`const`-stablilize `NonNull::as_ref` #102198

lukas-code · 2022-09-23T16:11:33Z

A bunch of pointer to reference methods have been made unstably const some time ago in #91823 under the feature gate const_ptr_as_ref.
Out of these, NonNull::as_ref can be implemented as a const fn in stable rust today, so i hereby propose to const stabilize this function only.

Tracking issue: #91822

@rustbot label +T-libs-api -T-libs

rustbot · 2022-09-23T16:11:36Z

Hey! It looks like you've submitted a new PR for the library teams!

If this PR contains changes to any rust-lang/rust public library APIs then please comment with @rustbot label +T-libs-api -T-libs to tag it appropriately. If this PR contains changes to any unstable APIs please edit the PR description to add a link to the relevant API Change Proposal or create one if you haven't already. If you're unsure where your change falls no worries, just leave it as is and the reviewer will take a look and make a decision to forward on if necessary.

Examples of T-libs-api changes:

Stabilizing library features
Introducing insta-stable changes such as new implementations of existing stable traits on existing stable types
Introducing new or changing existing unstable library APIs (excluding permanently unstable features / features without a tracking issue)
Changing public documentation in ways that create new stability guarantees
Changing observable runtime behavior of library APIs

rust-highfive · 2022-09-23T16:11:36Z

r? @thomcc

(rust-highfive has picked a reviewer for you, use r? to override)

thomcc · 2022-09-23T16:13:56Z

This seems fine to me but needs FCP, so I'll assign to someone on t-libs-api.

r? @joshtriplett @rustbot label +T-libs-api -T-libs

joshtriplett · 2022-10-03T11:22:54Z

@rfcbot merge

rfcbot · 2022-10-03T11:22:56Z

Team member @joshtriplett 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.

joshtriplett · 2022-10-03T11:23:10Z

cc @rust-lang/wg-const-eval; does this look reasonable to you?

RalfJung · 2022-10-03T18:29:17Z

library/core/src/ptr/non_null.rs

    #[must_use]
    #[inline]
    pub const unsafe fn as_ref<'a>(&self) -> &'a T {
        // SAFETY: the caller must guarantee that `self` meets all the
        // requirements for a reference.
-        unsafe { &*self.as_ptr() }
+        unsafe { &*self.as_ptr().cast_const() }


Why is the cast_const needed now?

Without the cast it will fail to compile with error[E0658]: dereferencing raw mutable pointers in constant functions is unstable (playground)

library/core/src/ptr/non_null.rs

rfcbot · 2022-10-04T14:51:21Z

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

rfcbot · 2022-10-14T14:52:47Z

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.

This will be merged soon.

archshift · 2023-05-22T18:02:38Z

Any updates here?

Amanieu · 2023-05-22T19:05:30Z

@bors r+

bors · 2023-05-22T19:05:33Z

📌 Commit e7047e6f79aaa492d2e13c553ca7a22fcdb682e7 has been approved by Amanieu

It is now in the queue for this repository.

bors · 2023-05-22T23:48:35Z

🔒 Merge conflict

This pull request and the master branch diverged in a way that cannot be automatically merged. Please rebase on top of the latest master branch, and let the reviewer approve again.

How do I rebase?

Assuming self is your fork and upstream is this repository, you can resolve the conflict following these steps:

git checkout nonnull_as_ref (switch to your branch)
git fetch upstream master (retrieve the latest master)
git rebase upstream/master -p (rebase on top of it)
Follow the on-screen instruction to resolve conflicts (check git status if you got lost).
git push self nonnull_as_ref --force-with-lease (update this PR)

You may also read Git Rebasing to Resolve Conflicts by Drew Blessing for a short tutorial.

Please avoid the "Resolve conflicts" button on GitHub. It uses git merge instead of git rebase which makes the PR commit history more difficult to read.

Sometimes step 4 will complete without asking for resolution. This is usually due to difference between how Cargo.lock conflict is handled during merge and rebase. This is normal, and you should still perform step 5 to update this PR.

Error message

CONFLICT (file location): src/test/ui/consts/const-eval/nonnull_as_ref_ub.stderr added in heads/homu-tmp inside a directory that was renamed in HEAD, suggesting it should perhaps be moved to tests/ui/const_prop/const-eval/nonnull_as_ref_ub.stderr.
CONFLICT (file location): src/test/ui/consts/const-eval/nonnull_as_ref_ub.rs added in heads/homu-tmp inside a directory that was renamed in HEAD, suggesting it should perhaps be moved to tests/ui/const_prop/const-eval/nonnull_as_ref_ub.rs.
CONFLICT (file location): src/test/ui/consts/const-eval/nonnull_as_ref.rs added in heads/homu-tmp inside a directory that was renamed in HEAD, suggesting it should perhaps be moved to tests/ui/const_prop/const-eval/nonnull_as_ref.rs.
Adding src/tools/rust-installer/test/image5/dir-to-install/foo
Adding src/tools/rust-installer/test/image4/dir-to-install/qux/bar
Adding src/tools/rust-installer/test/image4/baz
Adding src/tools/rust-installer/test/image3/bin/cargo
Adding src/tools/rust-installer/test/image2/something-to-install
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Adding src/tools/rust-installer/test/image1/something-to-not-install
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Adding src/tools/rust-installer/README.md
Adding src/tools/rust-installer/Cargo.toml
Adding src/tools/rust-installer/.gitignore
Auto-merging library/core/src/ptr/non_null.rs
warning: inexact rename detection was skipped due to too many files.
warning: you may want to set your merge.renamelimit variable to at least 27325 and retry the command.
Automatic merge failed; fix conflicts and then commit the result.

workingjubilee · 2023-07-30T12:53:55Z

@bors r=Amanieu

bors · 2023-07-30T12:53:56Z

📌 Commit 855b8b8 has been approved by Amanieu

It is now in the queue for this repository.

`const`-stablilize `NonNull::as_ref` A bunch of pointer to reference methods have been made unstably const some time ago in rust-lang#91823 under the feature gate `const_ptr_as_ref`. Out of these, `NonNull::as_ref` can be implemented as a `const fn` in stable rust today, so i hereby propose to const stabilize this function only. Tracking issue: rust-lang#91822 `@rustbot` label +T-libs-api -T-libs

…iaskrgr Rollup of 6 pull requests Successful merges: - rust-lang#98154 (merge functionality of `io::Sink` into `io::Empty`) - rust-lang#102198 (`const`-stablilize `NonNull::as_ref`) - rust-lang#114074 (inline format!() args from rustc_middle up to and including rustc_codegen_llvm (3)) - rust-lang#114246 (Weaken unnameable_types lint) - rust-lang#114256 (Fix invalid suggestion for mismatched types in closure arguments) - rust-lang#114258 (Simplify `Span::can_be_used_for_suggestions` a little tiny bit) r? `@ghost` `@rustbot` modify labels: rollup

rust-highfive assigned thomcc Sep 23, 2022

rustbot added T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. T-libs Relevant to the library team, which will review and decide on the PR/issue. labels Sep 23, 2022

rust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Sep 23, 2022

rustbot added the T-libs-api Relevant to the library API team, which will review and decide on the PR/issue. label Sep 23, 2022

rustbot removed the T-libs Relevant to the library team, which will review and decide on the PR/issue. label Sep 23, 2022

rust-highfive assigned joshtriplett and unassigned thomcc Sep 23, 2022

inquisitivecrystal added relnotes Marks issues that should be documented in the release notes of the next release. needs-fcp This change is insta-stable, so needs a completed FCP to proceed. labels Sep 24, 2022

joshtriplett removed the T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. label Oct 3, 2022

rfcbot added proposed-final-comment-period Proposed to merge/close by relevant subteam, see T-<team> label. Will enter FCP once signed off. disposition-merge This issue / PR is in PFCP or FCP with a disposition to merge it. labels Oct 3, 2022

RalfJung reviewed Oct 3, 2022

View reviewed changes

library/core/src/ptr/non_null.rs Show resolved Hide resolved

lukas-code force-pushed the nonnull_as_ref branch from 7fae23e to e7047e6 Compare October 4, 2022 09:35

fee1-dead approved these changes Oct 4, 2022

View reviewed changes

rfcbot added final-comment-period In the final comment period and will be merged soon unless new substantive objections are raised. and removed proposed-final-comment-period Proposed to merge/close by relevant subteam, see T-<team> label. Will enter FCP once signed off. labels Oct 4, 2022

apiraino removed the to-announce Announce this issue on triage meeting label Dec 8, 2022

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 May 22, 2023

bors 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 May 22, 2023

Lukas Markeffsky added 2 commits May 23, 2023 12:52

const stabilize NonNull::as_ref

3e07965

add tests for const NonNull::as_ref

855b8b8

lukas-code force-pushed the nonnull_as_ref branch from e7047e6 to 855b8b8 Compare May 23, 2023 14:22

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-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Jul 30, 2023

Dylan-DPC mentioned this pull request Jul 30, 2023

Rollup of 6 pull requests #114261

Closed

matthiaskrgr mentioned this pull request Jul 30, 2023

Rollup of 6 pull requests #114264

Merged

bors merged commit e3ca397 into rust-lang:master Jul 30, 2023

rustbot added this to the 1.73.0 milestone Jul 30, 2023

lukas-code deleted the nonnull_as_ref branch July 30, 2023 21:50

dtolnay mentioned this pull request Sep 9, 2024

Tracking Issue for const_ptr_as_ref #91822

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`const`-stablilize `NonNull::as_ref` #102198

`const`-stablilize `NonNull::as_ref` #102198

lukas-code commented Sep 23, 2022

rustbot commented Sep 23, 2022

rust-highfive commented Sep 23, 2022

thomcc commented Sep 23, 2022

joshtriplett commented Oct 3, 2022

rfcbot commented Oct 3, 2022 •

edited by Amanieu

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joshtriplett commented Oct 3, 2022

RalfJung Oct 3, 2022

lukas-code Oct 3, 2022

rfcbot commented Oct 4, 2022

rfcbot commented Oct 14, 2022

archshift commented May 22, 2023

Amanieu commented May 22, 2023

bors commented May 22, 2023

bors commented May 22, 2023

workingjubilee commented Jul 30, 2023

bors commented Jul 30, 2023

const-stablilize NonNull::as_ref #102198

const-stablilize NonNull::as_ref #102198

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lukas-code commented Sep 23, 2022

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workingjubilee commented Jul 30, 2023

bors commented Jul 30, 2023

`const`-stablilize `NonNull::as_ref` #102198

`const`-stablilize `NonNull::as_ref` #102198

rfcbot commented Oct 3, 2022 •

edited by Amanieu

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