32 {
+    fn foo(&self) -> MyFuture {
+        //~^ ERROR method `foo` should be async
+        MyFuture
+    }
+}
+
+fn main() {}
diff --git a/tests/ui/async-await/in-trait/async-example-desugared-manual.stderr b/tests/ui/async-await/in-trait/async-example-desugared-manual.stderr
new file mode 100644
index 000000000..567a36a86
--- /dev/null
+++ b/tests/ui/async-await/in-trait/async-example-desugared-manual.stderr
@@ -0,0 +1,11 @@
+error: method `foo` should be async because the method from the trait is async
+  --> $DIR/async-example-desugared-manual.rs:23:5
+   |
+LL |     async fn foo(&self) -> i32;
+   |     --------------------------- required because the trait method is async
+...
+LL |     fn foo(&self) -> MyFuture {
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to previous error
+
diff --git a/tests/ui/async-await/in-trait/async-example-desugared.rs b/tests/ui/async-await/in-trait/async-example-desugared.rs
new file mode 100644
index 000000000..fb92ec786
--- /dev/null
+++ b/tests/ui/async-await/in-trait/async-example-desugared.rs
@@ -0,0 +1,20 @@
+// check-pass
+// edition: 2021
+
+#![feature(async_fn_in_trait)]
+#![feature(return_position_impl_trait_in_trait)]
+#![allow(incomplete_features)]
+
+use std::future::Future;
+
+trait MyTrait {
+    async fn foo(&self) -> i32;
+}
+
+impl MyTrait for i32 {
+    fn foo(&self) -> impl Future<Output = i32> + '_ {
+        async { *self }
+    }
+}
+
+fn main() {}
diff --git a/src/test/ui/async-await/in-trait/async-example.rs b/tests/ui/async-await/in-trait/async-example.rs
index abf94ef74..abf94ef74 100644
--- a/src/test/ui/async-await/in-trait/async-example.rs
+++ b/tests/ui/async-await/in-trait/async-example.rs
diff --git a/src/test/ui/async-await/in-trait/async-generics-and-bounds.rs b/tests/ui/async-await/in-trait/async-generics-and-bounds.rs
index a73d55adf..a73d55adf 100644
--- a/src/test/ui/async-await/in-trait/async-generics-and-bounds.rs
+++ b/tests/ui/async-await/in-trait/async-generics-and-bounds.rs
diff --git a/src/test/ui/async-await/in-trait/async-generics-and-bounds.stderr b/tests/ui/async-await/in-trait/async-generics-and-bounds.stderr
index f1f0d7e59..f1f0d7e59 100644
--- a/src/test/ui/async-await/in-trait/async-generics-and-bounds.stderr
+++ b/tests/ui/async-await/in-trait/async-generics-and-bounds.stderr
diff --git a/src/test/ui/async-await/in-trait/async-generics.rs b/tests/ui/async-await/in-trait/async-generics.rs
index 67000e577..67000e577 100644
--- a/src/test/ui/async-await/in-trait/async-generics.rs
+++ b/tests/ui/async-await/in-trait/async-generics.rs
diff --git a/src/test/ui/async-await/in-trait/async-generics.stderr b/tests/ui/async-await/in-trait/async-generics.stderr
index 2f0556456..2f0556456 100644
--- a/src/test/ui/async-await/in-trait/async-generics.stderr
+++ b/tests/ui/async-await/in-trait/async-generics.stderr
diff --git a/src/test/ui/async-await/in-trait/async-lifetimes-and-bounds.rs b/tests/ui/async-await/in-trait/async-lifetimes-and-bounds.rs
index d5481d277..d5481d277 100644
--- a/src/test/ui/async-await/in-trait/async-lifetimes-and-bounds.rs
+++ b/tests/ui/async-await/in-trait/async-lifetimes-and-bounds.rs
diff --git a/src/test/ui/async-await/in-trait/async-lifetimes.rs b/tests/ui/async-await/in-trait/async-lifetimes.rs
index f298e45d2..f298e45d2 100644
--- a/src/test/ui/async-await/in-trait/async-lifetimes.rs
+++ b/tests/ui/async-await/in-trait/async-lifetimes.rs
diff --git a/src/test/ui/async-await/in-trait/async-recursive-generic.rs b/tests/ui/async-await/in-trait/async-recursive-generic.rs
index 6839abd38..6839abd38 100644
--- a/src/test/ui/async-await/in-trait/async-recursive-generic.rs
+++ b/tests/ui/async-await/in-trait/async-recursive-generic.rs
diff --git a/src/test/ui/async-await/in-trait/async-recursive-generic.stderr b/tests/ui/async-await/in-trait/async-recursive-generic.stderr
index cab173bdd..cab173bdd 100644
--- a/src/test/ui/async-await/in-trait/async-recursive-generic.stderr
+++ b/tests/ui/async-await/in-trait/async-recursive-generic.stderr
diff --git a/src/test/ui/async-await/in-trait/async-recursive.rs b/tests/ui/async-await/in-trait/async-recursive.rs
index 61119f809..61119f809 100644
--- a/src/test/ui/async-await/in-trait/async-recursive.rs
+++ b/tests/ui/async-await/in-trait/async-recursive.rs
diff --git a/src/test/ui/async-await/in-trait/async-recursive.stderr b/tests/ui/async-await/in-trait/async-recursive.stderr
index 9feff37b3..9feff37b3 100644
--- a/src/test/ui/async-await/in-trait/async-recursive.stderr
+++ b/tests/ui/async-await/in-trait/async-recursive.stderr
diff --git a/tests/ui/async-await/in-trait/bad-signatures.rs b/tests/ui/async-await/in-trait/bad-signatures.rs
new file mode 100644
index 000000000..b86f1d1c1
--- /dev/null
+++ b/tests/ui/async-await/in-trait/bad-signatures.rs
@@ -0,0 +1,16 @@
+// edition:2021
+
+#![feature(async_fn_in_trait)]
+//~^ WARN the feature `async_fn_in_trait` is incomplete
+
+trait MyTrait {
+    async fn bar(&abc self);
+    //~^ ERROR expected identifier, found keyword `self`
+    //~| ERROR expected one of `:`, `@`, or `|`, found keyword `self`
+}
+
+impl MyTrait for () {
+    async fn bar(&self) {}
+}
+
+fn main() {}
diff --git a/tests/ui/async-await/in-trait/bad-signatures.stderr b/tests/ui/async-await/in-trait/bad-signatures.stderr
new file mode 100644
index 000000000..e0ba7b53e
--- /dev/null
+++ b/tests/ui/async-await/in-trait/bad-signatures.stderr
@@ -0,0 +1,26 @@
+error: expected identifier, found keyword `self`
+  --> $DIR/bad-signatures.rs:7:23
+   |
+LL |     async fn bar(&abc self);
+   |                       ^^^^ expected identifier, found keyword
+
+error: expected one of `:`, `@`, or `|`, found keyword `self`
+  --> $DIR/bad-signatures.rs:7:23
+   |
+LL |     async fn bar(&abc self);
+   |                  -----^^^^
+   |                  |    |
+   |                  |    expected one of `:`, `@`, or `|`
+   |                  help: declare the type after the parameter binding: `<identifier>: <type>`
+
+warning: the feature `async_fn_in_trait` is incomplete and may not be safe to use and/or cause compiler crashes
+  --> $DIR/bad-signatures.rs:3:12
+   |
+LL | #![feature(async_fn_in_trait)]
+   |            ^^^^^^^^^^^^^^^^^
+   |
+   = note: see issue #91611 <https://github.com/rust-lang/rust/issues/91611> for more information
+   = note: `#[warn(incomplete_features)]` on by default
+
+error: aborting due to 2 previous errors; 1 warning emitted
+
diff --git a/src/test/ui/async-await/in-trait/early-bound-1.rs b/tests/ui/async-await/in-trait/early-bound-1.rs
index 6b3b14201..6b3b14201 100644
--- a/src/test/ui/async-await/in-trait/early-bound-1.rs
+++ b/tests/ui/async-await/in-trait/early-bound-1.rs
diff --git a/src/test/ui/async-await/in-trait/early-bound-2.rs b/tests/ui/async-await/in-trait/early-bound-2.rs
index 270443229..270443229 100644
--- a/src/test/ui/async-await/in-trait/early-bound-2.rs
+++ b/tests/ui/async-await/in-trait/early-bound-2.rs
diff --git a/src/test/ui/async-await/in-trait/fn-not-async-err.rs b/tests/ui/async-await/in-trait/fn-not-async-err.rs
index f94d32145..9598d53bc 100644
--- a/src/test/ui/async-await/in-trait/fn-not-async-err.rs
+++ b/tests/ui/async-await/in-trait/fn-not-async-err.rs
@@ -9,7 +9,7 @@ trait MyTrait {
 
 impl MyTrait for i32 {
     fn foo(&self) -> i32 {
-        //~^ ERROR: `i32` is not a future [E0277]
+        //~^ ERROR: method `foo` should be async
         *self
     }
 }
diff --git a/tests/ui/async-await/in-trait/fn-not-async-err.stderr b/tests/ui/async-await/in-trait/fn-not-async-err.stderr
new file mode 100644
index 000000000..579801d0f
--- /dev/null
+++ b/tests/ui/async-await/in-trait/fn-not-async-err.stderr
@@ -0,0 +1,11 @@
+error: method `foo` should be async because the method from the trait is async
+  --> $DIR/fn-not-async-err.rs:11:5
+   |
+LL |     async fn foo(&self) -> i32;
+   |     --------------------------- required because the trait method is async
+...
+LL |     fn foo(&self) -> i32 {
+   |     ^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to previous error
+
diff --git a/src/test/ui/async-await/in-trait/fn-not-async-err2.rs b/tests/ui/async-await/in-trait/fn-not-async-err2.rs
index 594baa91a..2c4ed5535 100644
--- a/src/test/ui/async-await/in-trait/fn-not-async-err2.rs
+++ b/tests/ui/async-await/in-trait/fn-not-async-err2.rs
@@ -12,9 +12,7 @@ trait MyTrait {
 impl MyTrait for i32 {
     fn foo(&self) -> impl Future<Output = i32> {
         //~^ ERROR `impl Trait` only allowed in function and inherent method return types, not in `impl` method return [E0562]
-        async {
-            *self
-        }
+        async { *self }
     }
 }
 
diff --git a/src/test/ui/async-await/in-trait/fn-not-async-err2.stderr b/tests/ui/async-await/in-trait/fn-not-async-err2.stderr
index f591f1847..f591f1847 100644
--- a/src/test/ui/async-await/in-trait/fn-not-async-err2.stderr
+++ b/tests/ui/async-await/in-trait/fn-not-async-err2.stderr
diff --git a/src/test/ui/async-await/in-trait/implied-bounds.rs b/tests/ui/async-await/in-trait/implied-bounds.rs
index 52bceb3cc..52bceb3cc 100644
--- a/src/test/ui/async-await/in-trait/implied-bounds.rs
+++ b/tests/ui/async-await/in-trait/implied-bounds.rs
diff --git a/src/test/ui/async-await/in-trait/issue-102138.rs b/tests/ui/async-await/in-trait/issue-102138.rs
index f61b34ed9..f61b34ed9 100644
--- a/src/test/ui/async-await/in-trait/issue-102138.rs
+++ b/tests/ui/async-await/in-trait/issue-102138.rs
diff --git a/src/test/ui/async-await/in-trait/issue-102219.rs b/tests/ui/async-await/in-trait/issue-102219.rs
index 9a35f6515..9a35f6515 100644
--- a/src/test/ui/async-await/in-trait/issue-102219.rs
+++ b/tests/ui/async-await/in-trait/issue-102219.rs
diff --git a/src/test/ui/async-await/in-trait/issue-102310.rs b/tests/ui/async-await/in-trait/issue-102310.rs
index 49c3e9fee..49c3e9fee 100644
--- a/src/test/ui/async-await/in-trait/issue-102310.rs
+++ b/tests/ui/async-await/in-trait/issue-102310.rs
diff --git a/tests/ui/async-await/in-trait/issue-104678.rs b/tests/ui/async-await/in-trait/issue-104678.rs
new file mode 100644
index 000000000..e396df4e5
--- /dev/null
+++ b/tests/ui/async-await/in-trait/issue-104678.rs
@@ -0,0 +1,31 @@
+// edition:2021
+// check-pass
+
+#![feature(async_fn_in_trait)]
+#![allow(incomplete_features)]
+
+use std::future::Future;
+pub trait Pool {
+    type Conn;
+
+    async fn async_callback<'a, F: FnOnce(&'a Self::Conn) -> Fut, Fut: Future<Output = ()>>(
+        &'a self,
+        callback: F,
+    ) -> ();
+}
+
+pub struct PoolImpl;
+pub struct ConnImpl;
+
+impl Pool for PoolImpl {
+    type Conn = ConnImpl;
+
+    async fn async_callback<'a, F: FnOnce(&'a Self::Conn) -> Fut, Fut: Future<Output = ()>>(
+        &'a self,
+        _callback: F,
+    ) -> () {
+        todo!()
+    }
+}
+
+fn main() {}
diff --git a/src/test/ui/async-await/in-trait/lifetime-mismatch.rs b/tests/ui/async-await/in-trait/lifetime-mismatch.rs
index 45ede193c..45ede193c 100644
--- a/src/test/ui/async-await/in-trait/lifetime-mismatch.rs
+++ b/tests/ui/async-await/in-trait/lifetime-mismatch.rs
diff --git a/src/test/ui/async-await/in-trait/lifetime-mismatch.stderr b/tests/ui/async-await/in-trait/lifetime-mismatch.stderr
index d87adcc78..d87adcc78 100644
--- a/src/test/ui/async-await/in-trait/lifetime-mismatch.stderr
+++ b/tests/ui/async-await/in-trait/lifetime-mismatch.stderr
diff --git a/tests/ui/async-await/in-trait/missing-send-bound.rs b/tests/ui/async-await/in-trait/missing-send-bound.rs
new file mode 100644
index 000000000..78922b59b
--- /dev/null
+++ b/tests/ui/async-await/in-trait/missing-send-bound.rs
@@ -0,0 +1,21 @@
+// edition:2021
+
+#![feature(async_fn_in_trait)]
+//~^ WARN the feature `async_fn_in_trait` is incomplete and may not be safe to use and/or cause compiler crashes
+
+trait Foo {
+    async fn bar();
+}
+
+async fn test<T: Foo>() {
+    T::bar().await;
+}
+
+fn test2<T: Foo>() {
+    assert_is_send(test::<T>());
+    //~^ ERROR future cannot be sent between threads safely
+}
+
+fn assert_is_send(_: impl Send) {}
+
+fn main() {}
diff --git a/tests/ui/async-await/in-trait/missing-send-bound.stderr b/tests/ui/async-await/in-trait/missing-send-bound.stderr
new file mode 100644
index 000000000..5cedf3ddb
--- /dev/null
+++ b/tests/ui/async-await/in-trait/missing-send-bound.stderr
@@ -0,0 +1,29 @@
+warning: the feature `async_fn_in_trait` is incomplete and may not be safe to use and/or cause compiler crashes
+  --> $DIR/missing-send-bound.rs:3:12
+   |
+LL | #![feature(async_fn_in_trait)]
+   |            ^^^^^^^^^^^^^^^^^
+   |
+   = note: see issue #91611 <https://github.com/rust-lang/rust/issues/91611> for more information
+   = note: `#[warn(incomplete_features)]` on by default
+
+error: future cannot be sent between threads safely
+  --> $DIR/missing-send-bound.rs:15:20
+   |
+LL |     assert_is_send(test::<T>());
+   |                    ^^^^^^^^^^^ future returned by `test` is not `Send`
+   |
+   = help: within `impl Future<Output = ()>`, the trait `Send` is not implemented for `impl Future<Output = ()>`
+note: future is not `Send` as it awaits another future which is not `Send`
+  --> $DIR/missing-send-bound.rs:11:5
+   |
+LL |     T::bar().await;
+   |     ^^^^^^^^ await occurs here on type `impl Future<Output = ()>`, which is not `Send`
+note: required by a bound in `assert_is_send`
+  --> $DIR/missing-send-bound.rs:19:27
+   |
+LL | fn assert_is_send(_: impl Send) {}
+   |                           ^^^^ required by this bound in `assert_is_send`
+
+error: aborting due to previous error; 1 warning emitted
+
diff --git a/src/test/ui/async-await/in-trait/nested-rpit.rs b/tests/ui/async-await/in-trait/nested-rpit.rs
index 41d72ebb4..41d72ebb4 100644
--- a/src/test/ui/async-await/in-trait/nested-rpit.rs
+++ b/tests/ui/async-await/in-trait/nested-rpit.rs
diff --git a/src/test/ui/async-await/in-trait/object-safety.rs b/tests/ui/async-await/in-trait/object-safety.rs
index a8bc35f7e..a8bc35f7e 100644
--- a/src/test/ui/async-await/in-trait/object-safety.rs
+++ b/tests/ui/async-await/in-trait/object-safety.rs
diff --git a/src/test/ui/async-await/in-trait/object-safety.stderr b/tests/ui/async-await/in-trait/object-safety.stderr
index 0b318f71f..0b318f71f 100644
--- a/src/test/ui/async-await/in-trait/object-safety.stderr
+++ b/tests/ui/async-await/in-trait/object-safety.stderr
diff --git a/src/test/ui/async-await/in-trait/return-type-suggestion.rs b/tests/ui/async-await/in-trait/return-type-suggestion.rs
index 3446761d1..3446761d1 100644
--- a/src/test/ui/async-await/in-trait/return-type-suggestion.rs
+++ b/tests/ui/async-await/in-trait/return-type-suggestion.rs
diff --git a/src/test/ui/async-await/in-trait/return-type-suggestion.stderr b/tests/ui/async-await/in-trait/return-type-suggestion.stderr
index 5a9b15e54..5a9b15e54 100644
--- a/src/test/ui/async-await/in-trait/return-type-suggestion.stderr
+++ b/tests/ui/async-await/in-trait/return-type-suggestion.stderr