gistfile1.txt

macro_rules! report_diag (
    ($f: tt, $name: tt, $msg: tt, $(arg: tt)*) => { {
        reg_diag_msg!($name, $msg);                  
        let msg = format!($msg, $($arg)*);
        let msg = format!("{}: {}", stringify!($name), msg);
        $f(msg);
    } };
    ($f: tt, $name: tt, $msg: tt) => { {
        reg_diag_msg!($name, $msg);                    
        let msg = format!("{}: {}", stringify!($name), $msg);
        $f(msg);
    } }
)

macro_rules! alert_err (
    ($sess: expr, $name: tt, $msg: tt, $($arg: tt)*) => (
        report_diag!($sess.err, $name, $msg, $($arg)*);
    );
    ($sess: expr, $name: tt, $msg: tt) => (
        report_diag!($sess.err, $name, $msg);
    )
)

gistfile2.txt

../src/librustc/diag_macros.rs:95:29: 95:30 error: No rules expected the token: .
../src/librustc/diag_macros.rs:95         report_diag!($sess.err, $name, $msg, $($arg)*);
                                                            ^