Method scanNumber

packages/compiler/src/expression_parser/lexer.ts:466–505

(start: number)

  }

  private scanNumber(start: number): Token {
    let simple = this.index === start;
    let hasSeparators = false;
    this.advance(); // Skip initial digit.
    while (true) {
      if (chars.isDigit(this.peek)) {
        // Do nothing.
      } else if (this.peek === chars.$_) {
        // Separators are only valid when they're surrounded by digits. E.g. `1_0_1` is
        // valid while `_101` and `101_` are not. The separator can't be next to the decimal
        // point or another separator either. Note that it's unlikely that we'll hit a case where
        // the underscore is at the start, because that's a valid identifier and it will be picked
        // up earlier in the parsing. We validate for it anyway just in case.
        if (
          !chars.isDigit(this.input.charCodeAt(this.index - 1)) ||
          !chars.isDigit(this.input.charCodeAt(this.index + 1))
        ) {
          return this.error('Invalid numeric separator', 0);
        }
        hasSeparators = true;
      } else if (this.peek === chars.$PERIOD) {
        simple = false;
      } else if (isExponentStart(this.peek)) {
        this.advance();
        if (isExponentSign(this.peek)) this.advance();
        if (!chars.isDigit(this.peek)) return this.error('Invalid exponent', -1);
        simple = false;
      } else {
        break;
      }
      this.advance();
    }

    let str = this.input.substring(start, this.index);
    if (hasSeparators) {
      str = str.replace(/_/g, '');
    }
    const value = simple ? parseIntAutoRadix(str) : parseFloat(str);
    return newNumberToken(start, this.index, value);
  }

  private scanString(): Token {
    const start = this.index;