diff options
Diffstat (limited to '')
| -rw-r--r-- | library/alloc/src/vec/is_zero.rs | 22 |
1 files changed, 20 insertions, 2 deletions
diff --git a/library/alloc/src/vec/is_zero.rs b/library/alloc/src/vec/is_zero.rs index 8e652d676..cb9adf05c 100644 --- a/library/alloc/src/vec/is_zero.rs +++ b/library/alloc/src/vec/is_zero.rs @@ -4,7 +4,8 @@ use crate::boxed::Box; #[rustc_specialization_trait] pub(super) unsafe trait IsZero { - /// Whether this value's representation is all zeros + /// Whether this value's representation is all zeros, + /// or can be represented with all zeroes. fn is_zero(&self) -> bool; } @@ -57,7 +58,7 @@ unsafe impl<T: IsZero, const N: usize> IsZero for [T; N] { #[inline] fn is_zero(&self) -> bool { // Because this is generated as a runtime check, it's not obvious that - // it's worth doing if the array is really long. The threshold here + // it's worth doing if the array is really long. The threshold here // is largely arbitrary, but was picked because as of 2022-07-01 LLVM // fails to const-fold the check in `vec![[1; 32]; n]` // See https://github.com/rust-lang/rust/pull/97581#issuecomment-1166628022 @@ -147,6 +148,23 @@ impl_is_zero_option_of_nonzero!( NonZeroIsize, ); +macro_rules! impl_is_zero_option_of_num { + ($($t:ty,)+) => {$( + unsafe impl IsZero for Option<$t> { + #[inline] + fn is_zero(&self) -> bool { + const { + let none: Self = unsafe { core::mem::MaybeUninit::zeroed().assume_init() }; + assert!(none.is_none()); + } + self.is_none() + } + } + )+}; +} + +impl_is_zero_option_of_num!(u8, u16, u32, u64, u128, i8, i16, i32, i64, i128, usize, isize,); + unsafe impl<T: IsZero> IsZero for Wrapping<T> { #[inline] fn is_zero(&self) -> bool { |