add a macro rule open_file!

[electricface]

macro_rules! open_file(
    ($path_str:expr) => (
        ::std::io::File::open(&Path::new( $path_str ))
    );
    ($path_str:expr, rw ) => ( 
        ::std::io::File::open_mode(&Path::new( $path_str ) , ::std::io::Open,
        ::std::io::ReadWrite )
    ); 
    ($path_str:expr, w ) => ( 
        ::std::io::File::open_mode(&Path::new( $path_str ) , ::std::io::Open,
        ::std::io::Write )
    );
    ($path_str:expr, a ) => ( 
        ::std::io::File::open_mode(&Path::new( $path_str ) , ::std::io::Append,
        ::std::io::Write )
    );  
)

example

fn main(){
    let file_path="message.txt";
    let mut file = try_or!(
        open_file!(file_path ,w ),
        "can't open file `{}` : [{}]", file_path,e
        );
}

about macro rule try_or! see #12911

[alexcrichton]

Closing for reasons found here: #12915 (comment)