code: function enterView(newView, host) {
      var oldView = viewData;
      directives = newView && newView[DIRECTIVES];
      tView = newView && newView[TVIEW];
      creationMode = newView && (newView[FLAGS] & 1 /* CreationMode */) === 1 /* CreationMode */;
      firstTemplatePass = newView && tView.firstTemplatePass;
      renderer = newView && newView[RENDERER];
      if (host != null) {
          previousOrParentNode = host;
          isParent = true;
      }
      viewData = newView;
      currentQueries = newView && newView[QUERIES];
      return oldView;
  }
docs: Swap the current state with a new state.
  
  For performance reasons we store the state in the top level of the module.
  This way we minimize the number of properties to read. Whenever a new view
  is entered we have to store the state for later, and when the view is
  exited the state has to be restored
  
  @param newView New state to become active
  @param host Element to which the View is a child of
  @returns the previous state;