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Allow parenthesis around inferred array lengths - #139641

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BoxyUwU:allow_parend_array_len_infer
Apr 11, 2025
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Allow parenthesis around inferred array lengths#139641
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BoxyUwU:allow_parend_array_len_infer

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@BoxyUwUBoxyUwU commented Apr 10, 2025

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In #135272 it was noticed that we weren't handling Vec<(((((_)))))> correctly under the new desugaring for generic_arg_infer, this had to be fixed in order to not regress stable code for types that should continue working. This has the side effect of also allowing the following to work:

#![feature(generic_arg_infer)]structBar<constN:usize>;fnmain(){let a:Bar<((_))> = Bar::<10>;}

However I did not make the same change for array lengths resulting in the following not compiling:

#![feature(generic_arg_infer)]fnmain(){let a:[u8;(((_)))] = [2;2];let a:[u8;2] = [2;(((((_)))))];}

This is rather inconsistent as parenthesis around _are supported for const args to non-arrays, and type args. This PR fixes this allowing the above example to compile. No stable impact.

r? compiler-errors

@rustbotrustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Apr 10, 2025
BoxyUwU
BoxyUwU commented Apr 10, 2025
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Comment threadtests/ui/const-generics/generic_arg_infer/parend_infer.rs
Comment on lines +16 to +17
#[rustfmt::skip]
let b: [u8; (_)] = [1; (((((_)))))];

@BoxyUwUBoxyUwUApr 10, 2025

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rustfmt wipes nested parenthesis in expressions so in order to make sure people dont accidentally format away part of the test..

compiler-errors
compiler-errors reviewed Apr 10, 2025
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Comment threadcompiler/rustc_ast_lowering/src/lib.rs
@BoxyUwU
BoxyUwUforce-pushed the allow_parend_array_len_infer branch 2 times, most recently from d9617ab to 95f90f3CompareApril 10, 2025 17:16
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compiler-errors approved these changes Apr 10, 2025
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wonderful!

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compiler-errors commented Apr 10, 2025

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@bors r+ rollup

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bors commented Apr 10, 2025

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📌 Commit 95f90f3 has been approved by compiler-errors

It is now in the queue for this repository.

@borsbors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Apr 10, 2025
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compiler-errors commented Apr 10, 2025•
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@bors r-

pls bless 🙏

@borsbors added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. labels Apr 10, 2025
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BoxyUwU commented Apr 10, 2025

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whatd I fuck up here :thonk:

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BoxyUwU commented Apr 10, 2025

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oh the rustfmt skip bumped line numbers

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BoxyUwUforce-pushed the allow_parend_array_len_infer branch from 95f90f3 to 8f00b1fCompareApril 10, 2025 17:59
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@bors r+ rollup

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📌 Commit 8f00b1f has been approved by compiler-errors

It is now in the queue for this repository.

@borsbors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Apr 10, 2025
@ZalatharZalathar mentioned this pull request Apr 11, 2025
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bors added a commit to rust-lang-ci/rust that referenced this pull request Apr 11, 2025
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Auto merge ofrust-lang#139657- Zalathar:rollup-6oh6f9q, r=Zalathar
18a029c
Rollup of 12 pull requests
Successful merges:
- rust-lang#137447 (add `core::intrinsics::simd::{simd_extract_dyn, simd_insert_dyn}`)
- rust-lang#138182 (rustc_target: update x86_win64 to match the documented calling convention for f128)
- rust-lang#138682 (Allow drivers to supply a list of extra symbols to intern)
- rust-lang#138904 (Test linking and running `no_std` binaries)
- rust-lang#138998 (Don't suggest the use of `impl Trait` in closure parameter)
- rust-lang#139447 (doc changes: debug assertions -> overflow checks)
- rust-lang#139469 (Introduce a `//@ needs-crate-type` compiletest directive)
- rust-lang#139564 (Deeply normalize obligations in `BestObligation` folder)
- rust-lang#139574 (bootstrap: improve `channel` handling)
- rust-lang#139600 (Update `compiler-builtins` to 0.1.153)
- rust-lang#139641 (Allow parenthesis around inferred array lengths)
- rust-lang#139654 (Improve `AssocItem::descr`.)
r? `@ghost`
`@rustbot` modify labels: rollup
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bors merged commit 25d282e into rust-lang:masterApr 11, 2025
@rustbotrustbot added this to the 1.88.0 milestone Apr 11, 2025
rust-timer added a commit to rust-lang-ci/rust that referenced this pull request Apr 11, 2025
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Unrolled build forrust-lang#139641
f630cdc
Rollup merge of rust-lang#139641 - BoxyUwU:allow_parend_array_len_infer, r=compiler-errors
Allow parenthesis around inferred array lengths
In rust-lang#135272 it was noticed that we weren't handling `Vec<(((((_)))))>` correctly under the new desugaring for `generic_arg_infer`, this had to be fixed in order to not regress stable code for types that should continue working. This has the side effect of *also* allowing the following to work:
```rust
#![feature(generic_arg_infer)]
struct Bar<const N: usize>;
fn main() {
let a: Bar<((_))> = Bar::<10>;
}
```
However I did not make the same change for array lengths resulting in the following not compiling:
```rust
#![feature(generic_arg_infer)]
fn main() {
let a: [u8; (((_)))] = [2; 2];
let a: [u8; 2] = [2; (((((_)))))];
}
```
This is rather inconsistent as parenthesis around `_` *are* supported for const args to non-arrays, and type args. This PR fixes this allowing the above example to compile. No stable impact.
r? compiler-errors
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