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Rollup merge of rust-lang#91823 - woppopo:const_ptr_as_ref, r=lcnr
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Make `PTR::as_ref` and similar methods `const`.

Tracking issue: rust-lang#91822
Feature gate: `#![feature(const_ptr_as_ref)]`

```rust
// core::ptr
impl<T: ?Sized> *const T {
    pub const unsafe fn as_ref<'a>(self) -> Option<&'a T>;
    pub const unsafe fn as_uninit_ref<'a>(self) -> Option<&'a MaybeUninit<T>>
    where
        T: Sized;
    pub const unsafe fn as_uninit_slice<'a>(self) -> Option<&'a [MaybeUninit<T>]>;
}

impl<T: ?Sized> *mut T {
    pub const unsafe fn as_ref<'a>(self) -> Option<&'a T>;
    pub const unsafe fn as_uninit_ref<'a>(self) -> Option<&'a MaybeUninit<T>>
    where
        T: Sized;
    pub const unsafe fn as_mut<'a>(self) -> Option<&'a mut T>;
    pub const unsafe fn as_uninit_mut<'a>(self) -> Option<&'a mut MaybeUninit<T>>
    where
        T: Sized;
    pub const unsafe fn as_uninit_slice<'a>(self) -> Option<&'a [MaybeUninit<T>]>;
    pub const unsafe fn as_uninit_slice_mut<'a>(self) -> Option<&'a mut [MaybeUninit<T>]>;
}

impl<T: Sized> NonNull<T> {
    pub const unsafe fn as_uninit_ref<'a>(&self) -> &'a MaybeUninit<T>;
    pub const unsafe fn as_uninit_mut<'a>(&mut self) -> &'a mut MaybeUninit<T>;
}

impl<T: ?Sized> NonNull<T> {
    pub const unsafe fn as_ref<'a>(&self) -> &'a T;
    pub const unsafe fn as_mut<'a>(&mut self) -> &'a mut T;
    pub const unsafe fn as_uninit_slice<'a>(&self) -> &'a [MaybeUninit<T>];
    pub const unsafe fn as_uninit_slice_mut<'a>(&self) -> &'a mut [MaybeUninit<T>];
}
```
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@matthiaskrgr
matthiaskrgr authored Dec 21, 2021
2 parents 790950a + a4b3fe0 commit 4d840a6
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Showing 3 changed files with 30 additions and 15 deletions.
9 changes: 6 additions & 3 deletions library/core/src/ptr/const_ptr.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -163,8 +163,9 @@ impl<T: ?Sized> *const T {
/// }
/// ```
#[stable(feature = "ptr_as_ref", since = "1.9.0")]
#[rustc_const_unstable(feature = "const_ptr_as_ref", issue = "91822")]
#[inline]
pub unsafe fn as_ref<'a>(self) -> Option<&'a T> {
pub const unsafe fn as_ref<'a>(self) -> Option<&'a T> {
// SAFETY: the caller must guarantee that `self` is valid
// for a reference if it isn't null.
if self.is_null() { None } else { unsafe { Some(&*self) } }
Expand Down Expand Up @@ -211,7 +212,8 @@ impl<T: ?Sized> *const T {
/// ```
#[inline]
#[unstable(feature = "ptr_as_uninit", issue = "75402")]
pub unsafe fn as_uninit_ref<'a>(self) -> Option<&'a MaybeUninit<T>>
#[rustc_const_unstable(feature = "const_ptr_as_ref", issue = "91822")]
pub const unsafe fn as_uninit_ref<'a>(self) -> Option<&'a MaybeUninit<T>>
where
T: Sized,
{
Expand Down Expand Up @@ -1068,7 +1070,8 @@ impl<T> *const [T] {
/// [allocated object]: crate::ptr#allocated-object
#[inline]
#[unstable(feature = "ptr_as_uninit", issue = "75402")]
pub unsafe fn as_uninit_slice<'a>(self) -> Option<&'a [MaybeUninit<T>]> {
#[rustc_const_unstable(feature = "const_ptr_as_ref", issue = "91822")]
pub const unsafe fn as_uninit_slice<'a>(self) -> Option<&'a [MaybeUninit<T>]> {
if self.is_null() {
None
} else {
Expand Down
18 changes: 12 additions & 6 deletions library/core/src/ptr/mut_ptr.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -166,8 +166,9 @@ impl<T: ?Sized> *mut T {
/// }
/// ```
#[stable(feature = "ptr_as_ref", since = "1.9.0")]
#[rustc_const_unstable(feature = "const_ptr_as_ref", issue = "91822")]
#[inline]
pub unsafe fn as_ref<'a>(self) -> Option<&'a T> {
pub const unsafe fn as_ref<'a>(self) -> Option<&'a T> {
// SAFETY: the caller must guarantee that `self` is valid for a
// reference if it isn't null.
if self.is_null() { None } else { unsafe { Some(&*self) } }
Expand Down Expand Up @@ -217,7 +218,8 @@ impl<T: ?Sized> *mut T {
/// ```
#[inline]
#[unstable(feature = "ptr_as_uninit", issue = "75402")]
pub unsafe fn as_uninit_ref<'a>(self) -> Option<&'a MaybeUninit<T>>
#[rustc_const_unstable(feature = "const_ptr_as_ref", issue = "91822")]
pub const unsafe fn as_uninit_ref<'a>(self) -> Option<&'a MaybeUninit<T>>
where
T: Sized,
{
Expand Down Expand Up @@ -411,8 +413,9 @@ impl<T: ?Sized> *mut T {
/// println!("{:?}", s); // It'll print: "[4, 2, 3]".
/// ```
#[stable(feature = "ptr_as_ref", since = "1.9.0")]
#[rustc_const_unstable(feature = "const_ptr_as_ref", issue = "91822")]
#[inline]
pub unsafe fn as_mut<'a>(self) -> Option<&'a mut T> {
pub const unsafe fn as_mut<'a>(self) -> Option<&'a mut T> {
// SAFETY: the caller must guarantee that `self` is be valid for
// a mutable reference if it isn't null.
if self.is_null() { None } else { unsafe { Some(&mut *self) } }
Expand Down Expand Up @@ -446,7 +449,8 @@ impl<T: ?Sized> *mut T {
/// [the module documentation]: crate::ptr#safety
#[inline]
#[unstable(feature = "ptr_as_uninit", issue = "75402")]
pub unsafe fn as_uninit_mut<'a>(self) -> Option<&'a mut MaybeUninit<T>>
#[rustc_const_unstable(feature = "const_ptr_as_ref", issue = "91822")]
pub const unsafe fn as_uninit_mut<'a>(self) -> Option<&'a mut MaybeUninit<T>>
where
T: Sized,
{
Expand Down Expand Up @@ -1335,7 +1339,8 @@ impl<T> *mut [T] {
/// [allocated object]: crate::ptr#allocated-object
#[inline]
#[unstable(feature = "ptr_as_uninit", issue = "75402")]
pub unsafe fn as_uninit_slice<'a>(self) -> Option<&'a [MaybeUninit<T>]> {
#[rustc_const_unstable(feature = "const_ptr_as_ref", issue = "91822")]
pub const unsafe fn as_uninit_slice<'a>(self) -> Option<&'a [MaybeUninit<T>]> {
if self.is_null() {
None
} else {
Expand Down Expand Up @@ -1386,7 +1391,8 @@ impl<T> *mut [T] {
/// [allocated object]: crate::ptr#allocated-object
#[inline]
#[unstable(feature = "ptr_as_uninit", issue = "75402")]
pub unsafe fn as_uninit_slice_mut<'a>(self) -> Option<&'a mut [MaybeUninit<T>]> {
#[rustc_const_unstable(feature = "const_ptr_as_ref", issue = "91822")]
pub const unsafe fn as_uninit_slice_mut<'a>(self) -> Option<&'a mut [MaybeUninit<T>]> {
if self.is_null() {
None
} else {
Expand Down
18 changes: 12 additions & 6 deletions library/core/src/ptr/non_null.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -122,7 +122,8 @@ impl<T: Sized> NonNull<T> {
#[inline]
#[must_use]
#[unstable(feature = "ptr_as_uninit", issue = "75402")]
pub unsafe fn as_uninit_ref<'a>(&self) -> &'a MaybeUninit<T> {
#[rustc_const_unstable(feature = "const_ptr_as_ref", issue = "91822")]
pub const unsafe fn as_uninit_ref<'a>(&self) -> &'a MaybeUninit<T> {
// SAFETY: the caller must guarantee that `self` meets all the
// requirements for a reference.
unsafe { &*self.cast().as_ptr() }
Expand Down Expand Up @@ -155,7 +156,8 @@ impl<T: Sized> NonNull<T> {
#[inline]
#[must_use]
#[unstable(feature = "ptr_as_uninit", issue = "75402")]
pub unsafe fn as_uninit_mut<'a>(&mut self) -> &'a mut MaybeUninit<T> {
#[rustc_const_unstable(feature = "const_ptr_as_ref", issue = "91822")]
pub const unsafe fn as_uninit_mut<'a>(&mut self) -> &'a mut MaybeUninit<T> {
// SAFETY: the caller must guarantee that `self` meets all the
// requirements for a reference.
unsafe { &mut *self.cast().as_ptr() }
Expand Down Expand Up @@ -316,9 +318,10 @@ impl<T: ?Sized> NonNull<T> {
///
/// [the module documentation]: crate::ptr#safety
#[stable(feature = "nonnull", since = "1.25.0")]
#[rustc_const_unstable(feature = "const_ptr_as_ref", issue = "91822")]
#[must_use]
#[inline]
pub unsafe fn as_ref<'a>(&self) -> &'a T {
pub const unsafe fn as_ref<'a>(&self) -> &'a T {
// SAFETY: the caller must guarantee that `self` meets all the
// requirements for a reference.
unsafe { &*self.as_ptr() }
Expand Down Expand Up @@ -366,9 +369,10 @@ impl<T: ?Sized> NonNull<T> {
///
/// [the module documentation]: crate::ptr#safety
#[stable(feature = "nonnull", since = "1.25.0")]
#[rustc_const_unstable(feature = "const_ptr_as_ref", issue = "91822")]
#[must_use]
#[inline]
pub unsafe fn as_mut<'a>(&mut self) -> &'a mut T {
pub const unsafe fn as_mut<'a>(&mut self) -> &'a mut T {
// SAFETY: the caller must guarantee that `self` meets all the
// requirements for a mutable reference.
unsafe { &mut *self.as_ptr() }
Expand Down Expand Up @@ -534,7 +538,8 @@ impl<T> NonNull<[T]> {
#[inline]
#[must_use]
#[unstable(feature = "ptr_as_uninit", issue = "75402")]
pub unsafe fn as_uninit_slice<'a>(&self) -> &'a [MaybeUninit<T>] {
#[rustc_const_unstable(feature = "const_ptr_as_ref", issue = "91822")]
pub const unsafe fn as_uninit_slice<'a>(&self) -> &'a [MaybeUninit<T>] {
// SAFETY: the caller must uphold the safety contract for `as_uninit_slice`.
unsafe { slice::from_raw_parts(self.cast().as_ptr(), self.len()) }
}
Expand Down Expand Up @@ -596,7 +601,8 @@ impl<T> NonNull<[T]> {
#[inline]
#[must_use]
#[unstable(feature = "ptr_as_uninit", issue = "75402")]
pub unsafe fn as_uninit_slice_mut<'a>(&self) -> &'a mut [MaybeUninit<T>] {
#[rustc_const_unstable(feature = "const_ptr_as_ref", issue = "91822")]
pub const unsafe fn as_uninit_slice_mut<'a>(&self) -> &'a mut [MaybeUninit<T>] {
// SAFETY: the caller must uphold the safety contract for `as_uninit_slice_mut`.
unsafe { slice::from_raw_parts_mut(self.cast().as_ptr(), self.len()) }
}
Expand Down

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