src/vs/editor/common/model/pieceTreeTextBuffer/pieceTreeBase.ts/PieceTreeBase/getLineLength
class PieceTreeBase:	public getLineLength(lineNumber: number): number {
		if (lineNumber === this.getLineCount()) {
			const startOffset = this.getOffsetAt(lineNumber, 1);
			return this.getLength() - startOffset;
		}
		return this.getOffsetAt(lineNumber + 1, 1) - this.getOffsetAt(lineNumber, 1) - this._EOLLength;
	}