Tracking Issue for titlecase handling in core::char

Feature gate: #![feature(titlecase)]

This is a tracking issue for library functions to handle title-casing of Unicode characters.

Public API

// core

impl char {
    pub fn is_cased(self) -> bool;
    pub fn case(self) -> Option<CharCase>;
    pub fn is_titlecase(self) -> bool;
    pub fn to_titlecase(self) -> ToTitlecase;
}

mod char {
    #[derive(Clone, Copy, Debug, PartialEq, Eq, Hash, PartialOrd, Ord)]
    pub enum CharCase {
        Lower = 0b00,
        Title = 0b10,
        Upper = 0b11,
    }

    struct ToTitlecase { ... }
    impl Iterator for ToTitlecase { ... }
    impl DoubleEndedIterator for ToTitlecase { ... }
    impl FusedIterator for ToTitlecase { }
    impl ExactSizeIterator for ToTitlecase { ... }
    impl fmt::Display for ToTitlecase { ... }
}

// alloc

impl str {
    fn word_to_titlecase(&self) -> String;
}

Steps / History

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

ACP: Add titlecase APIs to char libs-team#354
Implementation: Add APIs for dealing with titlecase #122668 Fix typo in doc comment for char::to_titlecase #154288 Add str::word_to_titlecase() to alloc #155705
Final comment period (FCP)¹
Stabilization PR

Unresolved Questions

None yet.

https://std-dev-guide.rust-lang.org/feature-lifecycle/stabilization.html ↩

Rollup merge of rust-lang#122668 - Jules-Bertholet:titlecase, r=Mark-…

Auto merge of #122668 - Jules-Bertholet:titlecase, r=Mark-Simulacrum

Rollup merge of rust-lang#122668 - Jules-Bertholet:titlecase, r=Mark-…

@rustbot

@rustbot label -S-tracking-unimplemented S-tracking-needs-to-bake

Rollup merge of rust-lang#155469 - Jules-Bertholet:titlecase-idents, …

Unrolled build for #155469

Rollup merge of rust-lang#155705 - Jules-Bertholet:word-to-titlecase,…

Unrolled build for #155705

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Tracking Issue for titlecase handling in `core::char` #153892

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Tracking Issue for titlecase handling in core::char #153892

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Jules-Bertholet commented on Mar 24, 2026

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Tracking Issue for titlecase handling in `core::char` #153892