STRING_ADD example

Author: alex-semenyuk

clippy_lints/src/strings.rs

@@ -63,7 +63,7 @@ declare_clippy_lint! {
     ///
     /// Use instead:
     /// ```rust
-    /// let x = "Hello".to_owned();
+    /// let mut x = "Hello".to_owned();
     /// x.push_str(", World");
     /// ```
     #[clippy::version = "pre 1.29.0"]