feat: implement OnceLock#519
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- ensure failed init does not mark `DONE_BIT` - align behavior with std OnceLock semantics - improve test coverage - add docs and comments
chise0713
commented
Apr 15, 2026
| fn call_once_slow( | ||
| &self, | ||
| ignore_poison: bool, | ||
| from_once_lock: bool, // work around for `OnceLock::get_or_try_init` |
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To fix incorrect Err handling in OnceLock::get_or_try_init
and align with std semantics, I extended Once's internal API
to allow manual control over its state.
This keeps the public API unchanged, but adds a OnceLock-specific
code path internally.
I'm not entirely confident this is the best approach, so I'd really
appreciate any feedback!
chise0713
commented
Apr 15, 2026
| value: UnsafeCell<MaybeUninit<T>>, | ||
| } | ||
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| impl<T> OnceLock<T> { |
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The documentation is mostly adapted from the standard library.
- eliminate invalid state combinations - improve readability and intent clarity
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This PR is based on the
OnceLockimplementation from the standard library, with modifications to adapt it to ourOnceimplementation.Related: #440
Tests may benefit from further validation and edge case coverage.
Any feedback on the design and implementation would be appreciated.