Function checkShouldComponentUpdate

code/new-context-api/public/app.js:7633–7658

(workInProgress, oldProps, newProps, oldState, newState, newContext)

  };

  function checkShouldComponentUpdate(workInProgress, oldProps, newProps, oldState, newState, newContext) {
    if (oldProps === null || workInProgress.updateQueue !== null && workInProgress.updateQueue.hasForceUpdate) {
      // If the workInProgress already has an Update effect, return true
      return true;
    }

    var instance = workInProgress.stateNode;
    var ctor = workInProgress.type;
    if (typeof instance.shouldComponentUpdate === 'function') {
      startPhaseTimer(workInProgress, 'shouldComponentUpdate');
      var shouldUpdate = instance.shouldComponentUpdate(newProps, newState, newContext);
      stopPhaseTimer();

      {
        warning(shouldUpdate !== undefined, '%s.shouldComponentUpdate(): Returned undefined instead of a ' + 'boolean value. Make sure to return true or false.', getComponentName(workInProgress) || 'Component');
      }

      return shouldUpdate;
    }

    if (ctor.prototype && ctor.prototype.isPureReactComponent) {
      return !shallowEqual(oldProps, newProps) || !shallowEqual(oldState, newState);
    }

    return true;
  }

  function checkClassInstance(workInProgress) {
    var instance = workInProgress.stateNode;