NFC: Use pointer::cast instead of as for pointer casts.

Enforce this pattern with Clippy.

src/aead/aes.rs

@@ -114,8 +114,8 @@ fn ctr32_encrypt_blocks_(
     let blocks_u32 = blocks as u32;
     assert_eq!(blocks, polyfill::usize_from_u32(blocks_u32));
 
-    let input = in_out[src].as_ptr() as *const [u8; BLOCK_LEN];
-    let output = in_out.as_mut_ptr() as *mut [u8; BLOCK_LEN];
+    let input = in_out[src].as_ptr().cast::<[u8; BLOCK_LEN]>();
+    let output = in_out.as_mut_ptr().cast::<[u8; BLOCK_LEN]>();
 
     unsafe {
         f(input, output, blocks, key, ctr);

src/aead/gcm.rs

@@ -124,7 +124,7 @@ impl Context {
         debug_assert_eq!(input_bytes % BLOCK_LEN, 0);
         debug_assert!(input_bytes > 0);
 
-        let input = input.as_ptr() as *const [u8; BLOCK_LEN];
+        let input = input.as_ptr().cast::<[u8; BLOCK_LEN]>();
         // SAFETY:
         // - `[[u8; BLOCK_LEN]]` has the same bit validity as `[u8]`.
         // - `[[u8; BLOCK_LEN]]` has the same alignment requirement as `[u8]`.

src/digest/sha1.rs

@@ -40,7 +40,7 @@ pub(super) extern "C" fn block_data_order(
 ) {
     let state = unsafe { &mut state.as32 };
     let state: &mut State = (&mut state[..CHAINING_WORDS]).try_into().unwrap();
-    let data = data as *const [<W32 as Word>::InputBytes; 16];
+    let data = data.cast::<[<W32 as Word>::InputBytes; 16]>();
     let blocks = unsafe { core::slice::from_raw_parts(data, num) };
     *state = block_data_order_(*state, blocks)
 }

src/digest/sha2.rs

@@ -48,7 +48,7 @@ fn block_data_order<S: Sha2>(
     M: *const u8,
     num: c::size_t,
 ) -> [S; CHAINING_WORDS] {
-    let M = M as *const [S::InputBytes; 16];
+    let M = M.cast::<[S::InputBytes; 16]>();
     let M: &[[S::InputBytes; 16]] = unsafe { core::slice::from_raw_parts(M, num) };
 
     for M in M {

src/endian.rs

@@ -32,8 +32,9 @@ macro_rules! impl_array_encoding {
         {
             #[inline]
             fn as_byte_array(&self) -> &[u8; $elems * core::mem::size_of::<$base>()] {
-                let as_bytes_ptr =
-                    self.as_ptr() as *const [u8; $elems * core::mem::size_of::<$base>()];
+                let as_bytes_ptr = self
+                    .as_ptr()
+                    .cast::<[u8; $elems * core::mem::size_of::<$base>()]>();
                 unsafe { &*as_bytes_ptr }
             }
         }

src/lib.rs

@@ -54,7 +54,8 @@
     invalid_reference_casting,
     clippy::char_lit_as_u8,
     clippy::fn_to_numeric_cast,
-    clippy::fn_to_numeric_cast_with_truncation
+    clippy::fn_to_numeric_cast_with_truncation,
+    clippy::ptr_as_ptr
 )]
 #![warn(
     clippy::unnecessary_cast,

src/polyfill/chunks_fixed.rs

@@ -18,8 +18,8 @@ macro_rules! define_chunks_fixed {
         {
             #[inline(always)]
             fn chunks_fixed(self) -> &'a [[T; $chunk_len]; $chunked_len] {
-                let as_ptr: *const [T; $chunk_len] = self.as_ptr() as *const [T; $chunk_len];
-                let as_ptr = as_ptr as *const [[T; $chunk_len]; $chunked_len];
+                let as_ptr = self.as_ptr().cast::<[T; $chunk_len]>();
+                let as_ptr = as_ptr.cast::<[[T; $chunk_len]; $chunked_len]>();
                 unsafe { &*as_ptr }
             }
         }