Update send not implemented to point to the block

Author: dtolnay

tests/ui/send-not-implemented.stderr

@@ -1,13 +1,18 @@
 error[E0277]: `std::sync::MutexGuard<'_, ()>` cannot be sent between threads safely
- --> $DIR/send-not-implemented.rs:6:1
-  |
-6 | #[async_trait]
-  | ^^^^^^^^^^^^^^ `std::sync::MutexGuard<'_, ()>` cannot be sent between threads safely
-  |
-  = help: within `impl std::future::Future`, the trait `std::marker::Send` is not implemented for `std::sync::MutexGuard<'_, ()>`
-  = note: required because it appears within the type `for<'r, 's> {&'r Self, std::sync::Mutex<()>, std::sync::MutexGuard<'s, ()>, impl std::future::Future, impl std::future::Future, ()}`
-  = note: required because it appears within the type `[static generator@$DIR/tests/ui/send-not-implemented.rs:8:26: 12:6 _self:&Self for<'r, 's> {&'r Self, std::sync::Mutex<()>, std::sync::MutexGuard<'s, ()>, impl std::future::Future, impl std::future::Future, ()}]`
-  = note: required because it appears within the type `std::future::GenFuture<[static generator@$DIR/tests/ui/send-not-implemented.rs:8:26: 12:6 _self:&Self for<'r, 's> {&'r Self, std::sync::Mutex<()>, std::sync::MutexGuard<'s, ()>, impl std::future::Future, impl std::future::Future, ()}]>`
-  = note: required because it appears within the type `impl std::future::Future`
-  = note: required because it appears within the type `impl std::future::Future`
-  = note: required for the cast to the object type `dyn std::future::Future<Output = ()> + std::marker::Send`
+  --> $DIR/send-not-implemented.rs:8:26
+   |
+8  |       async fn test(&self) {
+   |  __________________________^
+9  | |         let mutex = Mutex::new(());
+10 | |         let _guard = mutex.lock().unwrap();
+11 | |         f().await;
+12 | |     }
+   | |_____^ `std::sync::MutexGuard<'_, ()>` cannot be sent between threads safely
+   |
+   = help: within `impl std::future::Future`, the trait `std::marker::Send` is not implemented for `std::sync::MutexGuard<'_, ()>`
+   = note: required because it appears within the type `for<'r, 's> {&'r Self, std::sync::Mutex<()>, std::sync::MutexGuard<'s, ()>, impl std::future::Future, impl std::future::Future, ()}`
+   = note: required because it appears within the type `[static generator@$DIR/tests/ui/send-not-implemented.rs:8:26: 12:6 _self:&Self for<'r, 's> {&'r Self, std::sync::Mutex<()>, std::sync::MutexGuard<'s, ()>, impl std::future::Future, impl std::future::Future, ()}]`
+   = note: required because it appears within the type `std::future::GenFuture<[static generator@$DIR/tests/ui/send-not-implemented.rs:8:26: 12:6 _self:&Self for<'r, 's> {&'r Self, std::sync::Mutex<()>, std::sync::MutexGuard<'s, ()>, impl std::future::Future, impl std::future::Future, ()}]>`
+   = note: required because it appears within the type `impl std::future::Future`
+   = note: required because it appears within the type `impl std::future::Future`
+   = note: required for the cast to the object type `dyn std::future::Future<Output = ()> + std::marker::Send`