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Tracking Issue for const_collections_with_hasher #102575

Closed
#133696
Closed
Tracking Issue for const_collections_with_hasher#102575
#133696
Labels
C-tracking-issueCategory: An issue tracking the progress of sth. like the implementation of an RFCT-libs-api[DEPRECATED; DO NOT USE]disposition-mergeThis issue / PR is in PFCP or FCP with a disposition to merge it.finished-final-comment-periodThe final comment period is finished for this PR / Issue.
Milestone
1.85.0

Description

@aDotInTheVoid
aDotInTheVoid
opened on Oct 2, 2022

Feature gate: #![feature(const_collections_with_hasher)]

This is a tracking issue for making HashMap::with_hasher and HashSet::with_hasher const.

Public API

// std::collections
impl<K, V, S> HashMap<K, V, S> {
    pub const fn with_hasher(hash_builder: S) -> HashMap<K, V, S> { ... }
}

impl<T, S> HashSet<T, S> {
    pub const fn with_hasher(hasher: S) -> HashSet<T, S> { ... }
}

Steps / History

Unresolved Questions

  • None yet.

Footnotes

  1. https://std-dev-guide.rust-lang.org/feature-lifecycle/stabilization.html ↩

Activity

  1. aDotInTheVoid
    added
    C-tracking-issueCategory: An issue tracking the progress of sth. like the implementation of an RFC
    T-libs-api[DEPRECATED; DO NOT USE]
    on Oct 2, 2022
  2. notriddle
    added a commit that references this issue on Oct 5, 2022

    Rollup merge of rust-lang#102574 - aDotInTheVoid:const_collections_wi…

    4025e95

  3. GoldsteinE commented on Jan 3, 2023

    @GoldsteinE
    GoldsteinE
    on Jan 3, 2023
    Contributor

    What blocks this from stabilization? Can I do something to move it forward?

  4. aDotInTheVoid commented on Jan 5, 2023

    @aDotInTheVoid
    aDotInTheVoid
    on Jan 5, 2023
    MemberAuthor

    @GoldsteinE: see https://std-dev-guide.rust-lang.org/feature-lifecycle/stabilization.html

    Main questions for stabilization are do we want to add the constraint that an empty hashmap can be const constructed (ie doesn't alloc and more). This is true for the current hashbrown design, but might not be true for other alternatives. I'm not framiliar enough with hashmap design to say.

  5. Amanieu commented on Aug 3, 2023

    @Amanieu
    Amanieu
    on Aug 3, 2023
    Member

    This is fairly straightforward, we are essentially guaranteeing that a newly created HashMap does not allocate any memory.

    @rfcbot fcp merge

  6. rfcbot commented on Aug 3, 2023

    @rfcbot
    rfcbot
    on Aug 3, 2023

    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.

  7. rfcbot
    added
    proposed-final-comment-periodProposed to merge/close by relevant subteam, see T-<team> label. Will enter FCP once signed off.
    disposition-mergeThis issue / PR is in PFCP or FCP with a disposition to merge it.
    final-comment-periodIn the final comment period and will be merged soon unless new substantive objections are raised.
    and removed
    proposed-final-comment-periodProposed to merge/close by relevant subteam, see T-<team> label. Will enter FCP once signed off.
    on Aug 3, 2023

  8. rfcbot commented on Aug 3, 2023

    @rfcbot
    rfcbot
    on Aug 3, 2023

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

  9. rfcbot
    added
    finished-final-comment-periodThe final comment period is finished for this PR / Issue.
    to-announceAnnounce this issue on triage meeting
    and removed
    final-comment-periodIn the final comment period and will be merged soon unless new substantive objections are raised.
    on Aug 13, 2023

  10. 15 remaining items

  11. matthiaskrgr
    added 2 commits that reference this issue on Nov 3, 2024

    Rollup merge of rust-lang#132503 - RalfJung:const-hash-map, r=Amanieu

    74d2561

    Rollup merge of rust-lang#132503 - RalfJung:const-hash-map, r=Amanieu

    e937938
  12. rust-timer
    added a commit that references this issue on Nov 3, 2024

    Unrolled build for rust-lang#132503

    8498263

  13. RalfJung commented on Nov 3, 2024

    @RalfJung
    RalfJung
    on Nov 3, 2024
    Member

    The PR that should enable us to safely expose const fn from hashbrown is up now: #132541.

    (That's just the infrastructure for this, once it lands, a bit of wiring-up needs to happen in hashbrown.)

  14. RalfJung commented on Nov 12, 2024

    @RalfJung
    RalfJung
    on Nov 12, 2024
    Member

    Cc @rust-lang/wg-const-eval

  15. RalfJung
    added 2 commits that reference this issue on Nov 30, 2024

    Rollup merge of rust-lang#133670 - RalfJung:hashbrown, r=Amanieu

    61adb5b

    Rollup merge of rust-lang#133670 - RalfJung:hashbrown, r=Amanieu

    ec000a7
  16. rust-timer
    added a commit that references this issue on Nov 30, 2024

    Unrolled build for rust-lang#133670

    fea754b
  17. matthiaskrgr
    added a commit that references this issue on Dec 3, 2024

    Rollup merge of rust-lang#133696 - RalfJung:const-hashmap, r=cuviper

    1ae6f47
  18. bors
    closed this as completedin 1ae6f47on Dec 3, 2024
  19. rust-timer
    added a commit that references this issue on Dec 3, 2024

    Unrolled build for rust-lang#133696

    3b4899d
  20. github-actions
    added a commit that references this issue on Dec 4, 2024

    Rollup merge of #133696 - RalfJung:const-hashmap, r=cuviper

    ae143c6
  21. Mark-Simulacrum
    added this to the 1.85.0 milestone on Jan 20, 2025
  22. github-actions
    added 2 commits that reference this issue on Mar 11, 2025

    Rollup merge of rust-lang#133670 - RalfJung:hashbrown, r=Amanieu

    8a196a3

    Rollup merge of rust-lang#133696 - RalfJung:const-hashmap, r=cuviper

    d3f38c5
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    C-tracking-issueCategory: An issue tracking the progress of sth. like the implementation of an RFCT-libs-api[DEPRECATED; DO NOT USE]disposition-mergeThis issue / PR is in PFCP or FCP with a disposition to merge it.finished-final-comment-periodThe final comment period is finished for this PR / Issue.

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