old-parser/grammar.y

class Query
    rule
        target: expression
                | /* none */ { result = 0 }

          expression: TERM_WITHOUT_QUOTES                                       { result = {:DEFAULT_COLUMN => val[0]} }
          |     TERM_WITH_QUOTES                                                { result = {:DEFAULT_COLUMN => val[0]} }
          |     TERM_WITHOUT_QUOTES COLON TERM_WITHOUT_QUOTES                   { result = {val[0] => val[2]} }
          |     TERM_WITHOUT_QUOTES COLON TERM_WITH_QUOTES                      { result = {val[0] => val[2]} }
end

---- header
  require_relative 'lexer'

---- inner
  def parse(input)
    scan_str(input)
  end