Matthias Krüger 4d840a6e45
Rollup merge of #91823 - woppopo:const_ptr_as_ref, r=lcnr
Make `PTR::as_ref` and similar methods `const`.

Tracking issue: #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>];
}
```
2021-12-21 08:33:40 +01:00
..