Rollup merge of #91806 - woppopo:const_unique, r=dtolnay

Make `Unique`s methods `const`

Tracking issue: None

library/core/src/lib.rs

@@ -124,6 +124,7 @@
 #![feature(const_option)]
 #![feature(const_pin)]
 #![feature(const_replace)]
+#![feature(const_ptr_is_null)]
 #![feature(const_ptr_offset)]
 #![feature(const_ptr_offset_from)]
 #![feature(const_ptr_read)]

library/core/src/ptr/unique.rs

@@ -92,7 +92,7 @@ impl<T: ?Sized> Unique<T> {
 
     /// Creates a new `Unique` if `ptr` is non-null.
     #[inline]
-    pub fn new(ptr: *mut T) -> Option<Self> {
+    pub const fn new(ptr: *mut T) -> Option<Self> {
         if !ptr.is_null() {
             // SAFETY: The pointer has already been checked and is not null.
             Some(unsafe { Unique { pointer: ptr as _, _marker: PhantomData } })
@@ -115,7 +115,7 @@ impl<T: ?Sized> Unique<T> {
     /// (unbound) lifetime is needed, use `&*my_ptr.as_ptr()`.
     #[must_use]
     #[inline]
-    pub unsafe fn as_ref(&self) -> &T {
+    pub const unsafe fn as_ref(&self) -> &T {
         // SAFETY: the caller must guarantee that `self` meets all the
         // requirements for a reference.
         unsafe { &*self.as_ptr() }
@@ -128,7 +128,7 @@ impl<T: ?Sized> Unique<T> {
     /// (unbound) lifetime is needed, use `&mut *my_ptr.as_ptr()`.
     #[must_use]
     #[inline]
-    pub unsafe fn as_mut(&mut self) -> &mut T {
+    pub const unsafe fn as_mut(&mut self) -> &mut T {
         // SAFETY: the caller must guarantee that `self` meets all the
         // requirements for a mutable reference.
         unsafe { &mut *self.as_ptr() }