Revert const hacks and use const closures in std by oli-obk · Pull Request #155957 · rust-lang/rust

oli-obk · 2026-04-29T07:11:42Z

This revealed some smaller bugs in stability checking that I fixed where needed:

const closures use the const stability of their parent
trait method default bodies use the const stability of their trait

Otherwise trivial reverts of the const hacks that were added

rustbot · 2026-04-29T07:11:47Z

rustbot has assigned @jhpratt.
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jhpratt

r=me from a libs side with the one question resolved. I'm not a compiler reviewer, but the small change is obviously correct.

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theemathas · 2026-04-29T07:59:37Z

Does this fix #155781?

jhpratt · 2026-04-29T08:10:57Z

I'm pretty sure it will

oli-obk · 2026-04-29T15:35:54Z

    F: [const] FnMut(usize) -> T + [const] Destruct,
 {
-    try_from_fn(NeverShortCircuit::wrap_mut_1(f)).0
+    try_from_fn(const move |a| NeverShortCircuit(f(a))).0


Yea, the Wrapped type was only used in these two cases

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bend-n · 2026-04-29T16:18:51Z

    debug_assert!(elem_layout.size() == elem_layout.pad_to_align().size());

-    // FIXME(const-hack) return to using `map` and `map_err` once `const_closures` is implemented
-    match elem_layout.repeat_packed(cap) {


why isn't it repeat_packed?

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I think this was a very recent change and I messed up a rebase over it, fixed

oli-obk · 2026-04-29T16:26:44Z

Does this fix #155781?

oh. yes! I ran into this issue but didn't realize there was an issue open for it

rustbot · 2026-05-03T09:17:22Z

This PR was rebased onto a different main commit. Here's a range-diff highlighting what actually changed.

Rebasing is a normal part of keeping PRs up to date, so no action is needed—this note is just to help reviewers.

oli-obk · 2026-05-03T09:17:38Z

@bors r=jhpratt

rust-bors · 2026-05-03T09:17:41Z

📌 Commit c9725eb has been approved by jhpratt

It is now in the queue for this repository.

oli-obk · 2026-05-03T09:17:45Z

@bors rollup

Revert const hacks and use const closures in std This revealed some smaller bugs in stability checking that I fixed where needed: * const closures use the const stability of their parent * trait method default bodies use the const stability of their trait Otherwise trivial reverts of the const hacks that were added fixes rust-lang#155781

…uwer Rollup of 3 pull requests Successful merges: - #156073 ([rustdoc] Fix `doc_cfg` feature on reexports) - #155433 (Rip out rustc_layout_scalar_valid_range_* attribute support) - #155957 (Revert const hacks and use const closures in std)

JonathanBrouwer · 2026-05-03T14:32:41Z

@bors r-
#156108 (comment)

Not sure how this PR causes it, but the other 2 PRs in the rollup seem even less likely
@bors try jobs=dist-i586-gnu-i586-i686-musl

rust-bors · 2026-05-03T14:32:46Z

This pull request was unapproved.

This PR was contained in a rollup (#156108), which was unapproved.

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Revert const hacks and use const closures in std try-job: dist-i586-gnu-i586-i686-musl

JonathanBrouwer · 2026-05-03T14:34:56Z

    {
-        // FIXME(const-hack): revert this to a const closure
-        #[rustc_const_unstable(feature = "const_iter", issue = "92476")]
-        #[rustc_inherit_overflow_checks]


Right probably caused by the removal of rustc_inherit_overflow_checks

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rust-bors · 2026-05-03T15:28:06Z

💔 Test for 6389d03 failed: CI. Failed job:

try - dist-i586-gnu-i586-i686-musl (web logs, enhanced plaintext logs)

rust-log-analyzer · 2026-05-03T15:28:09Z

The job dist-i586-gnu-i586-i686-musl failed! Check out the build log: (web) (plain enhanced) (plain)

Click to see the possible cause of the failure (guessed by this bot)

failures:

---- [ui] tests/ui/iterators/iter-count-overflow-debug.rs stdout ----

error: test did not exit with success! code=Some(101) so test would pass with `run-fail`
status: exit status: 101
command: cd "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/iterators/iter-count-overflow-debug" && RUSTC="/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/bin/rustc" RUST_TEST_THREADS="4" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/iterators/iter-count-overflow-debug/a"
stdout: none
--- stderr -------------------------------

rustbot assigned jhpratt Apr 29, 2026

rustbot 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. T-libs Relevant to the library team, which will review and decide on the PR/issue. labels Apr 29, 2026

jhpratt reviewed Apr 29, 2026

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Comment thread library/core/src/ops/try_trait.rs

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fmease added the PG-const-traits Project group: Const traits label Apr 29, 2026

ChrisDenton mentioned this pull request Apr 29, 2026

Libs proposal: Policy for constifying traits and trait implementations #155816

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oli-obk commented Apr 29, 2026

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bend-n reviewed Apr 29, 2026

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oli-obk force-pushed the const-closure-std branch 2 times, most recently from 9b213cb to 3b0794b Compare April 29, 2026 16:25

oli-obk added 2 commits May 3, 2026 11:15

Remove const closure hacks in libstd

33a54dd

Revert const hack and use const closure

c9725eb

oli-obk force-pushed the const-closure-std branch from 3b0794b to c9725eb Compare May 3, 2026 09:17

rust-bors Bot 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 3, 2026

JonathanBrouwer mentioned this pull request May 3, 2026

Rollup of 3 pull requests #156108

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rust-bors Bot added the S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. label May 3, 2026

rust-bors Bot removed the S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. label May 3, 2026

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rust-bors Bot pushed a commit that referenced this pull request May 3, 2026

Auto merge of #155957 - oli-obk:const-closure-std, r=<try>

6389d03

Revert const hacks and use const closures in std try-job: dist-i586-gnu-i586-i686-musl

JonathanBrouwer reviewed May 3, 2026

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