undefined<R> function Null safety

SettableParser<R> undefined<R>(
  1. [String message = 'undefined parser']

Returns a parser that is not defined, but that can be set at a later point in time.

For example, the following code sets up a parser that points to itself and that accepts a sequence of a's ended with the letter b.

final p = undefined();


SettableParser<R> undefined<R>([String message = 'undefined parser']) =>