Reduce use of NonNull::new_unchecked in library/

library/alloc/src/raw_vec.rs

@@ -207,11 +207,7 @@ fn allocate_in(capacity: usize, init: AllocInit, alloc: A) -> Self {
             // Allocators currently return a `NonNull<[u8]>` whose length
             // matches the size requested. If that ever changes, the capacity
             // here should change to `ptr.len() / mem::size_of::<T>()`.
-            Self {
-                ptr: unsafe { Unique::new_unchecked(ptr.cast().as_ptr()) },
-                cap: unsafe { Cap(capacity) },
-                alloc,
-            }
+            Self { ptr: Unique::from(ptr.cast()), cap: unsafe { Cap(capacity) }, alloc }
         }
     }
 
@@ -239,6 +235,11 @@ pub fn ptr(&self) -> *mut T {
         self.ptr.as_ptr()
     }
 
+    #[inline]
+    pub fn non_null(&self) -> NonNull<T> {
+        NonNull::from(self.ptr)
+    }
+
     /// Gets the capacity of the allocation.
     ///
     /// This will always be `usize::MAX` if `T` is zero-sized.
@@ -398,7 +399,7 @@ unsafe fn set_ptr_and_cap(&mut self, ptr: NonNull<[u8]>, cap: usize) {
         // Allocators currently return a `NonNull<[u8]>` whose length matches
         // the size requested. If that ever changes, the capacity here should
         // change to `ptr.len() / mem::size_of::<T>()`.
-        self.ptr = unsafe { Unique::new_unchecked(ptr.cast().as_ptr()) };
+        self.ptr = Unique::from(ptr.cast());
         self.cap = unsafe { Cap(cap) };
     }
 

library/alloc/src/vec/into_iter.rs

@@ -136,7 +136,7 @@ pub(super) fn forget_allocation_drop_remaining(&mut self) {
         // struct and then overwriting &mut self.
         // this creates less assembly
         self.cap = 0;
-        self.buf = unsafe { NonNull::new_unchecked(RawVec::NEW.ptr()) };
+        self.buf = RawVec::NEW.non_null();
         self.ptr = self.buf;
         self.end = self.buf.as_ptr();
 

library/alloc/src/vec/mod.rs

@@ -2861,16 +2861,16 @@ impl<T, A: Allocator> IntoIterator for Vec<T, A> {
     #[inline]
     fn into_iter(self) -> Self::IntoIter {
         unsafe {
-            let mut me = ManuallyDrop::new(self);
+            let me = ManuallyDrop::new(self);
             let alloc = ManuallyDrop::new(ptr::read(me.allocator()));
-            let begin = me.as_mut_ptr();
+            let buf = me.buf.non_null();
+            let begin = buf.as_ptr();
             let end = if T::IS_ZST {
                 begin.wrapping_byte_add(me.len())
             } else {
                 begin.add(me.len()) as *const T
             };
             let cap = me.buf.capacity();
-            let buf = NonNull::new_unchecked(begin);
             IntoIter { buf, phantom: PhantomData, cap, alloc, ptr: buf, end }
         }
     }

library/core/src/ptr/non_null.rs

@@ -473,7 +473,7 @@ pub const fn as_ptr(self) -> *mut T {
     #[inline]
     pub const fn cast<U>(self) -> NonNull<U> {
         // SAFETY: `self` is a `NonNull` pointer which is necessarily non-null
-        unsafe { NonNull::new_unchecked(self.as_ptr() as *mut U) }
+        unsafe { NonNull { pointer: self.as_ptr() as *mut U } }
     }
 
     /// Calculates the offset from a pointer.
@@ -1828,9 +1828,8 @@ fn hash<H: hash::Hasher>(&self, state: &mut H) {
 impl<T: ?Sized> From<Unique<T>> for NonNull<T> {
     #[inline]
     fn from(unique: Unique<T>) -> Self {
-        // SAFETY: A Unique pointer cannot be null, so the conditions for
-        // new_unchecked() are respected.
-        unsafe { NonNull::new_unchecked(unique.as_ptr()) }
+        // SAFETY: A Unique pointer cannot be null.
+        unsafe { NonNull { pointer: unique.as_ptr() } }
     }
 }
 
@@ -1853,8 +1852,7 @@ impl<T: ?Sized> From<&T> for NonNull<T> {
     /// This conversion is safe and infallible since references cannot be null.
     #[inline]
     fn from(reference: &T) -> Self {
-        // SAFETY: A reference cannot be null, so the conditions for
-        // new_unchecked() are respected.
+        // SAFETY: A reference cannot be null.
         unsafe { NonNull { pointer: reference as *const T } }
     }
 }

library/core/src/ptr/unique.rs

@@ -138,7 +138,7 @@ pub const fn as_ptr(self) -> *mut T {
     pub const fn cast<U>(self) -> Unique<U> {
         // FIXME(const-hack): replace with `From`
         // SAFETY: is `NonNull`
-        unsafe { Unique::new_unchecked(self.pointer.cast().as_ptr()) }
+        Unique { pointer: self.pointer.cast(), _marker: PhantomData }
     }
 }
 

library/core/src/slice/iter.rs

@@ -87,12 +87,13 @@ unsafe impl<T: Sync> Send for Iter<'_, T> {}
 impl<'a, T> Iter<'a, T> {
     #[inline]
     pub(super) fn new(slice: &'a [T]) -> Self {
-        let ptr = slice.as_ptr();
+        let len = slice.len();
+        let ptr: NonNull<T> = NonNull::from(slice).cast();
         // SAFETY: Similar to `IterMut::new`.
         unsafe {
-            let end_or_len = if T::IS_ZST { invalid(slice.len()) } else { ptr.add(slice.len()) };
+            let end_or_len = if T::IS_ZST { invalid(len) } else { ptr.as_ptr().add(len) };
 
-            Self { ptr: NonNull::new_unchecked(ptr as *mut T), end_or_len, _marker: PhantomData }
+            Self { ptr, end_or_len, _marker: PhantomData }
         }
     }
 
@@ -208,7 +209,8 @@ unsafe impl<T: Send> Send for IterMut<'_, T> {}
 impl<'a, T> IterMut<'a, T> {
     #[inline]
     pub(super) fn new(slice: &'a mut [T]) -> Self {
-        let ptr = slice.as_mut_ptr();
+        let len = slice.len();
+        let ptr: NonNull<T> = NonNull::from(slice).cast();
         // SAFETY: There are several things here:
         //
         // `ptr` has been obtained by `slice.as_ptr()` where `slice` is a valid
@@ -226,10 +228,9 @@ pub(super) fn new(slice: &'a mut [T]) -> Self {
         // See the `next_unchecked!` and `is_empty!` macros as well as the
         // `post_inc_start` method for more information.
         unsafe {
-            let end_or_len =
-                if T::IS_ZST { invalid_mut(slice.len()) } else { ptr.add(slice.len()) };
+            let end_or_len = if T::IS_ZST { invalid_mut(len) } else { ptr.as_ptr().add(len) };
 
-            Self { ptr: NonNull::new_unchecked(ptr), end_or_len, _marker: PhantomData }
+            Self { ptr, end_or_len, _marker: PhantomData }
         }
     }