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Mark {array,slice}::{from_ref,from_mut} as const fn

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Maybe Waffle
2021-10-22 11:15:56 +03:00
parent 1d6f24210c
commit a288bf6afb
3 changed files with 10 additions and 4 deletions
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6
library/core/src/array/mod.rs
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@@ -85,14 +85,16 @@ where
/// Converts a reference to `T` into a reference to an array of length 1 (without copying).
#[stable(feature = "array_from_ref", since = "1.53.0")]
pub fn from_ref<T>(s: &T) -> &[T; 1] {
#[rustc_const_unstable(feature = "const_array_from_ref", issue = "none")]
pub const fn from_ref<T>(s: &T) -> &[T; 1] {
// SAFETY: Converting `&T` to `&[T; 1]` is sound.
unsafe { &*(s as *const T).cast::<[T; 1]>() }
}
/// Converts a mutable reference to `T` into a mutable reference to an array of length 1 (without copying).
#[stable(feature = "array_from_ref", since = "1.53.0")]
pub fn from_mut<T>(s: &mut T) -> &mut [T; 1] {
#[rustc_const_unstable(feature = "const_array_from_ref", issue = "none")]
pub const fn from_mut<T>(s: &mut T) -> &mut [T; 1] {
// SAFETY: Converting `&mut T` to `&mut [T; 1]` is sound.
unsafe { &mut *(s as *mut T).cast::<[T; 1]>() }
}