docs/bundle.js
function mountClassInstance(workInProgress, renderExpirationTime) {
    var current = workInProgress.alternate;

    {
      checkClassInstance(workInProgress);
    }

    var instance = workInProgress.stateNode;
    var state = instance.state || null;

    var props = workInProgress.pendingProps;
    !props ? invariant(false, 'There must be pending props for an initial mount. This error is likely caused by a bug in React. Please file an issue.') : void 0;

    var unmaskedContext = getUnmaskedContext(workInProgress);

    instance.props = props;
    instance.state = workInProgress.memoizedState = state;
    instance.refs = emptyObject;
    instance.context = getMaskedContext(workInProgress, unmaskedContext);

    if (enableAsyncSubtreeAPI && workInProgress.type != null && workInProgress.type.prototype != null && workInProgress.type.prototype.unstable_isAsyncReactComponent === true) {
      workInProgress.internalContextTag |= AsyncUpdates;
    }

    if (typeof instance.componentWillMount === 'function') {
      callComponentWillMount(workInProgress, instance);
      // If we had additional state updates during this life-cycle, let's
      // process them now.
      var updateQueue = workInProgress.updateQueue;
      if (updateQueue !== null) {
        instance.state = processUpdateQueue(current, workInProgress, updateQueue, instance, props, renderExpirationTime);
      }
    }
    if (typeof instance.componentDidMount === 'function') {
      workInProgress.effectTag |= Update;
    }
  }
function mountClassInstance(workInProgress, renderExpirationTime) {
    var current = workInProgress.alternate;

    {
      checkClassInstance(workInProgress);
    }

    var instance = workInProgress.stateNode;
    var state = instance.state || null;

    var props = workInProgress.pendingProps;
    !props ? invariant(false, 'There must be pending props for an initial mount. This error is likely caused by a bug in React. Please file an issue.') : void 0;

    var unmaskedContext = getUnmaskedContext(workInProgress);

    instance.props = props;
    instance.state = workInProgress.memoizedState = state;
    instance.refs = emptyObject;
    instance.context = getMaskedContext(workInProgress, unmaskedContext);

    if (enableAsyncSubtreeAPI && workInProgress.type != null && workInProgress.type.prototype != null && workInProgress.type.prototype.unstable_isAsyncReactComponent === true) {
      workInProgress.internalContextTag |= AsyncUpdates;
    }

    if (typeof instance.componentWillMount === 'function') {
      callComponentWillMount(workInProgress, instance);
      // If we had additional state updates during this life-cycle, let's
      // process them now.
      var updateQueue = workInProgress.updateQueue;
      if (updateQueue !== null) {
        instance.state = processUpdateQueue(current, workInProgress, updateQueue, instance, props, renderExpirationTime);
      }
    }
    if (typeof instance.componentDidMount === 'function') {
      workInProgress.effectTag |= Update;
    }
  }
Invokes the mount life-cycles on a previously never rendered instance.