constify Location methods

Author: lilasta

library/core/src/panic/location.rs

@@ -123,8 +123,9 @@ impl<'a> Location<'a> {
     /// ```
     #[must_use]
     #[stable(feature = "panic_hooks", since = "1.10.0")]
+    #[rustc_const_unstable(feature = "const_caller_location", issue = "76156")]
     #[inline]
-    pub fn file(&self) -> &str {
+    pub const fn file(&self) -> &str {
         self.file
     }
 
@@ -147,8 +148,9 @@ impl<'a> Location<'a> {
     /// ```
     #[must_use]
     #[stable(feature = "panic_hooks", since = "1.10.0")]
+    #[rustc_const_unstable(feature = "const_caller_location", issue = "76156")]
     #[inline]
-    pub fn line(&self) -> u32 {
+    pub const fn line(&self) -> u32 {
         self.line
     }
 
@@ -171,8 +173,9 @@ impl<'a> Location<'a> {
     /// ```
     #[must_use]
     #[stable(feature = "panic_col", since = "1.25.0")]
+    #[rustc_const_unstable(feature = "const_caller_location", issue = "76156")]
     #[inline]
-    pub fn column(&self) -> u32 {
+    pub const fn column(&self) -> u32 {
         self.col
     }
 }