anchor.diff:            } else if (_lookingAtInterpolatedIdentifier()) {
               addSingleExpression(_identifierLike());
             } else {
  +            scanner.readChar();
               addOperator(BinaryOperator.minus);
             }
             break;
  
positive.code: 
        var decimal = 0.1;
        while (isDigit(scanner.peekChar())) {
          number += (scanner.readChar() - $0) * decimal;
          decimal /= 10;
        }
      }
  
negative.code: 
      while (isDigit(scanner.peekChar())) {
        number *= 10;
        number += asDecimal(scanner.readChar());
      }
  
      if (scanner.peekChar() == $dot) {
  