Rollup merge of #127978 - nyurik:lib-refs, r=workingjubilee

Avoid ref when using format! for perf

Clean up a few minor refs in `format!` macro, as it has a performance cost. Apparently the compiler is unable to inline `format!("{}", &variable)`, and does a run-time double-reference instead (format macro already does one level referencing).  Inlining format args prevents accidental `&` misuse.

library/core/src/fmt/builders.rs

@@ -1026,7 +1026,7 @@ impl<'a, 'b: 'a> DebugMap<'a, 'b> {
 /// assert_eq!(format!("{}", value), "a");
 /// assert_eq!(format!("{:?}", value), "'a'");
 ///
-/// let wrapped = fmt::FormatterFn(|f| write!(f, "{:?}", &value));
+/// let wrapped = fmt::FormatterFn(|f| write!(f, "{value:?}"));
 /// assert_eq!(format!("{}", wrapped), "'a'");
 /// assert_eq!(format!("{:?}", wrapped), "'a'");
 /// ```

library/core/tests/future.rs

@@ -56,7 +56,7 @@ fn test_join() {
 
  let y = String::new();
  let x = join!(async {
- println!("{}", &y);
+ println!("{y}");
  1
  })
  .await;

library/proc_macro/src/lib.rs

@@ -1544,10 +1544,10 @@ impl fmt::Debug for Literal {
  fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
  f.debug_struct("Literal")
  // format the kind on one line even in {:#?} mode
- .field("kind", &format_args!("{:?}", &self.0.kind))
+ .field("kind", &format_args!("{:?}", self.0.kind))
  .field("symbol", &self.0.symbol)
  // format `Some("...")` on one line even in {:#?} mode
- .field("suffix", &format_args!("{:?}", &self.0.suffix))
+ .field("suffix", &format_args!("{:?}", self.0.suffix))
  .field("span", &self.0.span)
  .finish()
  }

library/std/src/fs/tests.rs

@@ -683,7 +683,7 @@ fn recursive_rmdir_toctou() {
  let drop_canary_arc = Arc::new(());
  let drop_canary_weak = Arc::downgrade(&drop_canary_arc);
 
- eprintln!("x: {:?}", &victim_del_path);
+ eprintln!("x: {victim_del_path:?}");
 
  // victim just continuously removes `victim_del`
  thread::spawn(move || {

library/std/src/io/error.rs

@@ -775,7 +775,7 @@ impl Error {
  ///
  /// impl Display for MyError {
  /// fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
- /// write!(f, "MyError: {}", &self.v)
+ /// write!(f, "MyError: {}", self.v)
  /// }
  /// }
  ///