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reitermarkusreitermarkus
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Make NonZero constructors generic.
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‎library/core/src/num/nonzero.rs

+84-71
Original file line numberDiff line numberDiff line change
@@ -83,6 +83,90 @@ impl_zeroable_primitive!(isize);
8383
#[rustc_diagnostic_item = "NonZero"]
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pub struct NonZero<T: ZeroablePrimitive>(T);
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86+
impl<T> NonZero<T>
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where
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T: ZeroablePrimitive,
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{
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/// Creates a non-zero if the given value is not zero.
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#[stable(feature = "nonzero", since = "1.28.0")]
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#[rustc_const_stable(feature = "const_nonzero_int_methods", since = "1.47.0")]
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#[rustc_allow_const_fn_unstable(const_refs_to_cell)]
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#[must_use]
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#[inline]
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pub const fn new(n: T) -> Option<Self> {
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// SAFETY: Memory layout optimization guarantees that `Option<NonZero<T>>` has
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// the same layout and size as `T`, with `0` representing `None`.
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unsafe { crate::mem::transmute_copy(&n) }
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}
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/// Creates a non-zero without checking whether the value is non-zero.
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/// This results in undefined behaviour if the value is zero.
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///
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/// # Safety
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///
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/// The value must not be zero.
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#[stable(feature = "nonzero", since = "1.28.0")]
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#[rustc_const_stable(feature = "nonzero", since = "1.28.0")]
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#[must_use]
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#[inline]
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pub const unsafe fn new_unchecked(n: T) -> Self {
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match Self::new(n) {
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Some(n) => n,
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None => {
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// SAFETY: The caller guarantees that `n` is non-zero, so this is unreachable.
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unsafe {
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crate::intrinsics::assert_unsafe_precondition!(
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"NonZero::new_unchecked requires the argument to be non-zero",
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() => false
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);
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crate::hint::unreachable_unchecked()
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}
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}
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}
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}
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/// Converts a reference to a non-zero mutable reference
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/// if the referenced value is not zero.
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#[unstable(feature = "nonzero_from_mut", issue = "106290")]
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#[must_use]
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#[inline]
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pub fn from_mut(n: &mut T) -> Option<&mut Self> {
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// SAFETY: Memory layout optimization guarantees that `Option<NonZero<T>>` has
136+
// the same layout and size as `T`, with `0` representing `None`.
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let opt_n = unsafe { &mut *(n as *mut T as *mut Option<Self>) };
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opt_n.as_mut()
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}
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/// Converts a mutable reference to a non-zero mutable reference
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/// without checking whether the referenced value is non-zero.
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/// This results in undefined behavior if the referenced value is zero.
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///
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/// # Safety
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///
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/// The referenced value must not be zero.
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#[unstable(feature = "nonzero_from_mut", issue = "106290")]
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#[must_use]
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#[inline]
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pub unsafe fn from_mut_unchecked(n: &mut T) -> &mut Self {
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match Self::from_mut(n) {
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Some(n) => n,
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None => {
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// SAFETY: The caller guarantees that `n` references a value that is non-zero, so this is unreachable.
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unsafe {
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crate::intrinsics::assert_unsafe_precondition!(
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"NonZero::from_mut_unchecked requires the argument to dereference as non-zero",
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() => false
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);
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crate::hint::unreachable_unchecked()
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}
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}
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}
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}
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}
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macro_rules! impl_nonzero_fmt {
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( #[$stability: meta] ( $( $Trait: ident ),+ ) for $Ty: ident ) => {
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$(
@@ -100,7 +184,6 @@ macro_rules! impl_nonzero_fmt {
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macro_rules! nonzero_integer {
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(
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#[$stability:meta]
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#[$const_new_unchecked_stability:meta]
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Self = $Ty:ident,
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Primitive = $signedness:ident $Int:ident,
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$(UnsignedNonZero = $UnsignedNonZero:ident,)?
@@ -143,74 +226,6 @@ macro_rules! nonzero_integer {
143226
pub type $Ty = NonZero<$Int>;
144227

145228
impl $Ty {
146-
/// Creates a non-zero without checking whether the value is non-zero.
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/// This results in undefined behaviour if the value is zero.
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///
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/// # Safety
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///
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/// The value must not be zero.
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#[$stability]
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#[$const_new_unchecked_stability]
154-
#[must_use]
155-
#[inline]
156-
pub const unsafe fn new_unchecked(n: $Int) -> Self {
157-
crate::panic::debug_assert_nounwind!(
158-
n != 0,
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concat!(stringify!($Ty), "::new_unchecked requires a non-zero argument")
160-
);
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// SAFETY: this is guaranteed to be safe by the caller.
162-
unsafe {
163-
Self(n)
164-
}
165-
}
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167-
/// Creates a non-zero if the given value is not zero.
168-
#[$stability]
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#[rustc_const_stable(feature = "const_nonzero_int_methods", since = "1.47.0")]
170-
#[must_use]
171-
#[inline]
172-
pub const fn new(n: $Int) -> Option<Self> {
173-
if n != 0 {
174-
// SAFETY: we just checked that there's no `0`
175-
Some(unsafe { Self(n) })
176-
} else {
177-
None
178-
}
179-
}
180-
181-
/// Converts a primitive mutable reference to a non-zero mutable reference
182-
/// without checking whether the referenced value is non-zero.
183-
/// This results in undefined behavior if `*n` is zero.
184-
///
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/// # Safety
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/// The referenced value must not be currently zero.
187-
#[unstable(feature = "nonzero_from_mut", issue = "106290")]
188-
#[must_use]
189-
#[inline]
190-
pub unsafe fn from_mut_unchecked(n: &mut $Int) -> &mut Self {
191-
// SAFETY: Self is repr(transparent), and the value is assumed to be non-zero.
192-
unsafe {
193-
let n_alias = &mut *n;
194-
core::intrinsics::assert_unsafe_precondition!(
195-
concat!(stringify!($Ty), "::from_mut_unchecked requires the argument to dereference as non-zero"),
196-
(n_alias: &mut $Int) => *n_alias != 0
197-
);
198-
&mut *(n as *mut $Int as *mut Self)
199-
}
200-
}
201-
202-
/// Converts a primitive mutable reference to a non-zero mutable reference
203-
/// if the referenced integer is not zero.
204-
#[unstable(feature = "nonzero_from_mut", issue = "106290")]
205-
#[must_use]
206-
#[inline]
207-
pub fn from_mut(n: &mut $Int) -> Option<&mut Self> {
208-
// SAFETY: Self is repr(transparent), and the value is non-zero.
209-
// As long as the returned reference is alive,
210-
// the user cannot `*n = 0` directly.
211-
(*n != 0).then(|| unsafe { &mut *(n as *mut $Int as *mut Self) })
212-
}
213-
214229
/// Returns the value as a primitive type.
215230
#[$stability]
216231
#[inline]
@@ -724,7 +739,6 @@ macro_rules! nonzero_integer {
724739
(Self = $Ty:ident, Primitive = unsigned $Int:ident $(,)?) => {
725740
nonzero_integer! {
726741
#[stable(feature = "nonzero", since = "1.28.0")]
727-
#[rustc_const_stable(feature = "nonzero", since = "1.28.0")]
728742
Self = $Ty,
729743
Primitive = unsigned $Int,
730744
UnsignedPrimitive = $Int,
@@ -735,7 +749,6 @@ macro_rules! nonzero_integer {
735749
(Self = $Ty:ident, Primitive = signed $Int:ident, $($rest:tt)*) => {
736750
nonzero_integer! {
737751
#[stable(feature = "signed_nonzero", since = "1.34.0")]
738-
#[rustc_const_stable(feature = "signed_nonzero", since = "1.34.0")]
739752
Self = $Ty,
740753
Primitive = signed $Int,
741754
$($rest)*

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