Add #[must_use] annotation to Result::ok

Author: yotamofek

library/core/src/result.rs

@@ -655,6 +655,7 @@ impl<T, E> Result<T, E> {
     #[inline]
     #[stable(feature = "rust1", since = "1.0.0")]
     #[rustc_diagnostic_item = "result_ok_method"]
+    #[must_use]
     pub fn ok(self) -> Option<T> {
         match self {
             Ok(x) => Some(x),

library/std/src/panicking.rs

@@ -322,7 +322,7 @@ fn default_hook(info: &PanicHookInfo<'_>) {
 
     if let Ok(Some(local)) = try_set_output_capture(None) {
         write(&mut *local.lock().unwrap_or_else(|e| e.into_inner()));
-        try_set_output_capture(Some(local)).ok();
+        let _ = try_set_output_capture(Some(local));
     } else if let Some(mut out) = panic_output() {
         write(&mut out);
     }