Use as_deref in compiler (but only where it makes sense)

compiler/rustc_span/src/lib.rs

@@ -217,9 +217,7 @@ impl RealFileName {
     pub fn local_path(&self) -> Option<&Path> {
         match self {
             RealFileName::LocalPath(p) => Some(p),
-            RealFileName::Remapped { local_path: p, virtual_name: _ } => {
-                p.as_ref().map(PathBuf::as_path)
-            }
+            RealFileName::Remapped { local_path, virtual_name: _ } => local_path.as_deref(),
         }
     }