Improve #Safety in various methods in core::ptr

s/for reads and writes/for both ...

Author: amosonn

src/libcore/ptr/mod.rs

@@ -289,7 +289,7 @@ pub const fn slice_from_raw_parts_mut<T>(data: *mut T, len: usize) -> *mut [T] {
 ///
 /// Behavior is undefined if any of the following conditions are violated:
 ///
-/// * Both `x` and `y` must be [valid] for reads and writes.
+/// * Both `x` and `y` must be [valid] for both reads and writes.
 ///
 /// * Both `x` and `y` must be properly aligned.
 ///
@@ -355,7 +355,7 @@ pub unsafe fn swap<T>(x: *mut T, y: *mut T) {
 ///
 /// Behavior is undefined if any of the following conditions are violated:
 ///
-/// * Both `x` and `y` must be [valid] for reads and writes of `count *
+/// * Both `x` and `y` must be [valid] for both reads and writes of `count *
 ///   size_of::<T>()` bytes.
 ///
 /// * Both `x` and `y` must be properly aligned.