Macro trashcan::chain

macro_rules! chain {
    ($input:expr, $parser:expr) => { ... };
    ($input:expr, $parser:expr => $($rest:tt)*) => { ... };
    ($orig:expr; $input:expr, $parser:expr) => { ... };
    ($orig:expr; $input:expr, $parser:expr => $($rest:tt)*) => { ... };
}