From 1042b5df9bbfa29e87c09edb54aaeb667336d1b4 Mon Sep 17 00:00:00 2001
From: Scott McMurray <scottmcm@users.noreply.github.com>
Date: Fri, 7 Apr 2023 01:32:12 -0700
Subject: [PATCH] Avoid some manual slice length calculation

No need for us to write the multiplication when `size_of_val` does exactly what we need.
---
 library/core/src/mem/maybe_uninit.rs | 16 ++++------------
 1 file changed, 4 insertions(+), 12 deletions(-)

diff --git a/library/core/src/mem/maybe_uninit.rs b/library/core/src/mem/maybe_uninit.rs
index 3f491836551..9c6d48675a6 100644
--- a/library/core/src/mem/maybe_uninit.rs
+++ b/library/core/src/mem/maybe_uninit.rs
@@ -1241,13 +1241,9 @@ pub fn as_bytes_mut(&mut self) -> &mut [MaybeUninit<u8>] {
     /// ```
     #[unstable(feature = "maybe_uninit_as_bytes", issue = "93092")]
     pub fn slice_as_bytes(this: &[MaybeUninit<T>]) -> &[MaybeUninit<u8>] {
+        let bytes = mem::size_of_val(this);
         // SAFETY: MaybeUninit<u8> is always valid, even for padding bytes
-        unsafe {
-            slice::from_raw_parts(
-                this.as_ptr() as *const MaybeUninit<u8>,
-                this.len() * mem::size_of::<T>(),
-            )
-        }
+        unsafe { slice::from_raw_parts(this.as_ptr() as *const MaybeUninit<u8>, bytes) }
     }
 
     /// Returns the contents of this mutable slice of `MaybeUninit` as a mutable slice of
@@ -1274,13 +1270,9 @@ pub fn slice_as_bytes(this: &[MaybeUninit<T>]) -> &[MaybeUninit<u8>] {
     /// ```
     #[unstable(feature = "maybe_uninit_as_bytes", issue = "93092")]
     pub fn slice_as_bytes_mut(this: &mut [MaybeUninit<T>]) -> &mut [MaybeUninit<u8>] {
+        let bytes = mem::size_of_val(this);
         // SAFETY: MaybeUninit<u8> is always valid, even for padding bytes
-        unsafe {
-            slice::from_raw_parts_mut(
-                this.as_mut_ptr() as *mut MaybeUninit<u8>,
-                this.len() * mem::size_of::<T>(),
-            )
-        }
+        unsafe { slice::from_raw_parts_mut(this.as_mut_ptr() as *mut MaybeUninit<u8>, bytes) }
     }
 }