Macro abortable_parser::discard

macro_rules! discard {
    ($i:expr, $rule:ident) => { ... };
    ($i:expr, $rule:ident!( $( $args:tt )* ) ) => { ... };
}

Discards the output of a combinator rule when it completes and just returns (). Leaves Failures, Aborts, and Incompletes untouched.