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Restore Fn trait note

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This commit is contained in:
Michael Goulet 2023-01-04 00:26:53 +00:00
parent a0390463fc
commit 89086f7d36
5 changed files with 17 additions and 5 deletions
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6
compiler/rustc_hir_analysis/src/collect.rs
View file

@ -1231,10 +1231,10 @@ fn infer_return_ty_for_fn_sig<'tcx>(
Applicability::MachineApplicable,
);
} else if ret_ty.is_closure() {
// We're dealing with a closure, so we should suggest using `impl Fn` or trait bounds
// to prevent the user from getting a papercut while trying to use the unique closure
// syntax (e.g. `[closure@src/lib.rs:2:5: 2:9]`).
diag.help("consider using an `Fn`, `FnMut`, or `FnOnce` trait bound");
}
// Also note how `Fn` traits work just in case!
if ret_ty.is_closure() {
diag.note(
"for more information on `Fn` traits and closure types, see \
https://doc.rust-lang.org/book/ch13-01-closures.html",

1
src/test/ui/fn/issue-80179.rs
View file

@ -20,6 +20,7 @@ fn returns_closure() -> _ {
//~| NOTE not allowed in type signatures
//~| HELP replace with an appropriate return type
//~| SUGGESTION impl Fn() -> i32
//~| NOTE for more information on `Fn` traits and closure types
|| 0
}

2
src/test/ui/fn/issue-80179.stderr
View file

@ -15,6 +15,8 @@ LL | fn returns_closure() -> _ {
| |
| not allowed in type signatures
| help: replace with an appropriate return type: `impl Fn() -> i32`
|
= note: for more information on `Fn` traits and closure types, see https://doc.rust-lang.org/book/ch13-01-closures.html
error: aborting due to 2 previous errors

3
src/test/ui/fn/suggest-return-closure.rs
View file

@ -3,6 +3,7 @@ fn fn_once() -> _ {
//~| NOTE not allowed in type signatures
//~| HELP replace with an appropriate return type
//~| SUGGESTION impl FnOnce()
//~| NOTE for more information on `Fn` traits and closure types
let x = String::new();
|| {
drop(x);
@ -14,6 +15,7 @@ fn fn_mut() -> _ {
//~| NOTE not allowed in type signatures
//~| HELP replace with an appropriate return type
//~| SUGGESTION impl FnMut(char)
//~| NOTE for more information on `Fn` traits and closure types
let x = String::new();
|c| {
x.push(c);
@ -25,6 +27,7 @@ fn fun() -> _ {
//~| NOTE not allowed in type signatures
//~| HELP replace with an appropriate return type
//~| SUGGESTION impl Fn() -> i32
//~| NOTE for more information on `Fn` traits and closure types
|| 1i32
}

10
src/test/ui/fn/suggest-return-closure.stderr
View file

@ -6,24 +6,30 @@ LL | fn fn_once() -> _ {
| |
| not allowed in type signatures
| help: replace with an appropriate return type: `impl FnOnce()`
|
= note: for more information on `Fn` traits and closure types, see https://doc.rust-lang.org/book/ch13-01-closures.html
error[E0121]: the placeholder `_` is not allowed within types on item signatures for return types
--> $DIR/suggest-return-closure.rs:12:16
--> $DIR/suggest-return-closure.rs:13:16
|
LL | fn fn_mut() -> _ {
| ^
| |
| not allowed in type signatures
| help: replace with an appropriate return type: `impl FnMut(char)`
|
= note: for more information on `Fn` traits and closure types, see https://doc.rust-lang.org/book/ch13-01-closures.html
error[E0121]: the placeholder `_` is not allowed within types on item signatures for return types
--> $DIR/suggest-return-closure.rs:23:13
--> $DIR/suggest-return-closure.rs:25:13
|
LL | fn fun() -> _ {
| ^
| |
| not allowed in type signatures
| help: replace with an appropriate return type: `impl Fn() -> i32`
|
= note: for more information on `Fn` traits and closure types, see https://doc.rust-lang.org/book/ch13-01-closures.html
error: aborting due to 3 previous errors