Add '<[T]>::as_array', '<[T]>::as_mut_array', '<*const [T]>::as_array', and '<*mut [T]>::as_mut_array' conversion methods;

library/core/src/array/mod.rs

@@ -214,8 +214,8 @@ impl<T, const N: usize> BorrowMut<[T]> for [T; N] {
     }
 }
 
-/// Tries to create an array `[T; N]` by copying from a slice `&[T]`. Succeeds if
-/// `slice.len() == N`.
+/// Tries to create an array `[T; N]` by copying from a slice `&[T]`.
+/// Succeeds if `slice.len() == N`.
 ///
 /// ```
 /// let bytes: [u8; 3] = [1, 0, 2];
@@ -282,13 +282,7 @@ impl<'a, T, const N: usize> TryFrom<&'a [T]> for &'a [T; N] {
 
     #[inline]
     fn try_from(slice: &'a [T]) -> Result<&'a [T; N], TryFromSliceError> {
-        if slice.len() == N {
-            let ptr = slice.as_ptr() as *const [T; N];
-            // SAFETY: ok because we just checked that the length fits
-            unsafe { Ok(&*ptr) }
-        } else {
-            Err(TryFromSliceError(()))
-        }
+        slice.as_array().ok_or(TryFromSliceError(()))
     }
 }
 
@@ -310,13 +304,7 @@ impl<'a, T, const N: usize> TryFrom<&'a mut [T]> for &'a mut [T; N] {
 
     #[inline]
     fn try_from(slice: &'a mut [T]) -> Result<&'a mut [T; N], TryFromSliceError> {
-        if slice.len() == N {
-            let ptr = slice.as_mut_ptr() as *mut [T; N];
-            // SAFETY: ok because we just checked that the length fits
-            unsafe { Ok(&mut *ptr) }
-        } else {
-            Err(TryFromSliceError(()))
-        }
+        slice.as_mut_array().ok_or(TryFromSliceError(()))
     }
 }