stabilize const mem::forget #73887

DutchGhost · 2020-06-30T08:56:25Z

Stabilizes const mem::forget as implemented in #69617 and tracked in #69616.

Closes #69616

rust-highfive · 2020-06-30T08:56:29Z

r? @withoutboats

(rust_highfive has picked a reviewer for you, use r? to override)

DutchGhost · 2020-06-30T09:04:46Z

r? @Amanieu
cc @https://github.com/orgs/rust-lang/teams/wg-const-eval, @oli-obk

oli-obk · 2020-06-30T09:17:57Z

cc @rust-lang/wg-const-eval

RalfJung

LGTM (with CI failure fixed)

Amanieu · 2020-07-01T01:20:03Z

@rfcbot fcp merge

rfcbot · 2020-07-01T01:20:04Z

Team member @Amanieu 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.

rfcbot · 2020-07-01T06:05:09Z

🔔 This is now entering its final comment period, as per the review above. 🔔

petertodd · 2020-07-02T04:56:48Z

Question: we also have forget_unsized(), with the intention of removing the sized bound on forget() eventually.

Will unsized locals be const-compatible? I'd assume so. But if not this might be a problem.

RalfJung · 2020-07-02T06:47:08Z

Miri already supports unsized locals. So the underlying CTFE engine is ready. It is just a matter of adjusting the const checks to accept such code.

petertodd · 2020-07-02T07:06:14Z

Miri already supports unsized locals. So the underlying CTFE engine is ready. It is just a matter of adjusting the const checks to accept such code.

Great! That definitely eliminates my concern.

rfcbot · 2020-07-11T06:16:35Z

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.

oli-obk · 2020-07-11T06:21:36Z

@bors r+

bors · 2020-07-11T06:21:37Z

📌 Commit a065096 has been approved by oli-obk

@ghost

…arth Rollup of 19 pull requests Successful merges: - rust-lang#71322 (Accept tuple.0.0 as tuple indexing (take 2)) - rust-lang#72303 (Add core::future::{poll_fn, PollFn}) - rust-lang#73862 (Stabilize casts and coercions to `&[T]` in const fn) - rust-lang#73887 (stabilize const mem::forget) - rust-lang#73989 (adjust ub-enum test to be endianess-independent) - rust-lang#74045 (Explain effects of debugging options from config.toml) - rust-lang#74076 (Add `read_exact_at` and `write_all_at` to WASI's `FileExt`) - rust-lang#74099 (Add VecDeque::range* methods) - rust-lang#74100 (Use str::strip* in bootstrap) - rust-lang#74103 (Only add CFGuard on `windows-msvc` targets) - rust-lang#74109 (Only allow `repr(i128/u128)` on enum) - rust-lang#74122 (Start-up clean-up) - rust-lang#74125 (Correctly mark the ending span of a match arm) - rust-lang#74127 (Avoid "whitelist") - rust-lang#74129 (:arrow_up: rust-analyzer) - rust-lang#74135 (Update books) - rust-lang#74145 (Update rust-installer to latest version) - rust-lang#74161 (Fix disabled dockerfiles) - rust-lang#74162 (take self by value in ToPredicate) Failed merges: r? @ghost

according to various people on tech-pkg@, there are no problems with the Firefox build Version 1.46.0 (2020-08-27) ========================== Language -------- - [`if`, `match`, and `loop` expressions can now be used in const functions.][72437] - [Additionally you are now also able to coerce and cast to slices (`&[T]`) in const functions.][73862] - [The `#[track_caller]` attribute can now be added to functions to use the function's caller's location information for panic messages.][72445] - [Recursively indexing into tuples no longer needs parentheses.][71322] E.g. `x.0.0` over `(x.0).0`. - [`mem::transmute` can now be used in static and constants.][72920] **Note** You currently can't use `mem::transmute` in constant functions. Compiler -------- - [You can now use the `cdylib` target on Apple iOS and tvOS platforms.][73516] - [Enabled static "Position Independent Executables" by default for `x86_64-unknown-linux-musl`.][70740] Libraries --------- - [`mem::forget` is now a `const fn`.][73887] - [`String` now implements `From<char>`.][73466] - [The `leading_ones`, and `trailing_ones` methods have been stabilised for all integer types.][73032] - [`vec::IntoIter<T>` now implements `AsRef<[T]>`.][72583] - [All non-zero integer types (`NonZeroU8`) now implement `TryFrom` for their zero-able equivalent (e.g. `TryFrom<u8>`).][72717] - [`&[T]` and `&mut [T]` now implement `PartialEq<Vec<T>>`.][71660] - [`(String, u16)` now implements `ToSocketAddrs`.][73007] - [`vec::Drain<'_, T>` now implements `AsRef<[T]>`.][72584] Stabilized APIs --------------- - [`Option::zip`] - [`vec::Drain::as_slice`] Cargo ----- Added a number of new environment variables that are now available when compiling your crate. - [`CARGO_BIN_NAME` and `CARGO_CRATE_NAME`][cargo/8270] Providing the name of the specific binary being compiled and the name of the crate. - [`CARGO_PKG_LICENSE`][cargo/8325] The license from the manifest of the package. - [`CARGO_PKG_LICENSE_FILE`][cargo/8387] The path to the license file. Compatibility Notes ------------------- - [The target configuration option `abi_blacklist` has been renamed to `unsupported_abis`.][74150] The old name will still continue to work. - [Rustc will now warn if you cast a C-like enum that implements `Drop`.][72331] This was previously accepted but will become a hard error in a future release. - [Rustc will fail to compile if you have a struct with `#[repr(i128)]` or `#[repr(u128)]`.][74109] This representation is currently only allowed on `enum`s. - [Tokens passed to `macro_rules!` are now always captured.][73293] This helps ensure that spans have the correct information, and may cause breakage if you were relying on receiving spans with dummy information. - [The InnoSetup installer for Windows is no longer available.][72569] This was a legacy installer that was replaced by a MSI installer a few years ago but was still being built. - [`{f32, f64}::asinh` now returns the correct values for negative numbers.][72486] - [Rustc will no longer accept overlapping trait implementations that only differ in how the lifetime was bound.][72493] - [Rustc now correctly relates the lifetime of an existential associated type.][71896] This fixes some edge cases where `rustc` would erroneously allow you to pass a shorter lifetime than expected. - [Rustc now dynamically links to `libz` (also called `zlib`) on Linux.][74420] The library will need to be installed for `rustc` to work, even though we expect it to be already available on most systems. - [Tests annotated with `#[should_panic]` are broken on ARMv7 while running under QEMU.][74820] - [Pretty printing of some tokens in procedural macros changed.][75453] The exact output returned by rustc's pretty printing is an unstable implementation detail: we recommend any macro relying on it to switch to a more robust parsing system. [75453]: rust-lang/rust#75453 [74820]: rust-lang/rust#74820 [74420]: rust-lang/rust#74420 [74109]: rust-lang/rust#74109 [74150]: rust-lang/rust#74150 [73862]: rust-lang/rust#73862 [73887]: rust-lang/rust#73887 [73466]: rust-lang/rust#73466 [73516]: rust-lang/rust#73516 [73293]: rust-lang/rust#73293 [73007]: rust-lang/rust#73007 [73032]: rust-lang/rust#73032 [72920]: rust-lang/rust#72920 [72569]: rust-lang/rust#72569 [72583]: rust-lang/rust#72583 [72584]: rust-lang/rust#72584 [72717]: rust-lang/rust#72717 [72437]: rust-lang/rust#72437 [72445]: rust-lang/rust#72445 [72486]: rust-lang/rust#72486 [72493]: rust-lang/rust#72493 [72331]: rust-lang/rust#72331 [71896]: rust-lang/rust#71896 [71660]: rust-lang/rust#71660 [71322]: rust-lang/rust#71322 [70740]: rust-lang/rust#70740 [cargo/8270]: rust-lang/cargo#8270 [cargo/8325]: rust-lang/cargo#8325 [cargo/8387]: rust-lang/cargo#8387 [`Option::zip`]: https://doc.rust-lang.org/stable/std/option/enum.Option.html#method.zip [`vec::Drain::as_slice`]: https://doc.rust-lang.org/stable/std/vec/struct.Drain.html#method.as_slice

Pkgsrc changes: * Portability patches for Illumos have been intregrated upstream, so are no longer needed in pkgsrc. * Adjust one other patch, and update vendor/libc cargo checksum. Upstream changes: Version 1.46.0 (2020-08-27) ========================== Language -------- - [`if`, `match`, and `loop` expressions can now be used in const functions.] [72437] - [Additionally you are now also able to coerce and cast to slices (`&[T]`) in const functions.][73862] - [The `#[track_caller]` attribute can now be added to functions to use the function's caller's location information for panic messages.][72445] - [Recursively indexing into tuples no longer needs parentheses.][71322] E.g. `x.0.0` over `(x.0).0`. - [`mem::transmute` can now be used in static and constants.][72920] **Note** You currently can't use `mem::transmute` in constant functions. Compiler -------- - [You can now use the `cdylib` target on Apple iOS and tvOS platforms.][73516] - [Enabled static "Position Independent Executables" by default for `x86_64-unknown-linux-musl`.][70740] Libraries --------- - [`mem::forget` is now a `const fn`.][73887] - [`String` now implements `From<char>`.][73466] - [The `leading_ones`, and `trailing_ones` methods have been stabilised for all integer types.][73032] - [`vec::IntoIter<T>` now implements `AsRef<[T]>`.][72583] - [All non-zero integer types (`NonZeroU8`) now implement `TryFrom` for their zero-able equivalent (e.g. `TryFrom<u8>`).][72717] - [`&[T]` and `&mut [T]` now implement `PartialEq<Vec<T>>`.][71660] - [`(String, u16)` now implements `ToSocketAddrs`.][73007] - [`vec::Drain<'_, T>` now implements `AsRef<[T]>`.][72584] Stabilized APIs --------------- - [`Option::zip`] - [`vec::Drain::as_slice`] Cargo ----- Added a number of new environment variables that are now available when compiling your crate. - [`CARGO_BIN_NAME` and `CARGO_CRATE_NAME`][cargo/8270] Providing the name of the specific binary being compiled and the name of the crate. - [`CARGO_PKG_LICENSE`][cargo/8325] The license from the manifest of the package. - [`CARGO_PKG_LICENSE_FILE`][cargo/8387] The path to the license file. Compatibility Notes ------------------- - [The target configuration option `abi_blacklist` has been renamed to `unsupported_abis`.][74150] The old name will still continue to work. - [Rustc will now warn if you have a C-like enum that implements `Drop`.][72331] This was previously accepted but will become a hard error in a future release. - [Rustc will fail to compile if you have a struct with `#[repr(i128)]` or `#[repr(u128)]`.][74109] This representation is currently only allowed on `enum`s. - [Tokens passed to `macro_rules!` are now always captured.][73293] This helps ensure that spans have the correct information, and may cause breakage if you were relying on receiving spans with dummy information. - [The InnoSetup installer for Windows is no longer available.][72569] This was a legacy installer that was replaced by a MSI installer a few years ago but was still being built. - [`{f32, f64}::asinh` now returns the correct values for negative numbers.] [72486] - [Rustc will no longer accept overlapping trait implementations that only differ in how the lifetime was bound.][72493] - [Rustc now correctly relates the lifetime of an existential associated type.][71896] This fixes some edge cases where `rustc` would erroneously allow you to pass a shorter lifetime than expected. - [Rustc now dynamically links to `libz` (also called `zlib`) on Linux.][74420] The library will need to be installed for `rustc` to work, even though we expect it to be already available on most systems. - [Tests annotated with `#[should_panic]` are broken on ARMv7 while running under QEMU.][74820] - [Pretty printing of some tokens in procedural macros changed.][75453] The exact output returned by rustc's pretty printing is an unstable implementation detail: we recommend any macro relying on it to switch to a more robust parsing system. [75453]: rust-lang/rust#75453 [74820]: rust-lang/rust#74820 [74420]: rust-lang/rust#74420 [74109]: rust-lang/rust#74109 [74150]: rust-lang/rust#74150 [73862]: rust-lang/rust#73862 [73887]: rust-lang/rust#73887 [73466]: rust-lang/rust#73466 [73516]: rust-lang/rust#73516 [73293]: rust-lang/rust#73293 [73007]: rust-lang/rust#73007 [73032]: rust-lang/rust#73032 [72920]: rust-lang/rust#72920 [72569]: rust-lang/rust#72569 [72583]: rust-lang/rust#72583 [72584]: rust-lang/rust#72584 [72717]: rust-lang/rust#72717 [72437]: rust-lang/rust#72437 [72445]: rust-lang/rust#72445 [72486]: rust-lang/rust#72486 [72493]: rust-lang/rust#72493 [72331]: rust-lang/rust#72331 [71896]: rust-lang/rust#71896 [71660]: rust-lang/rust#71660 [71322]: rust-lang/rust#71322 [70740]: rust-lang/rust#70740 [cargo/8270]: rust-lang/cargo#8270 [cargo/8325]: rust-lang/cargo#8325 [cargo/8387]: rust-lang/cargo#8387 [`Option::zip`]: https://doc.rust-lang.org/stable/std/option/enum.Option.html#method.zip [`vec::Drain::as_slice`]: https://doc.rust-lang.org/stable/std/vec/struct.Drain.html#method.as_slice

rust-highfive assigned withoutboats Jun 30, 2020

rust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Jun 30, 2020

rust-highfive assigned Amanieu and unassigned withoutboats Jun 30, 2020

oli-obk added relnotes Marks issues that should be documented in the release notes of the next release. T-libs-api Relevant to the library API team, which will review and decide on the PR/issue. labels Jun 30, 2020

RalfJung approved these changes Jun 30, 2020

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stabilize const mem::forget

a065096

DutchGhost force-pushed the master branch from 66fea11 to a065096 Compare June 30, 2020 09:34

jonas-schievink added this to the 1.46 milestone Jun 30, 2020

rfcbot added the finished-final-comment-period The final comment period is finished for this PR / Issue. label Jul 11, 2020

rfcbot removed the final-comment-period In the final comment period and will be merged soon unless new substantive objections are raised. label Jul 11, 2020

bors 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 Jul 11, 2020

Manishearth mentioned this pull request Jul 11, 2020

Rollup of 19 pull requests #74235

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bors merged commit efda2b5 into rust-lang:master Jul 11, 2020

ratijas mentioned this pull request Sep 6, 2020

[tracking issue] const fn mem::forget #69616

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