Rollup merge of rust-lang#127355 - aceArt-GmbH:126475, r=oli-obk

Mark format! with must_use hint

Uses unstable feature rust-lang#94745

Part of rust-lang#126475

First contribution to rust, please let me know if the blessing of tests is correct
Thanks `@bjorn3` for the help

tests/ui/or_fun_call.fixed

@@ -98,7 +98,7 @@ fn or_fun_call() {
 
  let opt = Some(1);
  let hello = "Hello";
- let _ = opt.ok_or(format!("{} world.", hello));
+ let _ = opt.ok_or_else(|| format!("{} world.", hello));
 
  // index
  let map = HashMap::<u64, u64>::new();

tests/ui/or_fun_call.stderr

@@ -100,6 +100,12 @@ error: use of `unwrap_or` to construct default value
 LL | let _ = stringy.unwrap_or(String::new());
  | ^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `unwrap_or_default()`
 
+error: use of `ok_or` followed by a function call
+ --> tests/ui/or_fun_call.rs:101:17
+ |
+LL | let _ = opt.ok_or(format!("{} world.", hello));
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `ok_or_else(|| format!("{} world.", hello))`
+
 error: use of `unwrap_or` followed by a function call
  --> tests/ui/or_fun_call.rs:105:21
  |
@@ -190,5 +196,5 @@ error: use of `unwrap_or_else` to construct default value
 LL | let _ = stringy.unwrap_or_else(String::new);
  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `unwrap_or_default()`
 
-error: aborting due to 31 previous errors
+error: aborting due to 32 previous errors