Feature gate: #![feature(round_char_boundary)]

This is a tracking issue for str::{floor, ceil}_char_boundary.

Public API

impl str {
    // Returns the character boundary at or immediately before `index`
    const fn floor_char_boundary(&self, index: usize) -> usize;
    // Returns the character boundary at or immediately after `index`
    const fn ceil_char_boundary(&self, index: usize) -> usize;
}

Steps / History

• Implementation: Add {floor,ceil}_char_boundary methods to str #86497
  • Don't panic in ceil_char_boundary: Don't panic in ceil_char_boundary #112387
  • Made const: str: Mark unstable round_char_boundary feature functions as const #144472
• Final comment period (FCP)
• Stabilization PR

Unresolved Questions

• Should ceil_char_boundary panic when indices are out of bounds? Don't panic in ceil_char_boundary #112387 updated this to return len instead.