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Description
Feature gate: #![feature(const_convert)]
This is a tracking issue for constifying some conversions (see #87852 for numeric conversions). Among other things this enables using the ?-operator on Option and Result in const contexts for trivial conversions. Note that this does not add any new implementations, it only constifies the existing ones.
Simple example:
const fn foo() -> Result<(), FooError> {
let bar = try_thing()?; // A function that returns Result<_, FooError>
do_stuff_with(bar)?; // A function that returns Result<_, FooError>
Ok(())
}Public API
Constifies the following impls
impl<T, U> const Into<U> for T where U: ~const From<T>;
impl<T> const From<T> for T;
impl<T> const ops::Try for Option<T>;
impl<T> const ops::FromResidual for Option<T>;
impl<T, E> const ops::Try for Result<T, E>;
impl<T, E, F> const ops::FromResidual<Result<convert::Infallible, E>> for Result<T, F> where F: ~const From<E>;
impl<T: ?Sized, U: ?Sized> const AsRef<U> for &T where T: ~const AsRef<U>;
impl<T: ?Sized, U: ?Sized> const AsRef<U> for &mut T where T: ~const AsRef<U>;
impl<T: ?Sized, U: ?Sized> const AsMut<U> for &mut T where T: ~const AsMut<U>;
impl<T, U> const TryInto<U> for T where U: ~const TryFrom<T>;
impl<T, U> const TryFrom<U> for T where U: ~const Into<T>;Steps / History
- Implementation: Constify ?-operator for Result and Option #86853
- More impls Extend const_convert to rest of blanket core::convert impls #92382
- Blocked on Deprecated tracking issue for closed RFC 2632,
impl const Trait for Tyand~const(tilde const) syntax (const_trait_impl) #67792 and Tracking Issue fortry_trait_v2, A new design for the?desugaring (RFC#3058) #84277 - Final comment period (FCP)
- Stabilization PR
Unresolved Questions
- None yet.
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Category: An issue tracking the progress of sth. like the implementation of an RFCCategory: An issue tracking the progress of sth. like the implementation of an RFC`#![feature(const_trait_impl)]``#![feature(const_trait_impl)]`Relevant to the library API team, which will review and decide on the PR/issue.Relevant to the library API team, which will review and decide on the PR/issue.