rust-clippy/tests/ui/format_push_string.stderr

error: `format!(..)` appended to existing `String`
  --> $DIR/format_push_string.rs:5:5
   |
LL |     string += &format!("{:?}", 1234);
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = help: consider using `write!` to avoid the extra allocation
   = note: `-D clippy::format-push-string` implied by `-D warnings`

error: `format!(..)` appended to existing `String`
  --> $DIR/format_push_string.rs:6:5
   |
LL |     string.push_str(&format!("{:?}", 5678));
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = help: consider using `write!` to avoid the extra allocation

error: aborting due to 2 previous errors