@NotNull
  @Override
  public Pair<R, State> parse(@NotNull List<Token<T>> tokens, @NotNull State state) throws ParserException {
    if (myParser != null) {
      return myParser.parse(tokens, state);
    }
    throw new IllegalStateException("Undefined forward parser declaration");
  }
@NotNull
  @Override
  public Pair<R, State> parse(@NotNull List<Token<T>> tokens, @NotNull State state)