Method span

packages/compiler/src/expression_parser/parser.ts:654–673

* Retrieve a `ParseSpan` from `start` to the current position (or to `artificialEndIndex` if * provided). * * @param start Position from which the `ParseSpan` will start. * @param artificialEndIndex Optional ending index to be used if provided (and if greater than the * natural en

(start: number, artificialEndIndex?: number)

   *     natural ending index)
   */
  private span(start: number, artificialEndIndex?: number): ParseSpan {
    let endIndex = this.currentEndIndex;
    if (artificialEndIndex !== undefined && artificialEndIndex > this.currentEndIndex) {
      endIndex = artificialEndIndex;
    }

    // In some unusual parsing scenarios (like when certain tokens are missing and an `EmptyExpr` is
    // being created), the current token may already be advanced beyond the `currentEndIndex`. This
    // appears to be a deep-seated parser bug.
    //
    // As a workaround for now, swap the start and end indices to ensure a valid `ParseSpan`.
    // TODO(alxhub): fix the bug upstream in the parser state, and remove this workaround.
    if (start > endIndex) {
      const tmp = endIndex;
      endIndex = start;
      start = tmp;
    }

    return new ParseSpan(start, endIndex);
  }

  private sourceSpan(start: number, artificialEndIndex?: number): AbsoluteSourceSpan {
    const serial = `${start}@${this.inputIndex}:${artificialEndIndex}`;