stabilize new RangeFrom type and iterator by pitaj · Pull Request #153380 · rust-lang/rust

pitaj · 2026-03-04T05:10:43Z

// in core and std
pub mod range;

// in core::range

pub struct RangeFrom<Idx> {
    pub start: Idx,
}

impl<Idx: fmt::Debug> fmt::Debug for RangeFrom<Idx> { /* ... */ }

impl<Idx: PartialOrd<Idx>> RangeFrom<Idx> {
    pub const fn contains<U>(&self, item: &U) -> bool
    where
        Idx: [const] PartialOrd<U>,
        U: ?Sized + [const] PartialOrd<Idx>;
}

impl<Idx: Step> RangeFrom<Idx> {
    pub fn iter(&self) -> RangeFromIter<Idx>;
}

impl<T> const RangeBounds<T> for RangeFrom<T> { /* ... */ }
impl<T> const RangeBounds<T> for RangeFrom<&T> { /* ... */ }

impl<T> const From<RangeFrom<T>> for legacy::RangeFrom<T> { /* ... */ }
impl<T> const From<legacy::RangeFrom<T>> for RangeFrom<T> { /* ... */ }

pub struct RangeFromIter<A>(/* ... */);

// `RangeFromIter::remainder` left unstable

impl<A: Step> Iterator for RangeFromIter<A> {
    type Item = A;
    /* ... */
}

impl<A: Step> FusedIterator for RangeFromIter<A> { }
impl<A: Step> IntoIterator for RangeFrom<A> {
    type Item = A;
    type IntoIter = RangeFromIter<A>;
    /* ... */
}

unsafe impl<T> const SliceIndex<[T]> for range::RangeFrom<usize> {
    type Output = [T];
    /* ... */
}
unsafe impl const SliceIndex<str> for range::RangeFrom<usize> {
    type Output = str;
    /* ... */
}

impl ops::Index<range::RangeFrom<usize>> for CStr {
    type Output = CStr;
    /* ... */
}

Tracking issue: #125687

r? tgross

tgross35 · 2026-03-04T05:28:20Z

library/core/src/range.rs

-/// *Note*: Overflow in the [`Iterator`] implementation (when the contained
+/// *Note*: Overflow in the [`IntoIterator`] implementation (when the contained
 /// data type reaches its numerical limit) is allowed to panic, wrap, or
 /// saturate. This behavior is defined by the implementation of the [`Step`]
 /// trait. For primitive integers, this follows the normal rules, and respects
-/// the overflow checks profile (panic in debug, wrap in release). Note also
-/// that overflow happens earlier than you might assume: the overflow happens
-/// in the call to `next` that yields the maximum value, as the range must be
-/// set to a state to yield the next value.
+/// the overflow checks profile (panic in debug, wrap in release). Unlike
+/// its legacy counterpart, the iterator will only panic after yielding the
+/// maximum value when overflow checks are enabled.


Do we have a test for this?

Yes: rangefrom-overflow-overflow-checks and friends

tgross35 · 2026-03-04T05:33:44Z

library/core/src/range/iter.rs

    /// Returns the remainder of the range being iterated over.
    #[inline]
    #[rustc_inherit_overflow_checks]
-    #[unstable(feature = "new_range_api", issue = "125687")]
+    #[stable(feature = "new_range_from_api", since = "CURRENT_RUSTC_VERSION")]
    pub fn remainder(self) -> RangeFrom<A> {


This could probably use an example

Added examples for RangeInclusive::remainder, RangeFrom::remainder, and Range::remainder

tgross35 · 2026-03-04T05:39:12Z

It doesn't look like RangeFromIter::remainder was listed on the tracking issue and that's new compared to the existing RangeFrom, so nominating for @rust-lang/libs-api. If you'd prefer to drop it here then I'm happy to approve.

@rustbot label +I-libs-api-nominated

The current RangeFrom has Index<RangeFrom<usize>> for ByteString and IndexMut<RangeFrom<usize>> for ByteString which should get added, those are unstable so it can happen here or later.

tgross35 · 2026-03-04T06:29:54Z

Noticing that RangeInclusiveIter::remainder is in the same boat, and is stable on nightly since #150522.

pitaj · 2026-03-07T19:42:39Z

remainder was in the original RFC: https://github.com/rust-lang/rfcs/blob/master/text/3550-new-range.md#iterator-types
So I don't think this need further discussion by T-libs-api?

tgross35 · 2026-03-08T09:09:34Z

remainder was in the original RFC: https://github.com/rust-lang/rfcs/blob/master/text/3550-new-range.md#iterator-types So I don't think this need further discussion by T-libs-api?

Accepted in an RFC doesn’t mean we don’t want to adjust or defer it at stabilization time. It’s probably fine here, but worth confirming since it wasn’t explicitly mentioned anywhere.

nia-e · 2026-03-10T16:13:41Z

This was discussed in today's @rust-lang/libs-api meeting and we approved the stabilization, including remainder. Thanks ^^

@rustbot label -I-libs-api-nominated

tgross35 · 2026-03-13T18:50:23Z

@rustbot author

Just needs a rebase

rustbot · 2026-03-13T18:50:28Z

Reminder, once the PR becomes ready for a review, use @rustbot ready.

tgross35

r=me after #154191 merges (I think there will be a small conflict)

View changes since this review

theemathas · 2026-03-23T03:12:26Z

I think the remainder method needs documentation saying that it can panic due to an overflow check? Or should it return Option?

rustbot · 2026-03-24T03:25:11Z

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.

pitaj · 2026-03-24T14:53:19Z

@bors r=tgross35

rust-bors · 2026-03-24T14:53:22Z

@pitaj: 🔑 Insufficient privileges: not in review users

pitaj · 2026-03-24T14:53:47Z

@rustbot ready

tgross35 · 2026-03-26T17:49:17Z

I think the remainder method needs documentation saying that it can panic due to an overflow check? Or should it return Option?

Seems worth checking, asked about this on Zulip #t-libs-api/api-changes > `RangeFrom::remainder` possible panic

nia-e · 2026-03-27T08:38:52Z

Seems like the Zulip thread brought up some previously unmentioned concerns, so renominating this. This is only about remainder, everything else should be fine still ^^

@rustbot label +I-libs-api-nominated

tgross35 · 2026-03-27T08:43:59Z

If you'd prefer to drop it here then I'm happy to approve.

Still applies, if you can drop remainder for now there's nothing stopping the rest from merging 🙂

pitaj · 2026-03-28T17:17:55Z

Removed remainder from the stabilization

stabilizes `core::range::RangeFrom` stabilizes `core::range::RangeFromIter` add examples for `remainder` method on range iterators `RangeFromIter::remainder` was not stabilized (see issue 154458)

tgross35 · 2026-03-28T19:37:52Z

@bors r+

rust-bors · 2026-03-28T19:37:55Z

📌 Commit 085dff4 has been approved by tgross35

It is now in the queue for this repository.

…, r=tgross35 stabilize new RangeFrom type and iterator ```rust // in core and std pub mod range; // in core::range pub struct RangeFrom<Idx> { pub start: Idx, } impl<Idx: fmt::Debug> fmt::Debug for RangeFrom<Idx> { /* ... */ } impl<Idx: PartialOrd<Idx>> RangeFrom<Idx> { pub const fn contains<U>(&self, item: &U) -> bool where Idx: [const] PartialOrd<U>, U: ?Sized + [const] PartialOrd<Idx>; } impl<Idx: Step> RangeFrom<Idx> { pub fn iter(&self) -> RangeFromIter<Idx>; } impl<T> const RangeBounds<T> for RangeFrom<T> { /* ... */ } impl<T> const RangeBounds<T> for RangeFrom<&T> { /* ... */ } impl<T> const From<RangeFrom<T>> for legacy::RangeFrom<T> { /* ... */ } impl<T> const From<legacy::RangeFrom<T>> for RangeFrom<T> { /* ... */ } pub struct RangeFromIter<A>(/* ... */); // `RangeFromIter::remainder` left unstable impl<A: Step> Iterator for RangeFromIter<A> { type Item = A; /* ... */ } impl<A: Step> FusedIterator for RangeFromIter<A> { } impl<A: Step> IntoIterator for RangeFrom<A> { type Item = A; type IntoIter = RangeFromIter<A>; /* ... */ } unsafe impl<T> const SliceIndex<[T]> for range::RangeFrom<usize> { type Output = [T]; /* ... */ } unsafe impl const SliceIndex<str> for range::RangeFrom<usize> { type Output = str; /* ... */ } impl ops::Index<range::RangeFrom<usize>> for CStr { type Output = CStr; /* ... */ } ``` Tracking issue: rust-lang#125687

…uwer Rollup of 9 pull requests Successful merges: - #150752 (Update libc to v0.2.183) - #153380 (stabilize new RangeFrom type and iterator) - #153834 (Merge `fabsf16/32/64/128` into `fabs::<F>`) - #154043 (simd_fmin/fmax: make semantics and name consistent with scalar intrinsics) - #154494 (triagebot: add reminder for bumping CI LLVM stamp) - #153374 (Fix LegacyKeyValueFormat report from docker build: dist-x86_64) - #154320 (`trim_prefix` for paths) - #154453 (Fix ice in rustdoc of private reexport) - #154515 (Notify stdarch maintainers on changes in std_detect)

Rollup of 9 pull requests Successful merges: - #153380 (stabilize new RangeFrom type and iterator) - #153834 (Merge `fabsf16/32/64/128` into `fabs::<F>`) - #154043 (simd_fmin/fmax: make semantics and name consistent with scalar intrinsics) - #154494 (triagebot: add reminder for bumping CI LLVM stamp) - #153374 (Fix LegacyKeyValueFormat report from docker build: dist-x86_64) - #154320 (`trim_prefix` for paths) - #154453 (Fix ice in rustdoc of private reexport) - #154504 (move many tests from `structs-enums` to `structs` or `enum`) - #154515 (Notify stdarch maintainers on changes in std_detect)

Rollup merge of #153380 - pitaj:stabilize-new_range_from_api, r=tgross35 stabilize new RangeFrom type and iterator ```rust // in core and std pub mod range; // in core::range pub struct RangeFrom<Idx> { pub start: Idx, } impl<Idx: fmt::Debug> fmt::Debug for RangeFrom<Idx> { /* ... */ } impl<Idx: PartialOrd<Idx>> RangeFrom<Idx> { pub const fn contains<U>(&self, item: &U) -> bool where Idx: [const] PartialOrd<U>, U: ?Sized + [const] PartialOrd<Idx>; } impl<Idx: Step> RangeFrom<Idx> { pub fn iter(&self) -> RangeFromIter<Idx>; } impl<T> const RangeBounds<T> for RangeFrom<T> { /* ... */ } impl<T> const RangeBounds<T> for RangeFrom<&T> { /* ... */ } impl<T> const From<RangeFrom<T>> for legacy::RangeFrom<T> { /* ... */ } impl<T> const From<legacy::RangeFrom<T>> for RangeFrom<T> { /* ... */ } pub struct RangeFromIter<A>(/* ... */); // `RangeFromIter::remainder` left unstable impl<A: Step> Iterator for RangeFromIter<A> { type Item = A; /* ... */ } impl<A: Step> FusedIterator for RangeFromIter<A> { } impl<A: Step> IntoIterator for RangeFrom<A> { type Item = A; type IntoIter = RangeFromIter<A>; /* ... */ } unsafe impl<T> const SliceIndex<[T]> for range::RangeFrom<usize> { type Output = [T]; /* ... */ } unsafe impl const SliceIndex<str> for range::RangeFrom<usize> { type Output = str; /* ... */ } impl ops::Index<range::RangeFrom<usize>> for CStr { type Output = CStr; /* ... */ } ``` Tracking issue: #125687

Rollup of 9 pull requests Successful merges: - rust-lang/rust#153380 (stabilize new RangeFrom type and iterator) - rust-lang/rust#153834 (Merge `fabsf16/32/64/128` into `fabs::<F>`) - rust-lang/rust#154043 (simd_fmin/fmax: make semantics and name consistent with scalar intrinsics) - rust-lang/rust#154494 (triagebot: add reminder for bumping CI LLVM stamp) - rust-lang/rust#153374 (Fix LegacyKeyValueFormat report from docker build: dist-x86_64) - rust-lang/rust#154320 (`trim_prefix` for paths) - rust-lang/rust#154453 (Fix ice in rustdoc of private reexport) - rust-lang/rust#154504 (move many tests from `structs-enums` to `structs` or `enum`) - rust-lang/rust#154515 (Notify stdarch maintainers on changes in std_detect)

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Tracking Issue for new_range_api (part of RFC 3550) #125687

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Tracking Issue for new_range_remainder #154458

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stabilize new RangeFrom type and iterator

085dff4

stabilizes `core::range::RangeFrom` stabilizes `core::range::RangeFromIter` add examples for `remainder` method on range iterators `RangeFromIter::remainder` was not stabilized (see issue 154458)

pitaj force-pushed the stabilize-new_range_from_api branch from 6209a93 to 085dff4 Compare March 28, 2026 18:00

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 Mar 28, 2026

JonathanBrouwer mentioned this pull request Mar 28, 2026

Rollup of 9 pull requests #154519

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GuillaumeGomez mentioned this pull request Mar 28, 2026

Rollup of 9 pull requests #154525

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rust-bors bot merged commit aad3710 into rust-lang:main Mar 29, 2026
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rustbot added this to the 1.96.0 milestone Mar 29, 2026

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