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sync: Implement From<T> for OnceCell<T> #3877

merged 2 commits into from Jun 22, 2021


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@sb64 sb64 commented Jun 20, 2021


std::lazy::OnceCell implements From<T> for OnceCell<T>, but tokio::sync::OnceCell does not. Generally, tokio tries to match std's API as closely as possible, so this could be considered an API hole.


This PR adds that implementation. While this is a niche case, it also allows tokio::OnceCell to be constructed from a T. As it is right now, one can construct an uninitialized OnceCell with new and const_new, or one that may or may not be initialized using new_with, but it is not possible to construct one directly from a T (although this could be done with new_with(Some(T))).

@Darksonn Darksonn added A-tokio Area: The main tokio crate M-sync Module: tokio/sync labels Jun 21, 2021
@sb64 sb64 changed the title sync: Implement From for OnceCell sync: Implement From<T> for OnceCell<T> Jun 21, 2021
@Darksonn Darksonn merged commit 8456264 into tokio-rs:master Jun 22, 2021
@sb64 sb64 deleted the from-oncecell branch June 22, 2021 22:31
@Darksonn Darksonn mentioned this pull request Jul 2, 2021
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A-tokio Area: The main tokio crate M-sync Module: tokio/sync
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2 participants