def parse(scanner, rules, scope = ParserScope.empty)
      (rule = rules[rule_name]) && rule.parse(scanner, rules, scope)
    end
def parse(scanner, rules, scope = ParserScope.empty)
      (rule = rules[rule_name]) && rule.parse(scanner, rules, scope)
    end
Apply the parse rule referenced by the #rule_name.

 @param (see Match#parse)

 @return the result of applying the referenced parse rule