Tracking Issue for `str::replace_with`

Feature gate: #![feature(replace_with)]

This is a tracking issue for the implementation of replace_with and replacen_with for the String type in standart library, followed from the ACP (https://github.com/rust-lang/libs-team/issues/344#issuecomment-3404030290).

This feature adds str::replace_with as an augmentation of str::replace and str::replacen_with as an augmentation of str:replacen to the standard library. Compared to the current versions, these functions allow for passing an f: impl FnMut(&str) -> S that can be used to produce replacements dynamically as well as to insert custom computations such as counting the number of changes.

Public API

// str::replace_with

fn replace_with<P: Pattern, S: AsRef<str>>(
    &self,
    from: P,
    f: impl FnMut(&str) -> S,
) -> String;

// str::replacen_with

fn replacen_with<P: Pattern, S: AsRef<str>>(
    &self,
    from: P,
    f: impl FnMut(&str) -> S,
    count: usize
) -> String;

Steps / History

(Remember to update the S-tracking-* label when checking boxes.)

• ACP: rust-lang/libs-team#344
• Implementation: https://github.com/rust-lang/rust/pull/147741
• Final comment period (FCP)^1
• Stabilization PR

Unresolved Questions

• None yet.

Read the proposed str::replace_with and str::replacen_with signatures, then review the linked implementation PR rust-lang/rust#147741 and the ACP discussion. The remaining tracking steps are the final comment period and a stabilization PR; done means those lifecycle steps have been completed.