error: invalid format string: unmatched `}` found --> $DIR/format-concat-span.rs:13:13 | LL | format!(concat!("abc}")); | ^^^^^^^^^^^^^^^ unmatched `}` in format string | = note: if you intended to print `}`, you can escape it using `}}` = note: this error originates in the macro `concat` (in Nightly builds, run with -Z macro-backtrace for more info) error: aborting due to previous error