src/vs/editor/contrib/gotoSymbol/browser/peek/referencesWidget.ts/ReferenceWidget/_getFocusedReference
class ReferenceWidget:	private _getFocusedReference(): OneReference | undefined {
		const [element] = this._tree.getFocus();
		if (element instanceof OneReference) {
			return element;
		} else if (element instanceof FileReferences) {
			if (element.children.length > 0) {
				return element.children[0];
			}
		}
		return undefined;
	}