Use a NonNull pointer

Author: Darksonn

library/core/src/panic/location.rs

@@ -1,6 +1,7 @@
 use crate::ffi::CStr;
 use crate::fmt;
 use crate::marker::PhantomData;
+use crate::ptr::NonNull;
 
 /// A struct containing information about the location of a panic.
 ///
@@ -37,7 +38,7 @@ pub struct Location<'a> {
     // A raw pointer is used rather than a reference because the pointer is valid for one more byte
     // than the length stored in this pointer; the additional byte is the NUL-terminator used by
     // `Location::file_with_nul`.
-    filename: *const str,
+    filename: NonNull<str>,
     line: u32,
     col: u32,
     _filename: PhantomData<&'a str>,
@@ -144,7 +145,7 @@ impl<'a> Location<'a> {
     #[rustc_const_stable(feature = "const_location_fields", since = "1.79.0")]
     pub const fn file(&self) -> &str {
         // SAFETY: The filename is valid.
-        unsafe { &*self.filename }
+        unsafe { self.filename.as_ref() }
     }
 
     /// Returns the name of the source file as a nul-terminated `CStr`.
@@ -155,12 +156,14 @@ impl<'a> Location<'a> {
     #[unstable(feature = "file_with_nul", issue = "141727")]
     #[inline]
     pub const fn file_with_nul(&self) -> &CStr {
+        let filename = self.filename.as_ptr();
+
         // SAFETY: The filename is valid for `filename_len+1` bytes, so this addition can't
         // overflow.
-        let cstr_len = unsafe { crate::mem::size_of_val_raw(self.filename).unchecked_add(1) };
+        let cstr_len = unsafe { crate::mem::size_of_val_raw(filename).unchecked_add(1) };
 
         // SAFETY: The filename is valid for `filename_len+1` bytes.
-        let slice = unsafe { crate::slice::from_raw_parts(self.filename as *const _, cstr_len) };
+        let slice = unsafe { crate::slice::from_raw_parts(filename.cast(), cstr_len) };
 
         // SAFETY: The filename is guaranteed to have a trailing nul byte and no interior nul bytes.
         unsafe { CStr::from_bytes_with_nul_unchecked(slice) }