Add tests for static async functions in traits

This patch adds test cases for AFIT, the majority of which are currently
expected to run as `check-fail`.

src/test/ui/async-await/in-trait/async-associated-types.rs

@@ -0,0 +1,24 @@
+// edition: 2021
+
+#![feature(async_fn_in_trait)]
+#![allow(incomplete_features)]
+
+use std::fmt::Debug;
+
+trait MyTrait<'a, 'b, T> where Self: 'a, T: Debug + Sized + 'b {
+    type MyAssoc;// = (&'a T, &'b U);
+
+    async fn foo(&'a self, key: &'b T) -> Self::MyAssoc;
+}
+
+impl<'a, 'b, T: Debug + Sized + 'b, U: 'a> MyTrait<'a, 'b, T> for U {
+    type MyAssoc = (&'a U, &'b T);
+
+    async fn foo(&'a self, key: &'b T) -> (&'a U, &'b T) {
+        (self, key)
+    }
+}
+//~^^^^ ERROR cannot infer an appropriate lifetime for lifetime parameter `'a` due to conflicting requirements
+//~| ERROR cannot infer an appropriate lifetime for lifetime parameter `'b` due to conflicting requirements
+
+fn main() {}

src/test/ui/async-await/in-trait/async-associated-types.stderr

@@ -0,0 +1,57 @@
+error[E0495]: cannot infer an appropriate lifetime for lifetime parameter `'a` due to conflicting requirements
+  --> $DIR/async-associated-types.rs:17:43
+   |
+LL |     async fn foo(&'a self, key: &'b T) -> (&'a U, &'b T) {
+   |                                           ^^^^^^^^^^^^^^
+   |
+note: first, the lifetime cannot outlive the lifetime `'a` as defined here...
+  --> $DIR/async-associated-types.rs:14:6
+   |
+LL | impl<'a, 'b, T: Debug + Sized + 'b, U: 'a> MyTrait<'a, 'b, T> for U {
+   |      ^^
+note: ...so that the types are compatible
+  --> $DIR/async-associated-types.rs:17:43
+   |
+LL |     async fn foo(&'a self, key: &'b T) -> (&'a U, &'b T) {
+   |                                           ^^^^^^^^^^^^^^
+   = note: expected `(&'a U, &'b T)`
+              found `(&U, &T)`
+   = note: but, the lifetime must be valid for the static lifetime...
+note: ...so that the types are compatible
+  --> $DIR/async-associated-types.rs:17:43
+   |
+LL |     async fn foo(&'a self, key: &'b T) -> (&'a U, &'b T) {
+   |                                           ^^^^^^^^^^^^^^
+   = note: expected `MyTrait<'static, 'static, T>`
+              found `MyTrait<'_, '_, T>`
+
+error[E0495]: cannot infer an appropriate lifetime for lifetime parameter `'b` due to conflicting requirements
+  --> $DIR/async-associated-types.rs:17:43
+   |
+LL |     async fn foo(&'a self, key: &'b T) -> (&'a U, &'b T) {
+   |                                           ^^^^^^^^^^^^^^
+   |
+note: first, the lifetime cannot outlive the lifetime `'b` as defined here...
+  --> $DIR/async-associated-types.rs:14:10
+   |
+LL | impl<'a, 'b, T: Debug + Sized + 'b, U: 'a> MyTrait<'a, 'b, T> for U {
+   |          ^^
+note: ...so that the types are compatible
+  --> $DIR/async-associated-types.rs:17:43
+   |
+LL |     async fn foo(&'a self, key: &'b T) -> (&'a U, &'b T) {
+   |                                           ^^^^^^^^^^^^^^
+   = note: expected `(&'a U, &'b T)`
+              found `(&U, &T)`
+   = note: but, the lifetime must be valid for the static lifetime...
+note: ...so that the types are compatible
+  --> $DIR/async-associated-types.rs:17:43
+   |
+LL |     async fn foo(&'a self, key: &'b T) -> (&'a U, &'b T) {
+   |                                           ^^^^^^^^^^^^^^
+   = note: expected `MyTrait<'static, 'static, T>`
+              found `MyTrait<'_, '_, T>`
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0495`.

src/test/ui/async-await/in-trait/async-associated-types2-desugared.rs

@@ -0,0 +1,31 @@
+// edition: 2021
+
+#![feature(async_fn_in_trait)]
+#![allow(incomplete_features)]
+
+use std::future::Future;
+
+trait MyTrait {
+    type Fut<'a>: Future<Output = i32>
+    where
+        Self: 'a;
+
+    async fn foo(&self) -> Self::Fut<'a>;
+    //~^ ERROR use of undeclared lifetime name `'a`
+    //~| ERROR the parameter type `Self` may not live long enough
+}
+
+impl MyTrait for i32 {
+    type Fut<'a> = impl Future + 'a
+    where
+        Self: 'a;
+    //~^^^ ERROR `impl Trait` in type aliases is unstable
+
+    fn foo<'a>(&'a self) -> Self::Fut<'a> {
+        async {
+            *self
+        }
+    }
+}
+
+fn main() {}

src/test/ui/async-await/in-trait/async-associated-types2-desugared.stderr

@@ -0,0 +1,42 @@
+error[E0261]: use of undeclared lifetime name `'a`
+  --> $DIR/async-associated-types2-desugared.rs:13:38
+   |
+LL |     async fn foo(&self) -> Self::Fut<'a>;
+   |                                      ^^ undeclared lifetime
+   |
+help: consider introducing lifetime `'a` here
+   |
+LL |     async fn foo<'a>(&self) -> Self::Fut<'a>;
+   |                 ++++
+help: consider introducing lifetime `'a` here
+   |
+LL | trait MyTrait<'a> {
+   |              ++++
+
+error[E0658]: `impl Trait` in type aliases is unstable
+  --> $DIR/async-associated-types2-desugared.rs:19:20
+   |
+LL |     type Fut<'a> = impl Future + 'a
+   |                    ^^^^^^^^^^^^^^^^
+   |
+   = note: see issue #63063 <https://github.com/rust-lang/rust/issues/63063> for more information
+   = help: add `#![feature(type_alias_impl_trait)]` to the crate attributes to enable
+
+error[E0310]: the parameter type `Self` may not live long enough
+  --> $DIR/async-associated-types2-desugared.rs:13:28
+   |
+LL |     async fn foo(&self) -> Self::Fut<'a>;
+   |                            ^^^^^^^^^^^^^
+   |
+   = help: consider adding an explicit lifetime bound `Self: 'static`...
+   = note: ...so that the type `Self` will meet its required lifetime bounds...
+note: ...that is required by this bound
+  --> $DIR/async-associated-types2-desugared.rs:11:15
+   |
+LL |         Self: 'a;
+   |               ^^
+
+error: aborting due to 3 previous errors
+
+Some errors have detailed explanations: E0261, E0310, E0658.
+For more information about an error, try `rustc --explain E0261`.

src/test/ui/async-await/in-trait/async-associated-types2.rs

@@ -0,0 +1,32 @@
+// edition: 2021
+
+#![feature(async_fn_in_trait)]
+#![allow(incomplete_features)]
+
+use std::future::Future;
+
+trait MyTrait {
+    type Fut<'a>: Future<Output = i32>
+    where
+        Self: 'a;
+
+    fn foo(&self) -> Self::Fut<'a>;
+    //~^ ERROR use of undeclared lifetime name `'a`
+}
+
+impl MyTrait for i32 {
+    type Fut<'a> = impl Future + 'a
+    where
+        Self: 'a;
+    //~^^^ ERROR `impl Trait` in type aliases is unstable
+    //~| ERROR expected `<i32 as MyTrait>::Fut<'a>` to be a future that resolves to `i32`, but it resolves to `<<i32 as MyTrait>::Fut<'a> as Future>::Output`
+
+    fn foo<'a>(&'a self) -> Self::Fut<'a> {
+        //~^ ERROR `impl` item signature doesn't match `trait` item signature
+        async {
+            *self
+        }
+    }
+}
+
+fn main() {}

src/test/ui/async-await/in-trait/async-associated-types2.stderr

@@ -0,0 +1,63 @@
+error[E0261]: use of undeclared lifetime name `'a`
+  --> $DIR/async-associated-types2.rs:13:32
+   |
+LL |     fn foo(&self) -> Self::Fut<'a>;
+   |                                ^^ undeclared lifetime
+   |
+help: consider introducing lifetime `'a` here
+   |
+LL |     fn foo<'a>(&self) -> Self::Fut<'a>;
+   |           ++++
+help: consider introducing lifetime `'a` here
+   |
+LL | trait MyTrait<'a> {
+   |              ++++
+
+error[E0658]: `impl Trait` in type aliases is unstable
+  --> $DIR/async-associated-types2.rs:18:20
+   |
+LL |     type Fut<'a> = impl Future + 'a
+   |                    ^^^^^^^^^^^^^^^^
+   |
+   = note: see issue #63063 <https://github.com/rust-lang/rust/issues/63063> for more information
+   = help: add `#![feature(type_alias_impl_trait)]` to the crate attributes to enable
+
+error[E0271]: expected `<i32 as MyTrait>::Fut<'a>` to be a future that resolves to `i32`, but it resolves to `<<i32 as MyTrait>::Fut<'a> as Future>::Output`
+  --> $DIR/async-associated-types2.rs:18:20
+   |
+LL |     type Fut<'a> = impl Future + 'a
+   |                    ^^^^^^^^^^^^^^^^ expected `i32`, found associated type
+   |
+   = note:         expected type `i32`
+           found associated type `<<i32 as MyTrait>::Fut<'a> as Future>::Output`
+note: required by a bound in `MyTrait::Fut`
+  --> $DIR/async-associated-types2.rs:9:26
+   |
+LL |     type Fut<'a>: Future<Output = i32>
+   |                          ^^^^^^^^^^^^ required by this bound in `MyTrait::Fut`
+help: consider constraining the associated type `<<i32 as MyTrait>::Fut<'a> as Future>::Output` to `i32`
+   |
+LL |     type Fut<'a> = impl Future<Output = i32> + 'a
+   |                               ++++++++++++++
+
+error: `impl` item signature doesn't match `trait` item signature
+  --> $DIR/async-associated-types2.rs:24:5
+   |
+LL |     fn foo(&self) -> Self::Fut<'a>;
+   |     ------------------------------- expected `fn(&'1 i32) -> <i32 as MyTrait>::Fut<'static>`
+...
+LL |     fn foo<'a>(&'a self) -> Self::Fut<'a> {
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ found `fn(&'1 i32) -> <i32 as MyTrait>::Fut<'1>`
+   |
+   = note: expected `fn(&'1 i32) -> <i32 as MyTrait>::Fut<'static>`
+              found `fn(&'1 i32) -> <i32 as MyTrait>::Fut<'1>`
+help: the lifetime requirements from the `impl` do not correspond to the requirements in the `trait`
+  --> $DIR/async-associated-types2.rs:13:22
+   |
+LL |     fn foo(&self) -> Self::Fut<'a>;
+   |                      ^^^^ consider borrowing this type parameter in the trait
+
+error: aborting due to 4 previous errors
+
+Some errors have detailed explanations: E0261, E0271, E0658.
+For more information about an error, try `rustc --explain E0261`.

src/test/ui/async-await/in-trait/async-example.rs

@@ -0,0 +1,17 @@
+// check-pass
+// edition: 2021
+
+#![feature(async_fn_in_trait)]
+#![allow(incomplete_features)]
+
+trait MyTrait {
+    async fn foo(&self) -> i32;
+}
+
+impl MyTrait for i32 {
+    async fn foo(&self) -> i32 {
+        *self
+    }
+}
+
+fn main() {}

src/test/ui/async-await/in-trait/async-generics-and-bounds.rs

@@ -0,0 +1,21 @@
+// edition: 2021
+
+#![feature(async_fn_in_trait)]
+#![allow(incomplete_features)]
+
+use std::fmt::Debug;
+use std::hash::Hash;
+
+trait MyTrait<T, U> {
+    async fn foo(&self) -> &(T, U) where T: Debug + Sized, U: Hash;
+}
+//~^^ ERROR the parameter type `U` may not live long enough
+//~| ERROR the parameter type `T` may not live long enough
+
+impl<T, U> MyTrait<T, U> for (T, U) {
+    async fn foo(&self) -> &(T, U) {
+        self
+    }
+}
+
+fn main() {}

src/test/ui/async-await/in-trait/async-generics-and-bounds.stderr

@@ -0,0 +1,37 @@
+error[E0311]: the parameter type `U` may not live long enough
+  --> $DIR/async-generics-and-bounds.rs:10:28
+   |
+LL |     async fn foo(&self) -> &(T, U) where T: Debug + Sized, U: Hash;
+   |                            ^^^^^^^
+   |
+note: the parameter type `U` must be valid for the anonymous lifetime as defined here...
+  --> $DIR/async-generics-and-bounds.rs:10:18
+   |
+LL |     async fn foo(&self) -> &(T, U) where T: Debug + Sized, U: Hash;
+   |                  ^
+note: ...so that the reference type `&(T, U)` does not outlive the data it points at
+  --> $DIR/async-generics-and-bounds.rs:10:28
+   |
+LL |     async fn foo(&self) -> &(T, U) where T: Debug + Sized, U: Hash;
+   |                            ^^^^^^^
+
+error[E0311]: the parameter type `T` may not live long enough
+  --> $DIR/async-generics-and-bounds.rs:10:28
+   |
+LL |     async fn foo(&self) -> &(T, U) where T: Debug + Sized, U: Hash;
+   |                            ^^^^^^^
+   |
+note: the parameter type `T` must be valid for the anonymous lifetime as defined here...
+  --> $DIR/async-generics-and-bounds.rs:10:18
+   |
+LL |     async fn foo(&self) -> &(T, U) where T: Debug + Sized, U: Hash;
+   |                  ^
+note: ...so that the reference type `&(T, U)` does not outlive the data it points at
+  --> $DIR/async-generics-and-bounds.rs:10:28
+   |
+LL |     async fn foo(&self) -> &(T, U) where T: Debug + Sized, U: Hash;
+   |                            ^^^^^^^
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0311`.

src/test/ui/async-await/in-trait/async-generics.rs

@@ -0,0 +1,18 @@
+// edition: 2021
+
+#![feature(async_fn_in_trait)]
+#![allow(incomplete_features)]
+
+trait MyTrait<T, U> {
+    async fn foo(&self) -> &(T, U);
+}
+//~^^ ERROR the parameter type `U` may not live long enough
+//~| ERROR the parameter type `T` may not live long enough
+
+impl<T, U> MyTrait<T, U> for (T, U) {
+    async fn foo(&self) -> &(T, U) {
+        self
+    }
+}
+
+fn main() {}

src/test/ui/async-await/in-trait/async-generics.stderr

@@ -0,0 +1,37 @@
+error[E0311]: the parameter type `U` may not live long enough
+  --> $DIR/async-generics.rs:7:28
+   |
+LL |     async fn foo(&self) -> &(T, U);
+   |                            ^^^^^^^
+   |
+note: the parameter type `U` must be valid for the anonymous lifetime as defined here...
+  --> $DIR/async-generics.rs:7:18
+   |
+LL |     async fn foo(&self) -> &(T, U);
+   |                  ^
+note: ...so that the reference type `&(T, U)` does not outlive the data it points at
+  --> $DIR/async-generics.rs:7:28
+   |
+LL |     async fn foo(&self) -> &(T, U);
+   |                            ^^^^^^^
+
+error[E0311]: the parameter type `T` may not live long enough
+  --> $DIR/async-generics.rs:7:28
+   |
+LL |     async fn foo(&self) -> &(T, U);
+   |                            ^^^^^^^
+   |
+note: the parameter type `T` must be valid for the anonymous lifetime as defined here...
+  --> $DIR/async-generics.rs:7:18
+   |
+LL |     async fn foo(&self) -> &(T, U);
+   |                  ^
+note: ...so that the reference type `&(T, U)` does not outlive the data it points at
+  --> $DIR/async-generics.rs:7:28
+   |
+LL |     async fn foo(&self) -> &(T, U);
+   |                            ^^^^^^^
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0311`.

src/test/ui/async-await/in-trait/async-lifetimes-and-bounds.rs

@@ -0,0 +1,20 @@
+// edition: 2021
+
+#![feature(async_fn_in_trait)]
+#![allow(incomplete_features)]
+
+use std::fmt::Debug;
+
+trait MyTrait<'a, 'b, T> {
+    async fn foo(&'a self, key: &'b T) -> (&'a Self, &'b T) where T: Debug + Sized;
+}
+//~^^ ERROR  the parameter type `Self` may not live long enough
+//~| ERROR the parameter type `T` may not live long enough
+
+impl<'a, 'b, T, U> MyTrait<'a, 'b, T> for U {
+    async fn foo(&'a self, key: &'b T) -> (&'a U, &'b T) {
+        (self, key)
+    }
+}
+
+fn main() {}

src/test/ui/async-await/in-trait/async-lifetimes-and-bounds.stderr

@@ -0,0 +1,23 @@
+error[E0309]: the parameter type `Self` may not live long enough
+  --> $DIR/async-lifetimes-and-bounds.rs:9:43
+   |
+LL |     async fn foo(&'a self, key: &'b T) -> (&'a Self, &'b T) where T: Debug + Sized;
+   |                                           ^^^^^^^^^^^^^^^^^
+   |
+   = help: consider adding an explicit lifetime bound `Self: 'a`...
+   = note: ...so that the reference type `&'a Self` does not outlive the data it points at
+
+error[E0309]: the parameter type `T` may not live long enough
+  --> $DIR/async-lifetimes-and-bounds.rs:9:43
+   |
+LL |     async fn foo(&'a self, key: &'b T) -> (&'a Self, &'b T) where T: Debug + Sized;
+   |                                           ^^^^^^^^^^^^^^^^^ ...so that the reference type `&'b T` does not outlive the data it points at
+   |
+help: consider adding an explicit lifetime bound...
+   |
+LL | trait MyTrait<'a, 'b, T: 'b> {
+   |                        ++++
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0309`.

src/test/ui/async-await/in-trait/async-lifetimes.rs

@@ -0,0 +1,18 @@
+// edition: 2021
+
+#![feature(async_fn_in_trait)]
+#![allow(incomplete_features)]
+
+trait MyTrait<'a, 'b, T> {
+    async fn foo(&'a self, key: &'b T) -> (&'a Self, &'b T);
+}
+//~^^ ERROR the parameter type `Self` may not live long enough
+//~| ERROR the parameter type `T` may not live long enough
+
+impl<'a, 'b, T, U> MyTrait<'a, 'b, T> for U {
+    async fn foo(&'a self, key: &'b T) -> (&'a U, &'b T) {
+        (self, key)
+    }
+}
+
+fn main() {}

src/test/ui/async-await/in-trait/async-lifetimes.stderr

@@ -0,0 +1,23 @@
+error[E0309]: the parameter type `Self` may not live long enough
+  --> $DIR/async-lifetimes.rs:7:43
+   |
+LL |     async fn foo(&'a self, key: &'b T) -> (&'a Self, &'b T);
+   |                                           ^^^^^^^^^^^^^^^^^
+   |
+   = help: consider adding an explicit lifetime bound `Self: 'a`...
+   = note: ...so that the reference type `&'a Self` does not outlive the data it points at
+
+error[E0309]: the parameter type `T` may not live long enough
+  --> $DIR/async-lifetimes.rs:7:43
+   |
+LL |     async fn foo(&'a self, key: &'b T) -> (&'a Self, &'b T);
+   |                                           ^^^^^^^^^^^^^^^^^ ...so that the reference type `&'b T` does not outlive the data it points at
+   |
+help: consider adding an explicit lifetime bound...
+   |
+LL | trait MyTrait<'a, 'b, T: 'b> {
+   |                        ++++
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0309`.

src/test/ui/async-await/in-trait/fn-not-async-err.rs

@@ -0,0 +1,17 @@
+// edition: 2021
+
+#![feature(async_fn_in_trait)]
+#![allow(incomplete_features)]
+
+trait MyTrait {
+    async fn foo(&self) -> i32;
+}
+
+impl MyTrait for i32 {
+    fn foo(&self) -> i32 {
+        //~^ ERROR: `i32` is not a future [E0277]
+        *self
+    }
+}
+
+fn main() {}

src/test/ui/async-await/in-trait/fn-not-async-err.stderr

@@ -0,0 +1,17 @@
+error[E0277]: `i32` is not a future
+  --> $DIR/fn-not-async-err.rs:11:22
+   |
+LL |     fn foo(&self) -> i32 {
+   |                      ^^^ `i32` is not a future
+   |
+   = help: the trait `Future` is not implemented for `i32`
+   = note: i32 must be a future or must implement `IntoFuture` to be awaited
+note: required by a bound in `MyTrait::foo::{opaque#0}`
+  --> $DIR/fn-not-async-err.rs:7:28
+   |
+LL |     async fn foo(&self) -> i32;
+   |                            ^^^ required by this bound in `MyTrait::foo::{opaque#0}`
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0277`.

src/test/ui/async-await/in-trait/fn-not-async-err2.rs

@@ -0,0 +1,21 @@
+// edition: 2021
+
+#![feature(async_fn_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> {
+        //~^ ERROR `impl Trait` only allowed in function and inherent method return types, not in `impl` method return [E0562]
+        async {
+            *self
+        }
+    }
+}
+
+fn main() {}

src/test/ui/async-await/in-trait/fn-not-async-err2.stderr

@@ -0,0 +1,12 @@
+error[E0562]: `impl Trait` only allowed in function and inherent method return types, not in `impl` method return
+  --> $DIR/fn-not-async-err2.rs:13:22
+   |
+LL |     fn foo(&self) -> impl Future<Output = i32> {
+   |                      ^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: see issue #91611 <https://github.com/rust-lang/rust/issues/91611> for more information
+   = help: add `#![feature(return_position_impl_trait_in_trait)]` to the crate attributes to enable
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0562`.