extensions/references-view/src/navigation.ts/Navigation/_anchor
class Navigation:	private _anchor(): undefined | unknown {
		if (!this._delegate) {
			return undefined;
		}
		const [sel] = this._view.selection;
		if (sel) {
			return sel;
		}
		if (!vscode.window.activeTextEditor) {
			return undefined;
		}
		return this._delegate.nearest(vscode.window.activeTextEditor.document.uri, vscode.window.activeTextEditor.selection.active);
	}