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Make LocalWaker::new a const fn #53456

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Make LocalWaker::new a const fn #53456

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2 changes: 1 addition & 1 deletion src/libcore/task/wake.rs
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Expand Up @@ -119,7 +119,7 @@ impl LocalWaker {
/// For this function to be used safely, it must be sound to call `inner.wake_local()`
/// on the current thread.
#[inline]
pub unsafe fn new(inner: NonNull<dyn UnsafeWake>) -> Self {
pub const unsafe fn new(inner: NonNull<dyn UnsafeWake>) -> Self {
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Please add the rustc_const_unstable attribute and a test enabling the feature and using it.

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See #47562 for an example.

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Yep, I managed to get an example going. Unfortunately writing that example made me realise that this isn't usable for what I want anyway since it's !Send + !Sync so can't go in a static, as I don't know of any other usecases for this to be const I'm gonna close this and try to find an alternative.

One thing I noticed while adding the example, rustc_const_unstable requires a stable/unstable directly on the item being annotated, LocalWaker is in an unstable module so doesn't have a direct annotation, is there some reason the attribute needs to be directly on the item instead of inheriting from its parent scope?

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Is there some reason the attribute needs to be directly on the item instead of inheriting from its parent scope?

Does implementation lazyness count as a reason?

Most newly added const fns already had a stability attribute, so it was less hazzle to add an attribute to those that didn't have it than to correctly implement the attribute

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Implementation lazyness is the best reason.

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<Joke about Haskell has been elided due to laziness>

LocalWaker { inner }
}

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