src/vs/editor/contrib/folding/browser/foldingRanges.ts/FoldingRegions/setSource
class FoldingRegions:	public setSource(index: number, source: FoldSource): void {
		if (source === FoldSource.userDefined) {
			this.setUserDefined(index, true);
			this.setRecovered(index, false);
		} else if (source === FoldSource.recovered) {
			this.setUserDefined(index, false);
			this.setRecovered(index, true);
		} else {
			this.setUserDefined(index, false);
			this.setRecovered(index, false);
		}
	}