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Rollup merge of #89509 - jhpratt:stabilize-const_unreachable_unchecked, r=oli-obk

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Stabilize `unreachable_unchecked` as `const fn`

Closes #53188

This PR stabilizes `core::hint::unreachable_unchecked` as `const fn`. MIRI is able to detect when this method is called. Stabilization was delayed until `const_panic` was stabilized so as to avoid users calling this method in its place (thus resulting in runtime UB). With #89508, that is no longer an issue.

````@rustbot```` label +A-const-eval +A-const-fn +T-lang +S-blocked

(not sure why it's T-lang, but that's what the tracking issue is)
This commit is contained in:
Matthias Krüger 2021-10-16 08:02:20 +02:00 • committed by GitHub
commit 9ae0804859
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6 changed files with 7 additions and 11 deletions
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2
library/core/src/hint.rs
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@ -44,7 +44,7 @@ use crate::intrinsics;
/// ```
#[inline]
#[stable(feature = "unreachable", since = "1.27.0")]
#[rustc_const_unstable(feature = "const_unreachable_unchecked", issue = "53188")]
#[rustc_const_stable(feature = "const_unreachable_unchecked", since = "1.57.0")]
pub const unsafe fn unreachable_unchecked() -> ! {
// SAFETY: the safety contract for `intrinsics::unreachable` must
// be upheld by the caller.

2
library/core/src/intrinsics.rs
View file

@ -735,7 +735,7 @@ extern "rust-intrinsic" {
/// reach code marked with this function.
///
/// The stabilized version of this intrinsic is [`core::hint::unreachable_unchecked`].
#[rustc_const_unstable(feature = "const_unreachable_unchecked", issue = "53188")]
#[rustc_const_stable(feature = "const_unreachable_unchecked", since = "1.57.0")]
pub fn unreachable() -> !;
/// Informs the optimizer that a condition is always true.

1
library/core/src/lib.rs
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@ -130,7 +130,6 @@
#![feature(const_trait_impl)]
#![feature(const_type_id)]
#![feature(const_type_name)]
#![feature(const_unreachable_unchecked)]
#![feature(const_default_impls)]
#![feature(duration_consts_2)]
#![feature(ptr_metadata)]