Macro combine::dispatch_parser_impl

macro_rules! dispatch_parser_impl {
    ($parser_name: ident [$first_ident: ident $($id: ident)*] [$($collected_idents: ident)*] $expr: expr, $($rest: expr,)*) => { ... };
    ($parser_name: ident [$($id: ident)*] [$($collected_idents: ident)*]) => { ... };
    ($parser_name: ident; $($id: ident)*) => { ... };
}