register(view: any) {
   let id = getViewId(view);
   assert(
     'Attempted to register a view with an id already in use: ' + id,
     !this._viewRegistry[id]
   );
   this._viewRegistry[id] = view;
 }

  constructor(
    root: Component | OutletView,
    env: Environment,
    template: OwnedTemplate,
    self: VersionedPathReference<Opaque>,
    parentElement: Simple.Element,
    dynamicScope: DynamicScope,
    builder: IBuilder
  ) {
    assert(`You cannot render \`${self.value()}\` without a template.`, template !== undefined);

    this.id = getViewId(root);
    this.env = env;
    this.root = root;
    this.result = undefined;
    this.shouldReflush = false;
    this.destroyed = false;

    let options = (this.options = {
      alwaysRevalidate: false,
    });

    this.render = () => {
      let layout = template.asLayout();
      let handle = layout.compile();
      let iterator = renderMain(
        layout['compiler'].program,
        env,
        self,
        dynamicScope,
        builder(env, { element: parentElement, nextSibling: null }),
        handle
      );
      let iteratorResult: IteratorResult<RenderResult>;
      do {
        iteratorResult = iterator.next();
      } while (!iteratorResult.done);

      let result = (this.result = iteratorResult.value);

      // override .render function after initial render
      this.render = () => result.rerender(options);
    };
  }

 unregister(view: any) {
   delete this._viewRegistry[getViewId(view)];
 }