[ignore] testing #80428
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[ignore] testing #80428
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Co-authored-by: Jonas Schievink <jonasschievink@gmail.com> Co-authored-by: Vadim Petrochenkov <vadim.petrochenkov@gmail.com>
Co-authored-by: Jonas Schievink <jonasschievink@gmail.com>
…ds rather than the unique closure type in E0121 This is a squash of the titular commit along with these minor commits: - Improve note - Improve note pt2
This also adds back a comment that was mistakenly removed in ac9dfc3.
Update RELEASES.md for 1.49.0 ### [Rendered](https://github.com/XAMPPRocky/rust/tree/relnotes-1.49.0/RELEASES.md) r? `@Mark-Simulacrum` cc `@rust-lang/release`
Suggest fn ptr rather than fn item and suggest to use `Fn` trait bounds rather than the unique closure type in E0121
Previously, using `_` as a return type in a function that returned a function/closure would provide a diagnostic that would cause a papercut. For example:
```rust
fn f() -> i32 { 0 }
fn fn_ptr() -> _ { f }
fn closure() -> _ { || 0 }
```
would result in this diagnostic:
```rust
error[E0121]: the type placeholder `_` is not allowed within types on item signatures
--> <anon>:2:16
|
2 | fn fn_ptr() -> _ { f }
| ^
| |
| not allowed in type signatures
| help: replace with the correct return type: `fn() -> i32 {f}`
error[E0121]: the type placeholder `_` is not allowed within types on item signatures
--> <anon>:3:17
|
3 | fn closure() -> _ { || 0 }
| ^
| |
| not allowed in type signatures
| help: replace with the correct return type: `[closure@<anon>:3:21: 3:25]`
error: aborting due to 2 previous errors
For more information about this error, try `rustc --explain E0121`.
```
As can be seen, it was suggested to use the function definition return type `fn() -> i32 { f }` which is not valid syntax as a return type. Additionally, closures cause a papercut as unique closure types (notated in this case as `[closure@<anon>:3:21: 3:25]`) are not valid syntax either.
Instead, this PR implements this version of the diagnostic (this example is for the same code featured above):
```rust
error[E0121]: the type placeholder `_` is not allowed within types on item signatures
--> <anon>:2:16
|
2 | fn fn_ptr() -> _ { f }
| ^
| |
| not allowed in type signatures
| help: replace with the correct return type: `fn() -> i32`
error[E0121]: the type placeholder `_` is not allowed within types on item signatures
--> <anon>:3:17
|
3 | fn closure() -> _ { || 0 }
| ^ not allowed in type signatures
|
= help: consider using an `Fn`, `FnMut`, or `FnOnce` trait bound
= 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
For more information about this error, try `rustc --explain E0121`.
```
As can be seen in this diagnostic, the papercut for returning a function item is fixed by suggesting the usage of a function pointer as the return type. As for closures, it's suggested to use an `Fn`, `FnMut`, or `FnOnce` trait bound (with further reading on closures and `Fn` traits in *The Book* for beginners). I did not implement a suggestion to use `impl Fn() -> i32` syntax as that was out-of-scope for my abilities at the moment, therefore someone in the future may want to implement that. Also, it's possible to use either `impl Trait` syntax, generics, or generics with a `where` clause, and some users may not want to use `impl Trait` syntax for their own reasons.
This PR fixes #80179.
Add more comments to trait queries This also adds back a comment that was mistakenly removed in ac9dfc3.
use matches!() macro in more places
BTreeMap: test split_off (and append) more thoroughly Using DeterministicRng as a poor man's property based testing rig. r? `@Mark-Simulacrum`
Document rustc_macros on nightly-rustc Fixes #80345.   r? `@ehuss`
clarify wrapping ptr arithmetic docs Fixes #80306 `@steffahn` please let me know if this helps avoid the misunderstanding. :)
…acrum BTreeMap: rename the area access methods r? `@Mark-Simulacrum`
Add links to the source for the rustc and rustdoc books. This adds a little icon in the upper-right corner of the books so that readers can find the source if they want to make changes or file issues. This is already included in several of the other books.
Remove FIXME in rustc_privacy #71104 has been fixed. r? `@marmeladema` if you have time, otherwise `@petrochenkov`
fix: small typo error in chalk/mod.rs
rustdoc book: fix example `lib.rs` file is created only if `--lib` flag is specified
|
Error: Label rollup can only be set by Rust team members Please let |
|
Error: Label rollup can only be set by Rust team members Please let |
|
Just testing something, please ignore |
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This was just a failed test, please ignore it. Sorry if I wasted anyone's time :(