Stabilize file_as_c_str

Author: Darksonn

library/core/src/panic/location.rs

@@ -193,9 +193,10 @@ impl<'a> Location<'a> {
     /// This is useful for interop with APIs that expect C/C++ `__FILE__` or
     /// `std::source_location::file_name`, both of which return a nul-terminated `const char*`.
     #[must_use]
-    #[unstable(feature = "file_with_nul", issue = "141727")]
     #[inline]
-    pub const fn file_as_c_str(&self) -> &'a CStr {
+    #[stable(feature = "file_with_nul", since = "CURRENT_RUSTC_VERSION")]
+    #[rustc_const_stable(feature = "file_with_nul", since = "CURRENT_RUSTC_VERSION")]
+    pub const fn file_as_c_str(&self) -> &CStr {
         let filename = self.filename.as_ptr();
 
         // SAFETY: The filename is valid for `filename_len+1` bytes, so this addition can't

tests/ui/rfcs/rfc-2091-track-caller/file-is-nul-terminated.rs

@@ -1,5 +1,4 @@
 //@ run-pass
-#![feature(file_with_nul)]
 
 #[track_caller]
 const fn assert_file_has_trailing_zero() {