Add rust annotation to doctest

seanchen1991 · seanchen1991 · commit aa853bd31775 · 2021-10-27T13:04:42.000-05:00
diff --git a/library/std/src/error.rs b/library/std/src/error.rs
@@ -814,7 +814,7 @@ impl dyn Error + Send + Sync {
 ///
 /// # Examples
 ///
-/// ```
+/// ```rust
 /// #![feature(error_reporter)]
 /// #![feature(negative_impls)]
 ///
