src/vs/workbench/contrib/search/browser/searchActionsFind.ts/getMultiSelectedSearchResources
function getMultiSelectedSearchResources(viewer: WorkbenchCompressibleObjectTree<RenderableMatch, void>, currElement: RenderableMatch | undefined, sortConfig: ISearchConfigurationProperties): URI[] {
	return getElementsToOperateOnInfo(viewer, currElement, sortConfig).elements
		.map((renderableMatch) => ((renderableMatch instanceof Match) ? null : renderableMatch.resource))
		.filter((renderableMatch): renderableMatch is URI => (renderableMatch !== null));
}