src/vs/editor/contrib/folding/browser/foldingRanges.ts/FoldingRegions/toFoldRange
class FoldingRegions:	public toFoldRange(index: number): FoldRange {
		return <FoldRange>{
			startLineNumber: this._startIndexes[index] & MAX_LINE_NUMBER,
			endLineNumber: this._endIndexes[index] & MAX_LINE_NUMBER,
			type: this._types ? this._types[index] : undefined,
			isCollapsed: this.isCollapsed(index),
			source: this.getSource(index)
		};
	}