src/vs/editor/common/diff/diffComputer.ts/CharSequence/getEndColumn
class CharSequence:	public getEndColumn(i: number): number {
		if (i === -1) {
			// the end column of the element before the first element
			// is the start column of the first element
			return this.getStartColumn(i + 1);
		}
		this._assertIndex(i, this._columns);

		if (this._charCodes[i] === CharCode.LineFeed) {
			return 1;
		}
		return this._columns[i] + 1;
	}