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Stabilize underscore_const_names in 1.37.0 #61347
Stabilize underscore_const_names in 1.37.0 #61347
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Stabilization proposalI propose that we stabilize @rfcbot merge Tracking issue: #54912 What is stabilizedYou are now permitted to write: const _: $type_expression = $term_expression; That is, we change the grammar of items, as written in the Item = attrs:OuterAttr* vis:Vis? kind:ItemKind;
ItemKind =
| ...
| Const:{ "const" name:IDENT ":" ty:Type "=" value:Expr ";" }
| ...
; into: Item = attrs:OuterAttr* vis:Vis? kind:ItemKind;
ItemKind =
| ...
| Const:{ "const" name:IdentOrUnderscore ":" ty:Type "=" value:Expr ";" }
| ...
;
IdentOrUnderscore =
| Named:IDENT
| NoName:"_"
; When What is not stabilized
Divergences from RFC and unresolved questionsNone. TestsThe tests can be primarily seen in the PR itself. Here are some of them: History
MotivationThe general motivation for #[allow(non_upper_case_globals)]
const _IMPL_ARBITRARY_FOR_MyType: () = {
impl proptest::arbitrary::Arbitrary for MyType {
...
}
}; Instead, it would be better to generate: const _: () = {
impl proptest::arbitrary::Arbitrary for MyType {
...
}
}; This not only has the advantage of generating less code, but also produces better diagnostics. Other motivational examples include:
More generally, Potential concernsThere is some concern that There is also some concern of how Some considered alternativesUnnamed modules,
|
Team member @Centril has proposed to merge this. The next step is review by the rest of the tagged team members: No concerns currently listed. Once a majority of reviewers approve (and at most 2 approvals are outstanding), this will enter its final comment period. If you spot a major issue that hasn't been raised at any point in this process, please speak up! See this document for info about what commands tagged team members can give me. |
N.B. Aaron is on leave so I've checked his box. |
Implementation LGMT, marking as waiting on team. |
🔔 This is now entering its final comment period, as per the review above. 🔔 |
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Looks like quite a hack to achieve the stated outcome. Reminds me of javascript. |
The final comment period, with a disposition to merge, as per the review above, is now complete. As the automated representative of the governance process, I would like to thank the author for their work and everyone else who contributed. The RFC will be merged soon. |
@bors r=petrochenkov |
📌 Commit e62c9d7 has been approved by |
…trochenkov Stabilize underscore_const_names in 1.37.0 You are now permitted to write: ```rust const _: $type_expression = $term_expression; ``` That is, we change the [grammar of items](https://github.com/rust-lang-nursery/wg-grammar/blob/9d1984d7ae8d6576f943566539a31a5800644c57/grammar/item.lyg#L3-L42), as written in [the *`.lyg`* notation](https://github.com/rust-lang/gll/tree/263bf161dad903e67aa65fc591ced3cab18afa2a#grammar), from: ```java Item = attrs:OuterAttr* vis:Vis? kind:ItemKind; ItemKind = | ... | Const:{ "const" name:IDENT ":" ty:Type "=" value:Expr ";" } | ... ; ``` into: ```java Item = attrs:OuterAttr* vis:Vis? kind:ItemKind; ItemKind = | ... | Const:{ "const" name:IdentOrUnderscore ":" ty:Type "=" value:Expr ";" } | ... ; IdentOrUnderscore = | Named:IDENT | NoName:"_" ; ``` r? @petrochenkov
☀️ Test successful - checks-travis, status-appveyor |
Thanks @Centril for putting in the work in getting this feature stabilized. With it, I should be able to release 1.0 of |
I think we have our own hacky version in |
The crate offers functionality outside of @eddyb I hope to make |
Pkgsrc changes: * Add a patch to llvm to deal with const dli_saddr. * Adapt two other patches. * Cross-build currently fails, so i386, powerpc and sparc64 bootstrap kits for 1.37.0 are built natively. Missing aarch64 hardware, so that's not available yet. * Bump bootstrap requirements to 1.36.0 except for armv7-unknown-netbsd-eabihf which I've not managed to cross-build. Upstream changes: Version 1.37.0 (2019-08-15) ========================== Language -------- - `#[must_use]` will now warn if the type is contained in a [tuple][61100], [`Box`][62228], or an [array][62235] and unused. - [You can now use the `cfg` and `cfg_attr` attributes on generic parameters.][61547] - [You can now use enum variants through type alias.][61682] e.g. You can write the following: ```rust type MyOption = Option<u8>; fn increment_or_zero(x: MyOption) -> u8 { match x { MyOption::Some(y) => y + 1, MyOption::None => 0, } } ``` - [You can now use `_` as an identifier for consts.][61347] e.g. You can write `const _: u32 = 5;`. - [You can now use `#[repr(align(X)]` on enums.][61229] - [The `?`/_"Kleene"_ macro operator is now available in the 2015 edition.][60932] Compiler -------- - [You can now enable Profile-Guided Optimization with the `-C profile-generate` and `-C profile-use` flags.][61268] For more information on how to use profile guided optimization, please refer to the [rustc book][rustc-book-pgo]. - [The `rust-lldb` wrapper script should now work again.][61827] Libraries --------- - [`mem::MaybeUninit<T>` is now ABI-compatible with `T`.][61802] Stabilized APIs --------------- - [`BufReader::buffer`] - [`BufWriter::buffer`] - [`Cell::from_mut`] - [`Cell<[T]>::as_slice_of_cells`][`Cell<slice>::as_slice_of_cells`] - [`DoubleEndedIterator::nth_back`] - [`Option::xor`] - [`Wrapping::reverse_bits`] - [`i128::reverse_bits`] - [`i16::reverse_bits`] - [`i32::reverse_bits`] - [`i64::reverse_bits`] - [`i8::reverse_bits`] - [`isize::reverse_bits`] - [`slice::copy_within`] - [`u128::reverse_bits`] - [`u16::reverse_bits`] - [`u32::reverse_bits`] - [`u64::reverse_bits`] - [`u8::reverse_bits`] - [`usize::reverse_bits`] Cargo ----- - [`Cargo.lock` files are now included by default when publishing executable crates with executables.][cargo/7026] - [You can now specify `default-run="foo"` in `[package]` to specify the default executable to use for `cargo run`.][cargo/7056] Misc ---- Compatibility Notes ------------------- - [Using `...` for inclusive range patterns will now warn by default.][61342] Please transition your code to using the `..=` syntax for inclusive ranges instead. - [Using a trait object without the `dyn` will now warn by default.][61203] Please transition your code to use `dyn Trait` for trait objects instead. [62228]: rust-lang/rust#62228 [62235]: rust-lang/rust#62235 [61802]: rust-lang/rust#61802 [61827]: rust-lang/rust#61827 [61547]: rust-lang/rust#61547 [61682]: rust-lang/rust#61682 [61268]: rust-lang/rust#61268 [61342]: rust-lang/rust#61342 [61347]: rust-lang/rust#61347 [61100]: rust-lang/rust#61100 [61203]: rust-lang/rust#61203 [61229]: rust-lang/rust#61229 [60932]: rust-lang/rust#60932 [cargo/7026]: rust-lang/cargo#7026 [cargo/7056]: rust-lang/cargo#7056 [`BufReader::buffer`]: https://doc.rust-lang.org/std/io/struct.BufReader.html#method.buffer [`BufWriter::buffer`]: https://doc.rust-lang.org/std/io/struct.BufWriter.html#method.buffer [`Cell::from_mut`]: https://doc.rust-lang.org/std/cell/struct.Cell.html#method.from_mut [`Cell<slice>::as_slice_of_cells`]: https://doc.rust-lang.org/std/cell/struct.Cell.html#method.as_slice_of_cells [`DoubleEndedIterator::nth_back`]: https://doc.rust-lang.org/std/iter/trait.DoubleEndedIterator.html#method.nth_back [`Option::xor`]: https://doc.rust-lang.org/std/option/enum.Option.html#method.xor [`RefCell::try_borrow_unguarded`]: https://doc.rust-lang.org/std/cell/struct.RefCell.html#method.try_borrow_unguarded [`Wrapping::reverse_bits`]: https://doc.rust-lang.org/std/num/struct.Wrapping.html#method.reverse_bits [`i128::reverse_bits`]: https://doc.rust-lang.org/std/primitive.i128.html#method.reverse_bits [`i16::reverse_bits`]: https://doc.rust-lang.org/std/primitive.i16.html#method.reverse_bits [`i32::reverse_bits`]: https://doc.rust-lang.org/std/primitive.i32.html#method.reverse_bits [`i64::reverse_bits`]: https://doc.rust-lang.org/std/primitive.i64.html#method.reverse_bits [`i8::reverse_bits`]: https://doc.rust-lang.org/std/primitive.i8.html#method.reverse_bits [`isize::reverse_bits`]: https://doc.rust-lang.org/std/primitive.isize.html#method.reverse_bits [`slice::copy_within`]: https://doc.rust-lang.org/std/primitive.slice.html#method.copy_within [`u128::reverse_bits`]: https://doc.rust-lang.org/std/primitive.u128.html#method.reverse_bits [`u16::reverse_bits`]: https://doc.rust-lang.org/std/primitive.u16.html#method.reverse_bits [`u32::reverse_bits`]: https://doc.rust-lang.org/std/primitive.u32.html#method.reverse_bits [`u64::reverse_bits`]: https://doc.rust-lang.org/std/primitive.u64.html#method.reverse_bits [`u8::reverse_bits`]: https://doc.rust-lang.org/std/primitive.u8.html#method.reverse_bits [`usize::reverse_bits`]: https://doc.rust-lang.org/std/primitive.usize.html#method.reverse_bits [rustc-book-pgo]: https://doc.rust-lang.org/rustc/profile-guided-optimization.html
You are now permitted to write:
That is, we change the grammar of items, as written in the
.lyg
notation, from:into:
r? @petrochenkov