In Option::get_or_insert_with(), forget the None instead of dropping it.
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…ing it. This allows eliminating the `T: [const] Destruct` bounds and avoids generating an implicit `drop_in_place::<Option<T>>()` that will never do anything. Ideally, the compiler would prove that that drop is not necessary itself, but it currently doesn't, even with `const_precise_live_drops` enabled.
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r? @ibraheemdev rustbot has assigned @ibraheemdev. Use |
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cc @cyb0124 (this change is based on their idea) |
hkBst
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Nov 6, 2025
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| /// Test that `Option::get_or_insert_*` are usable in const contexts, including with types that | ||
| /// do not have `const Drop` (except for [`Option::get_or_insert()`], which is not const). | ||
| #[test] | ||
| fn option_const_get_or_insert() { |
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Maybe split this test such that we can use a more unambiguous name don't have to mention an exception.
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| // It could also be expressed as `core::ptr::write(self, Some(f()))`; that would be | ||
| // additional unsafe code, so should be avoided unless a reason is found. |
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maybe include the unsafe block inside the code example?
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Per #148486 (comment)
In
Option::get_or_insert_with(), after replacing theNonewithSome, forget theNoneinstead of dropping it.This allows eliminating the
T: [const] Destructbounds, making the functions more flexible in (unstable) const contexts, and avoids generating an implicitdrop_in_place::<Option<T>>()that will never do anything (and which might even persist after optimization).