bless suggestion on spell out

src/librustc_error_codes/error_codes.rs

@@ -435,7 +435,7 @@ E0750: include_str!("./error_codes/E0750.md"),
 E0751: include_str!("./error_codes/E0751.md"),
 E0752: include_str!("./error_codes/E0752.md"),
 E0753: include_str!("./error_codes/E0753.md"),
-E0754: include_str!("./error_codes/E0754.md"),
+E0755: include_str!("./error_codes/E0755.md"),
 ;
 //  E0006, // merged with E0005
 //  E0008, // cannot bind by-move into a pattern guard

src/librustc_error_codes/error_codes/E0755.md

@@ -1,4 +1,5 @@
-`async fn`/`impl trait` return type cannot contain a projection or `Self` that references lifetimes from a parent scope.
+`async fn`/`impl trait` return type cannot contain a projection
+or `Self` that references lifetimes from a parent scope.
 
 Erroneous code example:
 
@@ -24,6 +25,8 @@ impl<'a> S<'a> {
 }
 ```
 
-This will be allowed at some point in the future, but the implementation is not yet complete. See the [issue-61949] for this limitation.
+This will be allowed at some point in the future,
+but the implementation is not yet complete.
+See the [issue-61949] for this limitation.
 
 [issue-61949]: https://github.com/rust-lang/rust/issues/61949

src/librustc_typeck/check/mod.rs

@@ -1701,7 +1701,7 @@ fn check_opaque_for_inheriting_lifetimes(tcx: TyCtxt<'tcx>, def_id: LocalDefId,
         let mut err = struct_span_err!(
             tcx.sess,
             span,
-            E0754,
+            E0755,
             "`{}` return type cannot contain a projection or `Self` that references lifetimes from \
              a parent scope",
             if is_async { "async fn" } else { "impl Trait" },

src/test/ui/async-await/issue-61949-self-return-type.stderr

@@ -1,8 +1,9 @@
-error: `async fn` return type cannot contain a projection or `Self` that references lifetimes from a parent scope
+error[E0755]: `async fn` return type cannot contain a projection or `Self` that references lifetimes from a parent scope
   --> $DIR/issue-61949-self-return-type.rs:11:40
    |
 LL |     pub async fn new(_bar: &'a i32) -> Self {
-   |                                        ^^^^
+   |                                        ^^^^ help: consider spelling out the type instead: `Foo<'a>`
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0754`.

src/test/ui/async-await/issue-69276.stderr

@@ -1,8 +0,0 @@
-error: `async fn` return type cannot contain a projection or `Self` that references lifetimes from a parent scope
-  --> $DIR/issue-69276.rs:6:33
-   |
-LL |     async fn new(i: &'a i32) -> Self {
-   |                                 ^^^^
-
-error: aborting due to previous error
-

src/test/ui/impl-trait/bound-normalization-fail.stderr

@@ -20,7 +20,7 @@ help: consider constraining the associated type `<T as impl_trait::Trait>::Assoc
 LL |     fn foo_fail<T: Trait<Assoc = ()>>() -> impl FooLike<Output=T::Assoc> {
    |                         ^^^^^^^^^^^^
 
-error: `impl Trait` return type cannot contain a projection or `Self` that references lifetimes from a parent scope
+error[E0755]: `impl Trait` return type cannot contain a projection or `Self` that references lifetimes from a parent scope
   --> $DIR/bound-normalization-fail.rs:43:41
    |
 LL |     fn foo2_fail<'a, T: Trait<'a>>() -> impl FooLike<Output=T::Assoc> {
@@ -42,4 +42,5 @@ LL |     fn foo2_fail<'a, T: Trait<'a, Assoc = ()>>() -> impl FooLike<Output=T::
 
 error: aborting due to 3 previous errors; 1 warning emitted
 
-For more information about this error, try `rustc --explain E0271`.
+Some errors have detailed explanations: E0271, E0755.
+For more information about an error, try `rustc --explain E0271`.