This supercedes #74465 after a portion of once_cell was stabilized with #105587

Feature gate: #![feature(once_cell_try)]

This is a tracking issue for the *try* methods that go with the once_cell feature. Initially they were part of stabilization under once_cell (#105587) but was removed due to compatibility concerns with try trait v2 (#105587 (comment)).

Public API

impl<T> OnceCell<T> {
    pub fn get_or_try_init<F, E>(&self, f: F) -> Result<&T, E> where F: FnOnce() -> Result<T, E>;
}

impl<T> OnceLock<T> {
    pub fn get_or_try_init<F, E>(&self, f: F) -> Result<&T, E> where F: FnOnce() -> Result<T, E>;
}

Steps / History

• Original implementation: Add lazy initialization primitives to std #72414
• Try trait changes: Use Try trait to make Once[Cell | Lock]::get_or_try_init generic over return type #107122
• Final comment period (FCP)¹
• Stabilization PR

Unresolved Questions

• None yet.

cc @joboet @matklad just for reference