src/vs/editor/common/diff/algorithms/myersDiffAlgorithm.ts/FastArrayNegativeIndices/set
class FastArrayNegativeIndices:	set(idx: number, value: T): void {
		if (idx < 0) {
			idx = -idx - 1;
			this.negativeArr[idx] = value;
		} else {
			this.positiveArr[idx] = value;
		}
	}