core/num: Implement feature `integer_cast_extras` by okaneco · Pull Request #154664 · rust-lang/rust

okaneco · 2026-04-01T05:52:02Z

Tracking issue #154650
Accepted ACP rust-lang/libs-team#765 (comment)

Implement saturating, checked, and strict casting between signed and unsigned integer primitives of the same bit-width.

Add cast_integer panic function to overflow_panic.rs

rustbot · 2026-04-01T05:52:08Z

r? @scottmcm

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rustbot · 2026-04-01T05:57:03Z

Some changes occurred in src/tools/cargo

cc @ehuss

rustbot · 2026-04-01T05:57:05Z

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.

okaneco · 2026-04-01T06:10:38Z

Sorry about that.
Messed up updating the branch commit in the rebase with a typo then had to fix the submodule changes. Think I got them all.

GrigorenkoPV · 2026-04-01T18:32:47Z

+        #[inline(always)]
+        pub const fn saturating_cast_signed(self) -> $SignedT {
+            // Clamp to the signed integer max size, which is ActualT::MAX >> 1.
+            if self < <$SignedT>::MAX.cast_unsigned() {


Suggested change

if self < <$SignedT>::MAX.cast_unsigned() {

if self < const { <$SignedT>::MAX.cast_unsigned() } {

Maybe? Not sure if it actually does something tho

It's #[inline(always)] and an as cast under the hood, I think we're okay without doing this.

GrigorenkoPV · 2026-04-01T18:35:52Z

+        #[must_use = "this returns the result of the operation, \
+                      without modifying the original"]
+        #[inline(always)]
+        pub const fn checked_cast_unsigned(self) -> Option<$UnsignedT> {


Should the docs maybe mentions that checked_cast_* do the same things as the existing TryFrom impls?

The recently added truncate/extend methods don't mention it on the checked_truncate method so I think we can omit it.

I don't think it's worth bringing up since they have different signatures, and the more relevant information is knowing what the integer min/max ranges are for the types involved. There are possible type inference issues that this function won't have either, along with being usable in const without const traits.

Sometimes I think that Rust docs over-explain or attempt to mention too many possible caveats which hinders readability, even though it's well-intentioned. This is one of the cases where it feels like extraneous information to me but I can see the other side too.

I think it's good to have simple cross-references between similar things. A little note here about "If you want to do this but to a generic target type, use TryFrom" or similar would be nice.

Implement saturating, checked, and strict casting between signed and unsigned integer primitives of the same bit-width. Add `cast_integer` function to `overflow_panic.rs`

scottmcm · 2026-04-20T02:19:32Z

Looks fine for unstable
@bors r+ rollup

rust-bors · 2026-04-20T02:19:34Z

📌 Commit fd3a74d has been approved by scottmcm

It is now in the queue for this repository.

…ttmcm core/num: Implement feature `integer_cast_extras` Tracking issue rust-lang#154650 Accepted ACP rust-lang/libs-team#765 (comment) Implement `saturating`, `checked`, and `strict` casting between signed and unsigned integer primitives of the same bit-width. Add `cast_integer` panic function to `overflow_panic.rs`

Rollup of 6 pull requests Successful merges: - #154654 (Move `std::io::ErrorKind` to `core::io`) - #155054 (constify `Index(Mut)`, `Deref(Mut)` for `Vec`) - #155507 (suggest expect instead of unwrap when arg provided) - #154664 (core/num: Implement feature `integer_cast_extras`) - #155474 (Rename incremental `cfail`/`cpass` revisions to `bfail`/`bpass`) - #155493 (docs(num): fix stale link to `mem::Alignment`)

…uwer Rollup of 10 pull requests Successful merges: - #155054 (constify `Index(Mut)`, `Deref(Mut)` for `Vec`) - #155264 (Add autocast support for `x86amx`) - #155507 (suggest expect instead of unwrap when arg provided) - #154664 (core/num: Implement feature `integer_cast_extras`) - #155238 (compiletest: add a new diff for compare-out-by-lines tests.) - #155474 (Rename incremental `cfail`/`cpass` revisions to `bfail`/`bpass`) - #155493 (docs(num): fix stale link to `mem::Alignment`) - #155529 (Remove `AttributeLintKind` variants - part 3) - #155531 (Tweak `is_ascii_punctuation()` docs wording) - #155533 (Provide a const new for `GlobalCache`)

Rollup merge of #154664 - okaneco:integer_cast_extras, r=scottmcm core/num: Implement feature `integer_cast_extras` Tracking issue #154650 Accepted ACP rust-lang/libs-team#765 (comment) Implement `saturating`, `checked`, and `strict` casting between signed and unsigned integer primitives of the same bit-width. Add `cast_integer` panic function to `overflow_panic.rs`

…uwer Rollup of 10 pull requests Successful merges: - rust-lang/rust#155054 (constify `Index(Mut)`, `Deref(Mut)` for `Vec`) - rust-lang/rust#155264 (Add autocast support for `x86amx`) - rust-lang/rust#155507 (suggest expect instead of unwrap when arg provided) - rust-lang/rust#154664 (core/num: Implement feature `integer_cast_extras`) - rust-lang/rust#155238 (compiletest: add a new diff for compare-out-by-lines tests.) - rust-lang/rust#155474 (Rename incremental `cfail`/`cpass` revisions to `bfail`/`bpass`) - rust-lang/rust#155493 (docs(num): fix stale link to `mem::Alignment`) - rust-lang/rust#155529 (Remove `AttributeLintKind` variants - part 3) - rust-lang/rust#155531 (Tweak `is_ascii_punctuation()` docs wording) - rust-lang/rust#155533 (Provide a const new for `GlobalCache`)

rustbot assigned scottmcm Apr 1, 2026

rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-libs Relevant to the library team, which will review and decide on the PR/issue. labels Apr 1, 2026

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okaneco mentioned this pull request Apr 1, 2026

Tracking Issue for integer_cast_extras #154650

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okaneco force-pushed the integer_cast_extras branch 2 times, most recently from 338f8fd to 391c4f0 Compare April 1, 2026 05:57

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okaneco force-pushed the integer_cast_extras branch 2 times, most recently from 37c9674 to 7408601 Compare April 1, 2026 06:09

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okaneco force-pushed the integer_cast_extras branch from 7408601 to e88d2eb Compare April 1, 2026 06:19

GrigorenkoPV reviewed Apr 1, 2026

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Comment thread library/core/src/num/int_macros.rs Outdated

GrigorenkoPV reviewed Apr 1, 2026

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core/num: Implement feature integer_cast_extras

fd3a74d

Implement saturating, checked, and strict casting between signed and unsigned integer primitives of the same bit-width. Add `cast_integer` function to `overflow_panic.rs`

okaneco force-pushed the integer_cast_extras branch from e88d2eb to fd3a74d Compare April 1, 2026 19:59

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 Apr 20, 2026

jhpratt mentioned this pull request Apr 20, 2026

Rollup of 6 pull requests #155534

Closed

JonathanBrouwer mentioned this pull request Apr 20, 2026

Rollup of 10 pull requests #155542

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rust-bors Bot merged commit 26f47ae into rust-lang:main Apr 20, 2026
11 checks passed

rustbot added this to the 1.97.0 milestone Apr 20, 2026

okaneco deleted the integer_cast_extras branch April 20, 2026 18:30

	if self < <$SignedT>::MAX.cast_unsigned() {
	if self < const { <$SignedT>::MAX.cast_unsigned() } {

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