error: `to_string()` called on a `String`
  --> $DIR/string_to_string.rs:6:17
   |
LL |     let mut v = message.to_string();
   |                 ^^^^^^^^^^^^^^^^^^^
   |
   = note: `-D clippy::string-to-string` implied by `-D warnings`
   = help: consider using `.clone()`

error: aborting due to previous error