Tracking Issue for `os_str_slice`

Feature gate: #![feature(os_str_slice)]

This is a tracking issue for an API for taking substrings of OsStr, which in combination with OsStr::as_encoded_bytes() would make it possible to implement most string operations in (portable) safe code.

Public API

impl OsStr {
    pub fn slice_encoded_bytes<R: ops::RangeBounds<usize>>(&self, range: R) -> &Self;
}

Steps / History

• ACP: https://github.com/rust-lang/libs-team/issues/306
• Implementation: #118484, #118569
• Final comment period (FCP)^1
• Stabilization PR

Unresolved Questions

• Currently this enforces the same requirements on all platforms, but on Unix (and some other platforms) the internal encoding of OsStr is already fully specified to be arbitrary bytes by means of the OsStrExt trait. Should we:
  • Relax the requirements on these platforms,
  • Keep enforcing the lowest common denominator invariants, or
  • Use strict checks now, but leave the possibility of relaxing them later?

Start with the Public API and review the ACP plus implementation references #118484 and #118569. Examine the unresolved platform-requirement questions, then follow the feature lifecycle for the pending FCP and stabilization PR; completion means the API is ready for stabilization.