avoid IIFE deoptimization when using const/let inside if branches

src/compiler/parser/html-parser.js

@@ -131,10 +131,10 @@ export function parseHTML (html, options) {
         options.chars(text)
       }
     } else {
-      const stackedTag = lastTag.toLowerCase()
+      var stackedTag = lastTag.toLowerCase()
-      const reStackedTag = reCache[stackedTag] || (reCache[stackedTag] = new RegExp('([\\s\\S]*?)(</' + stackedTag + '[^>]*>)', 'i'))
+      var reStackedTag = reCache[stackedTag] || (reCache[stackedTag] = new RegExp('([\\s\\S]*?)(</' + stackedTag + '[^>]*>)', 'i'))
-      let endTagLength = 0
+      var endTagLength = 0
-      const rest = html.replace(reStackedTag, function (all, text, endTag) {
+      var rest = html.replace(reStackedTag, function (all, text, endTag) {
         endTagLength = endTag.length
         if (stackedTag !== 'script' && stackedTag !== 'style' && stackedTag !== 'noscript') {
           text = text

src/core/util/env.js

@@ -51,9 +51,9 @@ export const nextTick = (function () {
 
   /* istanbul ignore else */
   if (typeof MutationObserver !== 'undefined' && !hasMutationObserverBug) {
-    let counter = 1
+    var counter = 1
-    const observer = new MutationObserver(nextTickHandler)
+    var observer = new MutationObserver(nextTickHandler)
-    const textNode = document.createTextNode(String(counter))
+    var textNode = document.createTextNode(String(counter))
     observer.observe(textNode, {
       characterData: true
     })
@@ -65,7 +65,7 @@ export const nextTick = (function () {
     // webpack attempts to inject a shim for setImmediate
     // if it is used as a global, so we have to work around that to
     // avoid bundling unnecessary code.
-    const context = inBrowser
+    var context = inBrowser
       ? window
       : typeof global !== 'undefined' ? global : {}
     timerFunc = context.setImmediate || setTimeout

src/core/vdom/create-component.js

@@ -57,24 +57,7 @@ export function createComponent (
 
   // functional component
   if (Ctor.options.functional) {
-    const props = {}
+    return createFunctionalComponent(Ctor, propsData, data, context, children)
-    const propOptions = Ctor.options.props
-    if (propOptions) {
-      Object.keys(propOptions).forEach(key => {
-        props[key] = validateProp(key, propOptions, propsData)
-      })
-    }
-    return Ctor.options.render.call(
-      null,
-      context.$createElement,
-      {
-        props,
-        data,
-        parent: context,
-        children: normalizeChildren(children),
-        slots: () => resolveSlots(children)
-      }
-    )
   }
 
   // extract listeners, since these needs to be treated as
@@ -102,6 +85,27 @@ export function createComponent (
   return vnode
 }
 
+function createFunctionalComponent (Ctor, propsData, data, context, children) {
+  const props = {}
+  const propOptions = Ctor.options.props
+  if (propOptions) {
+    for (const key in propOptions) {
+      props[key] = validateProp(key, propOptions, propsData)
+    }
+  }
+  return Ctor.options.render.call(
+    null,
+    context.$createElement,
+    {
+      props,
+      data,
+      parent: context,
+      children: normalizeChildren(children),
+      slots: () => resolveSlots(children)
+    }
+  )
+}
+
 export function createComponentInstanceForVnode (
   vnode: any, // we know it's MountedComponentVNode but flow doesn't
   parent: any // activeInstance in lifecycle state

src/platforms/web/runtime/components/transition-group.js

@@ -120,8 +120,8 @@ export default {
 
     children.forEach(c => {
       if (c.data.moved) {
-        const el = c.elm
+        var el = c.elm
-        const s = el.style
+        var s = el.style
         addTransitionClass(el, moveClass)
         s.transform = s.WebkitTransform = s.transitionDuration = ''
         el._moveDest = c.data.pos

src/platforms/web/runtime/components/transition.js

@@ -141,8 +141,8 @@ export default {
         })
         return placeholder(h, rawChild)
       } else if (mode === 'in-out') {
-        let delayedLeave
+        var delayedLeave
-        const performLeave = () => { delayedLeave() }
+        var performLeave = () => { delayedLeave() }
         mergeVNodeHook(data, 'afterEnter', performLeave)
         mergeVNodeHook(data, 'enterCancelled', performLeave)
         mergeVNodeHook(oldData, 'delayLeave', leave => {

src/platforms/web/runtime/modules/transition.js

@@ -94,7 +94,7 @@ export function enter (vnode: VNodeWithData) {
 
   if (!vnode.data.show) {
     // remove pending leave element on enter by injecting an insert hook
-    const hooks = vnode.data.hook || (vnode.data.hook = {})
+    var hooks = vnode.data.hook || (vnode.data.hook = {})
     hooks._transitionInsert = () => {
       const parent = el.parentNode
       const pendingNode = parent && parent._pending && parent._pending[vnode.key]