Feature gate: #![feature(split_at_checked)].

This is a tracking issue for the addition of split_at_checked and split_at_mut_checked methods to [T] and str types which are non-panicking versions of split_at and split_at_mut methods. Rather than panicking when spit index is out of range (like split_at does), the methods return None.

Public API

impl<T> [T] {
    pub fn split_at_checked(&self, mid: usize) -> Option<(&[T], &[T])>;
    pub fn split_at_mut_checked(&self, mid: usize) -> Option<(&[T], &[T])>;
}

impl str {
    pub fn split_at_checked(&self, mid: usize) -> Option<(&str, &str)>;
    pub fn split_at_mut_checked(&mut self, mid: usize) -> Option<(&str, &str)>;
}

Steps / History

• ACP: ACP: Introduce checked_split_at{,_mut} methods libs-team#308
• Implementation: core: introduce split_at{,_mut}_checked #118578
• Final comment period (FCP)¹
• Stabilization PR

Unresolved Questions

Name of the methods. Some possibilities (suggested in ACP discussion):

1. split_at_checked and split_at_mut_checked — follows naming of split_at_unchecked and split_at_mut_unchecked. Using suffix makes the names sort nicely together.
2. checked_split_at and checked_split_at_mut — follows naming convention of arithmetic types (e.g. checked_add). Those new functions serve similar purpose as checked arithmetic operations.
3. try_split_at and try_split_at_mut — follows naming of various fallible methods such as try_from, try_new, try_for_each etc. Shortest of the three suggestions.