further reduce normalizeChildren usage

flow/component.js

@@ -75,7 +75,7 @@ declare interface Component {
     propsData: ?Object,
     listeners: ?{ [key: string]: Function | Array<Function> },
     parentVnode: VNode,
-    renderChildren: ?VNodeChildren
+    renderChildren: ?Array<VNode>
   ) => void;
   // rendering
   _render: () => VNode;

flow/options.js

@@ -4,7 +4,7 @@ declare type InternalComponentOptions = {
   propsData: ?Object;
   _parentVnode: VNode;
   _parentListeners: ?Object;
-  _renderChildren: ?VNodeChildren;
+  _renderChildren: ?Array<VNode>;
   _componentTag: ?string;
   _parentElm: ?Node;
   _refElm: ?Node;
@@ -59,7 +59,7 @@ declare type ComponentOptions = {
   _propKeys?: Array<string>;
   _parentVnode?: VNode;
   _parentListeners?: ?Object;
-  _renderChildren?: ?VNodeChildren;
+  _renderChildren?: ?Array<VNode>;
   _componentTag: ?string;
   _scopeId: ?string;
   _base: Class<Component>;

flow/vnode.js

@@ -4,7 +4,7 @@ declare type VNodeComponentOptions = {
   Ctor: Class<Component>;
   propsData: ?Object;
   listeners: ?Object;
-  children: ?VNodeChildren;
+  children: ?Array<VNode>;
   tag?: string;
 }
 
@@ -19,7 +19,7 @@ declare type MountedComponentVNode = {
 declare type VNodeWithData = {
   tag: string;
   data: VNodeData;
-  children: Array<VNode> | void;
+  children: ?Array<VNode>;
   text: void;
   elm: any;
   ns: string | void;

src/core/instance/lifecycle.js

@@ -117,7 +117,7 @@ export function lifecycleMixin (Vue: Class<Component>) {
     propsData: ?Object,
     listeners: ?Object,
     parentVnode: VNode,
-    renderChildren: ?VNodeChildren
+    renderChildren: ?Array<VNode>
   ) {
     const vm: Component = this
     const hasChildren = !!(vm.$options._renderChildren || renderChildren)

src/core/instance/render.js

@@ -1,7 +1,6 @@
 /* @flow */
 
 import config from '../config'
-import { normalizeChildren } from '../vdom/helpers/index'
 import VNode, {
   cloneVNode,
   cloneVNodes,
@@ -34,7 +33,7 @@ export function initRender (vm: Component) {
   // bind the createElement fn to this instance
   // so that we get proper render context inside it.
   // args order: tag, data, children, needNormalization
-  // the needNormalization flag is flipped and defaults to true for the public version.
+  // the needNormalization flag is disabled for the public version.
   vm._h = (a, b, c, d) => createElement(vm, a, b, c, d, false)
   vm.$createElement = (a, b, c, d) => createElement(vm, a, b, c, d, true)
   if (vm.$options.el) {
@@ -270,14 +269,13 @@ export function renderMixin (Vue: Class<Component>) {
 }
 
 export function resolveSlots (
-  renderChildren: ?VNodeChildren,
+  children: ?Array<VNode>,
   context: ?Component
 ): { [key: string]: Array<VNode> } {
   const slots = {}
-  if (!renderChildren) {
+  if (!children) {
     return slots
   }
-  const children = normalizeChildren(renderChildren) || []
   const defaultSlot = []
   let name, child
   for (let i = 0, l = children.length; i < l; i++) {

src/core/vdom/create-component.js

@@ -1,7 +1,6 @@
 /* @flow */
 
 import VNode from './vnode'
-import { normalizeChildren } from './helpers/index'
 import { resolveConstructorOptions } from '../instance/init'
 import { activeInstance, callHook } from '../instance/lifecycle'
 import { resolveSlots } from '../instance/render'
@@ -15,7 +14,7 @@ export function createComponent (
   Ctor: Class<Component> | Function | Object | void,
   data?: VNodeData,
   context: Component,
-  children?: VNodeChildren,
+  children: ?Array<VNode>,
   tag?: string
 ): VNode | void {
   if (!Ctor) {
@@ -96,7 +95,7 @@ function createFunctionalComponent (
   propsData: ?Object,
   data: VNodeData,
   context: Component,
-  children?: VNodeChildren
+  children: ?Array<VNode>
 ): VNode | void {
   const props = {}
   const propOptions = Ctor.options.props
@@ -113,7 +112,7 @@ function createFunctionalComponent (
     props,
     data,
     parent: context,
-    children: normalizeChildren(children),
+    children,
     slots: () => resolveSlots(children, context)
   })
   if (vnode instanceof VNode) {

src/core/vdom/create-element.js

@@ -14,14 +14,14 @@ export function createElement (
   data: any,
   children: any,
   needNormalization: any,
-  flipNormalization: boolean
+  alwaysNormalize: boolean
 ): VNode {
   if (Array.isArray(data) || isPrimitive(data)) {
     needNormalization = children
     children = data
     data = undefined
   }
-  if (flipNormalization) needNormalization = !needNormalization
+  if (alwaysNormalize) needNormalization = true
   return _createElement(context, tag, data, children, needNormalization)
 }
 
@@ -51,6 +51,9 @@ export function _createElement (
     data.scopedSlots = { default: children[0] }
     children.length = 0
   }
+  if (needNormalization) {
+    children = normalizeChildren(children)
+  }
   let vnode, ns
   if (typeof tag === 'string') {
     let Ctor
@@ -58,7 +61,7 @@ export function _createElement (
     if (config.isReservedTag(tag)) {
       // platform built-in elements
       vnode = new VNode(
-        tag, data, needNormalization ? normalizeChildren(children) : children,
+        tag, data, children,
         undefined, undefined, context
       )
     } else if ((Ctor = resolveAsset(context.$options, 'components', tag))) {
@@ -70,7 +73,7 @@ export function _createElement (
       // parent normalizes children
       ns = tag === 'foreignObject' ? 'xhtml' : ns
       vnode = new VNode(
-        tag, data, needNormalization ? normalizeChildren(children) : children,
+        tag, data, children,
         undefined, undefined, context
       )
     }

src/core/vdom/helpers/normalize-children.js

@@ -3,7 +3,7 @@
 import { isPrimitive } from 'core/util/index'
 import VNode, { createTextVNode } from 'core/vdom/vnode'
 
-export function normalizeChildren (children: any): Array<VNode> | void {
+export function normalizeChildren (children: any): ?Array<VNode> {
   return isPrimitive(children)
     ? [createTextVNode(children)]
     : Array.isArray(children)

src/core/vdom/vnode.js

@@ -3,7 +3,7 @@
 export default class VNode {
   tag: string | void;
   data: VNodeData | void;
-  children: Array<VNode> | void;
+  children: ?Array<VNode>;
   text: string | void;
   elm: Node | void;
   ns: string | void;
@@ -23,7 +23,7 @@ export default class VNode {
   constructor (
     tag?: string,
     data?: VNodeData,
-    children?: Array<VNode> | void,
+    children?: ?Array<VNode>,
     text?: string,
     elm?: Node,
     context?: Component,