std::macros::writeln

macro_rules! writeln(
    ($dst:expr, $($arg:tt)*) => ({
        let dst: &mut ::std::io::Writer = $dst;
        format_args!(|args| { ::std::fmt::writeln(dst, args) }, $($arg)*)
    })
)

Equivalent to the write! macro, except that a newline is appended after the message is written.