Worked on enhancing Rust compiler diagnostics within the rust-lang/rust repository, specifically targeting the format_args!() macro. Focused on improving error handling and macro development by consolidating diagnostic logic, refining type inference reporting, and adjusting error message ordering to provide clearer feedback during compilation. Addressed a bug related to unhelpful span reporting in type error scenarios, which reduced confusion for developers. Added targeted tests to ensure missing type annotations in format_args!() invocations are properly flagged. Utilized Rust and testing frameworks to deliver these improvements, ultimately streamlining the debugging process and improving the overall developer experience when working with macro formatting issues.