code: function advanceTo(newPos) {
  		let n = newPos - pos
  		assert(n >= 0)
  		while (n--) {
  			if (source[pos] === '\n') {
  				column = 1
  				line++
  			} else {
  				column++
  			}
  			pos += 1
  		}
  	}
docs: Advance reading position, updating `pos`, `line` and `column`
  @param {number} newPos - must be greater or equal to current pos