       #
       # @param line [Number] The line number where the invalid directive exists.
       # @param column [Number] The column number where the invalid directive
-      #   exists.
+      # exists.
       # @return [String] A message explaining the validity of the directive.
       #
       invalid: (line, column) ->

  #
  # @param input [Array<String>, String] A list of characters, or a string.
  # @return [String] A string representation of the object passed to the
  #   method.
  #
  @_toString: (input) ->
    return input if toString.call(input) is '[object String]'

  # Statements.
  #
  # @return [Object] An object consisting of functions for handling various
  # types of statement.
  #
  statement: ->
    return {
