new Vue({
 el: '#app'
})

import { initMixin } from './init'
import { stateMixin } from './state'
import { renderMixin } from './render'
import { eventsMixin } from './events'
import { lifecycleMixin } from './lifecycle'
import { warn } from '../util/index'
function Vue (options) {
 if (process.env.NODE_ENV !== 'production' &&
 !(this instanceof Vue)
 ) {
 warn('Vue is a constructor and should be called with the `new` keyword')
 }
 this._init(options)
}
initMixin(Vue)
stateMixin(Vue)
eventsMixin(Vue)
lifecycleMixin(Vue)
renderMixin(Vue)
export default Vue

export function initMixin (Vue: Class<Component>) {
 Vue.prototype._init = function (options?: Object) {
 const vm: Component = this
 // a uid
 vm._uid = uid++
 let startTag, endTag
 /* istanbul ignore if */
 if (process.env.NODE_ENV !== 'production' && config.performance && mark) {
 startTag = `vue-perf-start:${vm._uid}`
 endTag = `vue-perf-end:${vm._uid}`
 mark(startTag)
 }
 // a flag to avoid this being observed
 vm._isVue = true
 // merge options
 if (options && options._isComponent) {
 // optimize internal component instantiation
 // since dynamic options merging is pretty slow, and none of the
 // internal component options needs special treatment.
 initInternalComponent(vm, options)
 } else {
 vm.$options = mergeOptions(
 resolveConstructorOptions(vm.constructor),
 options || {},
 vm
 )
 }
 /* istanbul ignore else */
 if (process.env.NODE_ENV !== 'production') {
 initProxy(vm)
 } else {
 vm._renderProxy = vm
 }
 // expose real self
 vm._self = vm
 initLifecycle(vm)
 initEvents(vm)
 initRender(vm)
 callHook(vm, 'beforeCreate')
 initInjections(vm) // resolve injections before data/props
 initState(vm)
 initProvide(vm) // resolve provide after data/props
 callHook(vm, 'created')
 /* istanbul ignore if */
 if (process.env.NODE_ENV !== 'production' && config.performance && mark) {
 vm._name = formatComponentName(vm, false)
 mark(endTag)
 measure(`vue ${vm._name} init`, startTag, endTag)
 }
 if (vm.$options.el) {
 vm.$mount(vm.$options.el)
 }
 }
}

...
 initLifecycle(vm)
 initEvents(vm)
 initRender(vm)
 callHook(vm, 'beforeCreate')
 initInjections(vm) // resolve injections before data/props
 initState(vm)
 initProvide(vm) // resolve provide after data/props
 callHook(vm, 'created')
...
if (vm.$options.el) {
 vm.$mount(vm.$options.el)
}
...

export function initLifecycle (vm: Component) {
 const options = vm.$options
 // locate first non-abstract parent
 let parent = options.parent
 if (parent && !options.abstract) {
 while (parent.$options.abstract && parent.$parent) {
 parent = parent.$parent
 }
 parent.$children.push(vm)
 }
 vm.$parent = parent
 vm.$root = parent ? parent.$root : vm
 vm.$children = []
 vm.$refs = {}
 vm._watcher = null
 vm._inactive = null
 vm._directInactive = false
 vm._isMounted = false
 vm._isDestroyed = false
 vm._isBeingDestroyed = false
}

export function initState (vm: Component) {
 vm._watchers = []
 const opts = vm.$options
 if (opts.props) initProps(vm, opts.props)
 if (opts.methods) initMethods(vm, opts.methods)
 if (opts.data) {
 initData(vm)
 } else {
 observe(vm._data = {}, true /* asRootData */)
 }
 if (opts.computed) initComputed(vm, opts.computed)
 if (opts.watch && opts.watch !== nativeWatch) {
 initWatch(vm, opts.watch)
 }
}

function initData (vm: Component) {
 let data = vm.$options.data
 data = vm._data = typeof data === 'function'
 ? getData(data, vm)
 : data || {}
 if (!isPlainObject(data)) {
 data = {}
 process.env.NODE_ENV !== 'production' && warn(
 'data functions should return an object:\n' +
 'https://vuejs.org/v2/guide/components.html#data-Must-Be-a-Function',
 vm
 )
 }
 // proxy data on instance
 const keys = Object.keys(data)
 const props = vm.$options.props
 const methods = vm.$options.methods
 let i = keys.length
 while (i--) {
 const key = keys[i]
 if (process.env.NODE_ENV !== 'production') {
 if (methods && hasOwn(methods, key)) {
 warn(
 `Method "${key}" has already been defined as a data property.`,
 vm
 )
 }
 }
 if (props && hasOwn(props, key)) {
 process.env.NODE_ENV !== 'production' && warn(
 `The data property "${key}" is already declared as a prop. ` +
 `Use prop default value instead.`,
 vm
 )
 } else if (!isReserved(key)) {
 proxy(vm, `_data`, key)
 }
 }
 // observe data
 observe(data, true /* asRootData */)
}

export function observe (value: any, asRootData: ?boolean): Observer | void {
 if (!isObject(value) || value instanceof VNode) {
 return
 }
 let ob: Observer | void
 if (hasOwn(value, '__ob__') && value.__ob__ instanceof Observer) {
 ob = value.__ob__
 } else if (
 shouldObserve &&
 !isServerRendering() &&
 (Array.isArray(value) || isPlainObject(value)) &&
 Object.isExtensible(value) &&
 !value._isVue
 ) {
 ob = new Observer(value)
 }
 if (asRootData && ob) {
 ob.vmCount++
 }
 return ob
}

export class Observer {
 value: any;
 dep: Dep;
 vmCount: number; // number of vms that have this object as root $data
 constructor (value: any) {
 this.value = value
 this.dep = new Dep()
 this.vmCount = 0
 def(value, '__ob__', this)
 if (Array.isArray(value)) {
 if (hasProto) {
 protoAugment(value, arrayMethods)
 } else {
 copyAugment(value, arrayMethods, arrayKeys)
 }
 this.observeArray(value)
 } else {
 this.walk(value)
 }
 }
 /**
 * Walk through all properties and convert them into
 * getter/setters. This method should only be called when
 * value type is Object.
 */
 walk (obj: Object) {
 const keys = Object.keys(obj)
 for (let i = 0; i < keys.length; i++) {
 defineReactive(obj, keys[i])
 }
 }
 /**
 * Observe a list of Array items.
 */
 observeArray (items: Array<any>) {
 for (let i = 0, l = items.length; i < l; i++) {
 observe(items[i])
 }
 }
}

export function defineReactive (
 obj: Object,
 key: string,
 val: any,
 customSetter?: ?Function,
 shallow?: boolean
) {
 const dep = new Dep()
 const property = Object.getOwnPropertyDescriptor(obj, key)
 if (property && property.configurable === false) {
 return
 }
 // cater for pre-defined getter/setters
 const getter = property && property.get
 const setter = property && property.set
 if ((!getter || setter) && arguments.length === 2) {
 val = obj[key]
 }
 let childOb = !shallow && observe(val)
 Object.defineProperty(obj, key, {
 enumerable: true,
 configurable: true,
 get: function reactiveGetter () {
 const value = getter ? getter.call(obj) : val
 if (Dep.target) {
 dep.depend()
 if (childOb) {
 childOb.dep.depend()
 if (Array.isArray(value)) {
 dependArray(value)
 }
 }
 }
 return value
 },
 set: function reactiveSetter (newVal) {
 const value = getter ? getter.call(obj) : val
 /* eslint-disable no-self-compare */
 if (newVal === value || (newVal !== newVal && value !== value)) {
 return
 }
 /* eslint-enable no-self-compare */
 if (process.env.NODE_ENV !== 'production' && customSetter) {
 customSetter()
 }
 // #7981: for accessor properties without setter
 if (getter && !setter) return
 if (setter) {
 setter.call(obj, newVal)
 } else {
 val = newVal
 }
 childOb = !shallow && observe(newVal)
 dep.notify()
 }
 })
}

export default class Dep {
 static target: ?Watcher;
 id: number;
 subs: Array<Watcher>;
 constructor () {
 this.id = uid++
 this.subs = []
 }
 addSub (sub: Watcher) {
 this.subs.push(sub)
 }
 removeSub (sub: Watcher) {
 remove(this.subs, sub)
 }
 depend () {
 if (Dep.target) {
 Dep.target.addDep(this)
 }
 }
 notify () {
 // stabilize the subscriber list first
 const subs = this.subs.slice()
 if (process.env.NODE_ENV !== 'production' && !config.async) {
 // subs aren't sorted in scheduler if not running async
 // we need to sort them now to make sure they fire in correct
 // order
 subs.sort((a, b) => a.id - b.id)
 }
 for (let i = 0, l = subs.length; i < l; i++) {
 subs[i].update()
 }
 }
}
// The current target watcher being evaluated.
// This is globally unique because only one watcher
// can be evaluated at a time.
Dep.target = null
const targetStack = []
export function pushTarget (target: ?Watcher) {
 targetStack.push(target)
 Dep.target = target
}
export function popTarget () {
 targetStack.pop()
 Dep.target = targetStack[targetStack.length - 1]
}

export default class Watcher {
 vm: Component;
 expression: string;
 cb: Function;
 id: number;
 deep: boolean;
 user: boolean;
 lazy: boolean;
 sync: boolean;
 dirty: boolean;
 active: boolean;
 deps: Array<Dep>;
 newDeps: Array<Dep>;
 depIds: SimpleSet;
 newDepIds: SimpleSet;
 before: ?Function;
 getter: Function;
 value: any;
 constructor (
 vm: Component,
 expOrFn: string | Function,
 cb: Function,
 options?: ?Object,
 isRenderWatcher?: boolean
 ) {
 this.vm = vm
 if (isRenderWatcher) {
 vm._watcher = this
 }
 vm._watchers.push(this)
 // options
 if (options) {
 this.deep = !!options.deep
 this.user = !!options.user
 this.lazy = !!options.lazy
 this.sync = !!options.sync
 this.before = options.before
 } else {
 this.deep = this.user = this.lazy = this.sync = false
 }
 this.cb = cb
 this.id = ++uid // uid for batching
 this.active = true
 this.dirty = this.lazy // for lazy watchers
 this.deps = []
 this.newDeps = []
 this.depIds = new Set()
 this.newDepIds = new Set()
 this.expression = process.env.NODE_ENV !== 'production'
 ? expOrFn.toString()
 : ''
 // parse expression for getter
 if (typeof expOrFn === 'function') {
 this.getter = expOrFn
 } else {
 this.getter = parsePath(expOrFn)
 if (!this.getter) {
 this.getter = noop
 process.env.NODE_ENV !== 'production' && warn(
 `Failed watching path: "${expOrFn}" ` +
 'Watcher only accepts simple dot-delimited paths. ' +
 'For full control, use a function instead.',
 vm
 )
 }
 }
 this.value = this.lazy
 ? undefined
 : this.get()
 }
 /**
 * Evaluate the getter, and re-collect dependencies.
 */
 get () {
 pushTarget(this)
 let value
 const vm = this.vm
 try {
 value = this.getter.call(vm, vm)
 } catch (e) {
 if (this.user) {
 handleError(e, vm, `getter for watcher "${this.expression}"`)
 } else {
 throw e
 }
 } finally {
 // "touch" every property so they are all tracked as
 // dependencies for deep watching
 if (this.deep) {
 traverse(value)
 }
 popTarget()
 this.cleanupDeps()
 }
 return value
 }
 /**
 * Add a dependency to this directive.
 */
 addDep (dep: Dep) {
 const id = dep.id
 if (!this.newDepIds.has(id)) {
 this.newDepIds.add(id)
 this.newDeps.push(dep)
 if (!this.depIds.has(id)) {
 dep.addSub(this)
 }
 }
 }
 /**
 * Clean up for dependency collection.
 */
 cleanupDeps () {
 let i = this.deps.length
 while (i--) {
 const dep = this.deps[i]
 if (!this.newDepIds.has(dep.id)) {
 dep.removeSub(this)
 }
 }
 let tmp = this.depIds
 this.depIds = this.newDepIds
 this.newDepIds = tmp
 this.newDepIds.clear()
 tmp = this.deps
 this.deps = this.newDeps
 this.newDeps = tmp
 this.newDeps.length = 0
 }
 /**
 * Subscriber interface.
 * Will be called when a dependency changes.
 */
 update () {
 /* istanbul ignore else */
 if (this.lazy) {
 this.dirty = true
 } else if (this.sync) {
 this.run()
 } else {
 queueWatcher(this)
 }
 }
 /**
 * Scheduler job interface.
 * Will be called by the scheduler.
 */
 run () {
 if (this.active) {
 const value = this.get()
 if (
 value !== this.value ||
 // Deep watchers and watchers on Object/Arrays should fire even
 // when the value is the same, because the value may
 // have mutated.
 isObject(value) ||
 this.deep
 ) {
 // set new value
 const oldValue = this.value
 this.value = value
 if (this.user) {
 try {
 this.cb.call(this.vm, value, oldValue)
 } catch (e) {
 handleError(e, this.vm, `callback for watcher "${this.expression}"`)
 }
 } else {
 this.cb.call(this.vm, value, oldValue)
 }
 }
 }
 }
 /**
 * Evaluate the value of the watcher.
 * This only gets called for lazy watchers.
 */
 evaluate () {
 this.value = this.get()
 this.dirty = false
 }
 /**
 * Depend on all deps collected by this watcher.
 */
 depend () {
 let i = this.deps.length
 while (i--) {
 this.deps[i].depend()
 }
 }
 /**
 * Remove self from all dependencies' subscriber list.
 */
 teardown () {
 if (this.active) {
 // remove self from vm's watcher list
 // this is a somewhat expensive operation so we skip it
 // if the vm is being destroyed.
 if (!this.vm._isBeingDestroyed) {
 remove(this.vm._watchers, this)
 }
 let i = this.deps.length
 while (i--) {
 this.deps[i].removeSub(this)
 }
 this.active = false
 }
 }
}