src/vs/workbench/browser/parts/editor/breadcrumbsPicker.ts/FileIdentityProvider/getId
class FileIdentityProvider:	getId(element: IWorkspace | IWorkspaceFolder | IFileStat | URI): { toString(): string; } {
		if (URI.isUri(element)) {
			return element.toString();
		} else if (isWorkspace(element)) {
			return element.id;
		} else if (isWorkspaceFolder(element)) {
			return element.uri.toString();
		} else {
			return element.resource.toString();
		}
	}