error: `format!(..)` appended to existing `String`
  --> tests/ui/format_push_string_no_std.rs:13:5
   |
LL |     string.push_str(&format!("{:?}", 1234));
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = note: you may need to import the `core::fmt::Write` trait
   = note: `-D clippy::format-push-string` implied by `-D warnings`
   = help: to override `-D warnings` add `#[allow(clippy::format_push_string)]`
help: consider using `write!` to avoid the extra allocation
   |
LL -     string.push_str(&format!("{:?}", 1234));
LL +     let _ = write!(string, "{:?}", 1234);
   |

error: aborting due to 1 previous error