Update mod.rs

Author: joshlf

library/core/src/ptr/mod.rs

@@ -66,10 +66,12 @@
 //! a separate allocated object), and `static` variables.
 //!
 //! It is guaranteed that an allocated object never spans more than `isize::MAX` bytes.
-//! An allocated object cannot contain the last (`usize::MAX`) byte of the address space.
-//! As a consequence, any address which is either in the allocated object or one byte past
-//! the last address in the allocated object can be computed without wrapping around the
-//! address space.
+//! An allocated object cannot contain [`null()`] and cannot contain the last (`usize::MAX`) byte
+//! of the address space. As a consequence, any address which is either in the allocated object or
+//! one byte past the last address in the allocated object can be computed without wrapping around
+//! the address space.
+//!
+//! [`null()`]: null
 //!
 //! # Strict Provenance
 //!