Update test output for stable Rust 2021.

src/test/ui/async-await/edition-deny-async-fns-2015.stderr

@@ -4,7 +4,7 @@ error[E0670]: `async fn` is not permitted in Rust 2015
 LL | async fn foo() {}
    | ^^^^^ to use `async fn`, switch to Rust 2018 or later
    |
-   = help: set `edition = "2018"` in `Cargo.toml`
+   = help: set `edition = "2021"` in `Cargo.toml`
    = note: for more on editions, read https://doc.rust-lang.org/edition-guide
 
 error[E0670]: `async fn` is not permitted in Rust 2015
@@ -13,7 +13,7 @@ error[E0670]: `async fn` is not permitted in Rust 2015
 LL | fn baz() { async fn foo() {} }
    |            ^^^^^ to use `async fn`, switch to Rust 2018 or later
    |
-   = help: set `edition = "2018"` in `Cargo.toml`
+   = help: set `edition = "2021"` in `Cargo.toml`
    = note: for more on editions, read https://doc.rust-lang.org/edition-guide
 
 error[E0670]: `async fn` is not permitted in Rust 2015
@@ -22,7 +22,7 @@ error[E0670]: `async fn` is not permitted in Rust 2015
 LL | async fn async_baz() {
    | ^^^^^ to use `async fn`, switch to Rust 2018 or later
    |
-   = help: set `edition = "2018"` in `Cargo.toml`
+   = help: set `edition = "2021"` in `Cargo.toml`
    = note: for more on editions, read https://doc.rust-lang.org/edition-guide
 
 error[E0670]: `async fn` is not permitted in Rust 2015
@@ -31,7 +31,7 @@ error[E0670]: `async fn` is not permitted in Rust 2015
 LL |     async fn bar() {}
    |     ^^^^^ to use `async fn`, switch to Rust 2018 or later
    |
-   = help: set `edition = "2018"` in `Cargo.toml`
+   = help: set `edition = "2021"` in `Cargo.toml`
    = note: for more on editions, read https://doc.rust-lang.org/edition-guide
 
 error[E0670]: `async fn` is not permitted in Rust 2015
@@ -40,7 +40,7 @@ error[E0670]: `async fn` is not permitted in Rust 2015
 LL |     async fn foo() {}
    |     ^^^^^ to use `async fn`, switch to Rust 2018 or later
    |
-   = help: set `edition = "2018"` in `Cargo.toml`
+   = help: set `edition = "2021"` in `Cargo.toml`
    = note: for more on editions, read https://doc.rust-lang.org/edition-guide
 
 error[E0670]: `async fn` is not permitted in Rust 2015
@@ -49,7 +49,7 @@ error[E0670]: `async fn` is not permitted in Rust 2015
 LL |     async fn foo() {}
    |     ^^^^^ to use `async fn`, switch to Rust 2018 or later
    |
-   = help: set `edition = "2018"` in `Cargo.toml`
+   = help: set `edition = "2021"` in `Cargo.toml`
    = note: for more on editions, read https://doc.rust-lang.org/edition-guide
 
 error[E0670]: `async fn` is not permitted in Rust 2015
@@ -58,7 +58,7 @@ error[E0670]: `async fn` is not permitted in Rust 2015
 LL |         async fn bar() {}
    |         ^^^^^ to use `async fn`, switch to Rust 2018 or later
    |
-   = help: set `edition = "2018"` in `Cargo.toml`
+   = help: set `edition = "2021"` in `Cargo.toml`
    = note: for more on editions, read https://doc.rust-lang.org/edition-guide
 
 error[E0670]: `async fn` is not permitted in Rust 2015
@@ -67,7 +67,7 @@ error[E0670]: `async fn` is not permitted in Rust 2015
 LL |         async fn foo() {}
    |         ^^^^^ to use `async fn`, switch to Rust 2018 or later
    |
-   = help: set `edition = "2018"` in `Cargo.toml`
+   = help: set `edition = "2021"` in `Cargo.toml`
    = note: for more on editions, read https://doc.rust-lang.org/edition-guide
 
 error[E0670]: `async fn` is not permitted in Rust 2015
@@ -76,7 +76,7 @@ error[E0670]: `async fn` is not permitted in Rust 2015
 LL |             async fn bar() {}
    |             ^^^^^ to use `async fn`, switch to Rust 2018 or later
    |
-   = help: set `edition = "2018"` in `Cargo.toml`
+   = help: set `edition = "2021"` in `Cargo.toml`
    = note: for more on editions, read https://doc.rust-lang.org/edition-guide
 
 error[E0706]: functions in traits cannot be declared `async`

src/test/ui/async-await/suggest-switching-edition-on-await.rs

@@ -10,7 +10,7 @@ fn await_on_struct_missing() {
     //~^ ERROR no field `await` on type
     //~| NOTE unknown field
     //~| NOTE to `.await` a `Future`, switch to Rust 2018
-    //~| HELP set `edition = "2018"` in `Cargo.toml`
+    //~| HELP set `edition = "2021"` in `Cargo.toml`
     //~| NOTE for more on editions, read https://doc.rust-lang.org/edition-guide
 }
 
@@ -23,7 +23,7 @@ struct S {
     //~^ ERROR no field `await` on type
     //~| HELP a field with a similar name exists
     //~| NOTE to `.await` a `Future`, switch to Rust 2018
-    //~| HELP set `edition = "2018"` in `Cargo.toml`
+    //~| HELP set `edition = "2021"` in `Cargo.toml`
     //~| NOTE for more on editions, read https://doc.rust-lang.org/edition-guide
 }
 
@@ -32,7 +32,7 @@ fn await_on_63533(x: Pin<&mut dyn Future<Output = ()>>) {
     //~^ ERROR no field `await` on type
     //~| NOTE unknown field
     //~| NOTE to `.await` a `Future`, switch to Rust 2018
-    //~| HELP set `edition = "2018"` in `Cargo.toml`
+    //~| HELP set `edition = "2021"` in `Cargo.toml`
     //~| NOTE for more on editions, read https://doc.rust-lang.org/edition-guide
 }
 
@@ -40,6 +40,6 @@ fn await_on_apit(x: impl Future<Output = ()>) {
     x.await;
     //~^ ERROR no field `await` on type
     //~| NOTE to `.await` a `Future`, switch to Rust 2018
-    //~| HELP set `edition = "2018"` in `Cargo.toml`
+    //~| HELP set `edition = "2021"` in `Cargo.toml`
     //~| NOTE for more on editions, read https://doc.rust-lang.org/edition-guide
 }

src/test/ui/async-await/suggest-switching-edition-on-await.stderr

@@ -5,7 +5,7 @@ LL |     x.await;
    |       ^^^^^ unknown field
    |
    = note: to `.await` a `Future`, switch to Rust 2018 or later
-   = help: set `edition = "2018"` in `Cargo.toml`
+   = help: set `edition = "2021"` in `Cargo.toml`
    = note: for more on editions, read https://doc.rust-lang.org/edition-guide
 
 error[E0609]: no field `await` on type `await_on_struct_similar::S`
@@ -15,7 +15,7 @@ LL |     x.await;
    |       ^^^^^ help: a field with a similar name exists: `awai`
    |
    = note: to `.await` a `Future`, switch to Rust 2018 or later
-   = help: set `edition = "2018"` in `Cargo.toml`
+   = help: set `edition = "2021"` in `Cargo.toml`
    = note: for more on editions, read https://doc.rust-lang.org/edition-guide
 
 error[E0609]: no field `await` on type `Pin<&mut dyn Future<Output = ()>>`
@@ -25,7 +25,7 @@ LL |     x.await;
    |       ^^^^^ unknown field
    |
    = note: to `.await` a `Future`, switch to Rust 2018 or later
-   = help: set `edition = "2018"` in `Cargo.toml`
+   = help: set `edition = "2021"` in `Cargo.toml`
    = note: for more on editions, read https://doc.rust-lang.org/edition-guide
 
 error[E0609]: no field `await` on type `impl Future<Output = ()>`
@@ -35,7 +35,7 @@ LL |     x.await;
    |       ^^^^^
    |
    = note: to `.await` a `Future`, switch to Rust 2018 or later
-   = help: set `edition = "2018"` in `Cargo.toml`
+   = help: set `edition = "2021"` in `Cargo.toml`
    = note: for more on editions, read https://doc.rust-lang.org/edition-guide
 
 error: aborting due to 4 previous errors

src/test/ui/editions/async-block-2015.rs

 async fn foo() {
 //~^ ERROR `async fn` is not permitted in Rust 2015
 //~| NOTE to use `async fn`, switch to Rust 2018 or later
-//~| HELP set `edition = "2018"` in `Cargo.toml`
+//~| HELP set `edition = "2021"` in `Cargo.toml`
 //~| NOTE for more on editions, read https://doc.rust-lang.org/edition-guide
 
     let x = async {};
@@ -11,7 +11,7 @@ async fn foo() {
         let x = 42;
         //~^ ERROR expected identifier, found keyword `let`
         //~| NOTE expected identifier, found keyword
-        //~| HELP set `edition = "2018"` in `Cargo.toml`
+        //~| HELP set `edition = "2021"` in `Cargo.toml`
         //~| NOTE for more on editions, read https://doc.rust-lang.org/edition-guide
         42
     };
@@ -19,7 +19,7 @@ async fn foo() {
         42
         //~^ ERROR expected identifier, found `42`
         //~| NOTE expected identifier
-        //~| HELP set `edition = "2018"` in `Cargo.toml`
+        //~| HELP set `edition = "2021"` in `Cargo.toml`
         //~| NOTE for more on editions, read https://doc.rust-lang.org/edition-guide
     };
     y.await;

src/test/ui/editions/async-block-2015.stderr

@@ -4,7 +4,7 @@ error[E0670]: `async fn` is not permitted in Rust 2015
 LL | async fn foo() {
    | ^^^^^ to use `async fn`, switch to Rust 2018 or later
    |
-   = help: set `edition = "2018"` in `Cargo.toml`
+   = help: set `edition = "2021"` in `Cargo.toml`
    = note: for more on editions, read https://doc.rust-lang.org/edition-guide
 
 error: expected identifier, found keyword `let`
@@ -15,7 +15,7 @@ LL |     let y = async {
 LL |         let x = 42;
    |         ^^^ expected identifier, found keyword
    |
-   = help: set `edition = "2018"` in `Cargo.toml`
+   = help: set `edition = "2021"` in `Cargo.toml`
    = note: for more on editions, read https://doc.rust-lang.org/edition-guide
 
 error: expected identifier, found `42`
@@ -26,7 +26,7 @@ LL |     let z = async {
 LL |         42
    |         ^^ expected identifier
    |
-   = help: set `edition = "2018"` in `Cargo.toml`
+   = help: set `edition = "2021"` in `Cargo.toml`
    = note: for more on editions, read https://doc.rust-lang.org/edition-guide
 
 error[E0422]: cannot find struct, variant or union type `async` in this scope

src/test/ui/impl-trait/issues/issue-79099.stderr

@@ -6,7 +6,7 @@ LL |         let f: impl core::future::Future<Output = u8> = async { 1 };
    |                                                         |
    |                                                         `async` blocks are only allowed in Rust 2018 or later
    |
-   = help: set `edition = "2018"` in `Cargo.toml`
+   = help: set `edition = "2021"` in `Cargo.toml`
    = note: for more on editions, read https://doc.rust-lang.org/edition-guide
 
 error[E0562]: `impl Trait` not allowed outside of function and method return types