constify from_fn, try_from_fn, try_map, map by bend-n · Pull Request #147071 · rust-lang/rust

bend-n · 2025-09-26T15:29:55Z

adds the const_array feature
reimplements try_map in more or less the same way

rustbot · 2025-09-26T18:44:29Z

rustbot has assigned @ibraheemdev.
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library/core/src/array/drain.rs

oli-obk · 2025-10-11T10:19:56Z

library/core/src/array/mod.rs

+            else {
+                // SAFETY: this slice will contain only initialized objects.
+                unsafe {
+                    x.array_mut.get_unchecked_mut(..x.initialized).assume_init_drop();


What part of this isn't const evaluable? The get_unchecked_mut?

assume_init_drop, and changing it to be const had some rammifications for some reason, causing some tests to fail. #147071 (comment)

Looks like just trivial stderr file changes. Feel free to just bless them.

But is that code path testable in const? Since it's only happening in a panic path, I think it's unreachable anyway in const contexts. They never unwind and never will unwind. So maybe just document that and move the entire drop method body into the non-const code path... Or can we keep it non-const and avoid any drop happening for it by "disarming it" in the success path?

its used in try_from_fn, so it can get dropped in const context?

Ah right. Hmm. Wondering how to write an observable test for this. I think if you use a type with a reference to a Cell and in its const drop impl increment that cell, you should see in a const context that the cell isn't incremented if try_map errors/returns None.

Ah oops, wanted to write this test but forgot about it when I was on a computer.

Need to reinvestigate this to get it all back into cache.

It oughtnt really be needed now, as the behaviour is identical to the non const version?

library/core/src/array/mod.rs

library/core/src/ops/try_trait.rs

rustbot · 2025-10-11T11:16:46Z

The Miri subtree was changed

cc @rust-lang/miri

library/core/src/array/drain.rs

bend-n · 2025-10-11T12:05:39Z

library/core/src/array/drain.rs

+where
+    F: [const] FnMut(T) -> U,
+{
+    extern "rust-call" fn call_mut(&mut self, (i,): (usize,)) -> Self::Output {


it would be possible to ignore this i and just use moved, but, uh, i think that would be somewhat confusing.

rustbot · 2025-11-26T21:32:27Z

Some changes occurred in src/tools/cargo

cc @ehuss

oli-obk

just a rebase fragemtn and a nit

View changes since this review

src/tools/cargo

library/core/src/array/drain.rs

rustbot · 2025-11-27T13:16:56Z

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 · 2025-11-27T16:17:36Z

@bors r+

bors · 2025-11-27T16:17:38Z

📌 Commit e3a2c23 has been approved by oli-obk

It is now in the queue for this repository.

Rollup of 8 pull requests Successful merges: - #147071 (constify from_fn, try_from_fn, try_map, map) - #148930 (tweak editor configs) - #149320 (-Znext-solver: normalize expected function input types when fudging) - #149363 (Port the `#![windows_subsystem]` attribute to the new attribute system) - #149378 (make run-make tests use 2024 edition by default) - #149381 (Add `impl TrustedLen` on `BTree{Map,Set}` iterators) - #149388 (remove session+blob decoder construction) - #149390 (`rust-analyzer` subtree update) r? `@ghost` `@rustbot` modify labels: rollup

Rollup merge of #147071 - bend-n:const_array-ops, r=oli-obk constify from_fn, try_from_fn, try_map, map adds the `const_array` feature reimplements `try_map` in more or less the same way

Rollup of 8 pull requests Successful merges: - rust-lang/rust#147071 (constify from_fn, try_from_fn, try_map, map) - rust-lang/rust#148930 (tweak editor configs) - rust-lang/rust#149320 (-Znext-solver: normalize expected function input types when fudging) - rust-lang/rust#149363 (Port the `#![windows_subsystem]` attribute to the new attribute system) - rust-lang/rust#149378 (make run-make tests use 2024 edition by default) - rust-lang/rust#149381 (Add `impl TrustedLen` on `BTree{Map,Set}` iterators) - rust-lang/rust#149388 (remove session+blob decoder construction) - rust-lang/rust#149390 (`rust-analyzer` subtree update) r? `@ghost` `@rustbot` modify labels: rollup

…iaskrgr Rollup of 8 pull requests Successful merges: - rust-lang#147071 (constify from_fn, try_from_fn, try_map, map) - rust-lang#148930 (tweak editor configs) - rust-lang#149320 (-Znext-solver: normalize expected function input types when fudging) - rust-lang#149363 (Port the `#![windows_subsystem]` attribute to the new attribute system) - rust-lang#149378 (make run-make tests use 2024 edition by default) - rust-lang#149381 (Add `impl TrustedLen` on `BTree{Map,Set}` iterators) - rust-lang#149388 (remove session+blob decoder construction) - rust-lang#149390 (`rust-analyzer` subtree update) r? `@ghost` `@rustbot` modify labels: rollup

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bend-n marked this pull request as ready for review September 26, 2025 18:44

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Tracking Issue for const_array #147606

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bend-n requested a review from oli-obk November 27, 2025 04:28

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tests/rustdoc-gui/setting-auto-hide-item-methods-docs.goml timed out #146587

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bend-n added 2 commits November 27, 2025 20:16

tests

eddf2f8

constify from_fn, try_from_fn, try_map, map

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bend-n force-pushed the const_array-ops branch from ebc402b to 4c15a50 Compare November 27, 2025 13:16

redo the drain

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bend-n force-pushed the const_array-ops branch from 4c15a50 to e3a2c23 Compare November 27, 2025 13:18

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 Nov 27, 2025

matthiaskrgr mentioned this pull request Nov 27, 2025

Rollup of 8 pull requests #149397

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bors merged commit b1b3e5e into rust-lang:main Nov 27, 2025
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rustbot added this to the 1.93.0 milestone Nov 27, 2025

bend-n deleted the const_array-ops branch November 28, 2025 04:34

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