src/vs/editor/contrib/folding/browser/foldingRanges.ts/FoldingRegions/getSource
class FoldingRegions:	public getSource(index: number): FoldSource {
		if (this.isUserDefined(index)) {
			return FoldSource.userDefined;
		} else if (this.isRecovered(index)) {
			return FoldSource.recovered;
		}
		return FoldSource.provider;
	}