diff --git a/packages/core/__tests__/attrsFallthrough.spec.ts b/packages/core/__tests__/attrsFallthrough.spec.ts
index c10adb2b..a6df61ce 100644
--- a/packages/core/__tests__/attrsFallthrough.spec.ts
+++ b/packages/core/__tests__/attrsFallthrough.spec.ts
@@ -6,9 +6,7 @@ describe('attribute fallthrough', () => {
     const nativeClick = jest.fn()
     const childUpdated = jest.fn()
 
-    class Hello extends Component<{
-      count: number
-    }> {
+    class Hello extends Component<{}, { count: number }> {
       data() {
         return {
           count: 0
@@ -29,7 +27,7 @@ describe('attribute fallthrough', () => {
       }
     }
 
-    class Child extends Component<{}, { foo: number }> {
+    class Child extends Component<{ foo: number }> {
       updated() {
         childUpdated()
       }
@@ -75,7 +73,7 @@ describe('attribute fallthrough', () => {
     const nativeClick = jest.fn()
     const childUpdated = jest.fn()
 
-    class Hello extends Component<{ count: number }> {
+    class Hello extends Component<{}, { count: number }> {
       data() {
         return {
           count: 0
@@ -96,7 +94,7 @@ describe('attribute fallthrough', () => {
       }
     }
 
-    class Child extends Component<{}, { foo: number }> {
+    class Child extends Component<{ foo: number }> {
       static options = {
         props: {
           foo: Number
@@ -149,7 +147,7 @@ describe('attribute fallthrough', () => {
     const childUpdated = jest.fn()
     const grandChildUpdated = jest.fn()
 
-    class Hello extends Component<{ count: number }> {
+    class Hello extends Component<{}, { count: number }> {
       data() {
         return {
           count: 0
@@ -184,7 +182,7 @@ describe('attribute fallthrough', () => {
       }
     }
 
-    class GrandChild extends Component<{}, { foo: number }> {
+    class GrandChild extends Component<{ foo: number }> {
       static options = {
         props: {
           foo: Number
diff --git a/packages/core/src/component.ts b/packages/core/src/component.ts
index eb35be4d..556ae9b2 100644
--- a/packages/core/src/component.ts
+++ b/packages/core/src/component.ts
@@ -13,42 +13,40 @@ import { ErrorTypes } from './errorHandling'
 
 type Flatten<T> = { [K in keyof T]: T[K] }
 
-export type RenderFunction<P = {}> = (
-  props: P,
-  slots: Slots,
-  attrs: Data
-) => any
-
 export interface ComponentClass extends Flatten<typeof InternalComponent> {
-  new <D = {}, P = {}>(): D & P & MountedComponent<D, P>
+  new <P extends object = {}, D extends object = {}>(): MergedComponent<P, D>
 }
 
-export interface FunctionalComponent<P = {}> extends RenderFunction<P> {
+export type MergedComponent<P, D> = D & P & MountedComponent<P, D>
+
+export interface FunctionalComponent<P = {}> {
+  (props: Readonly<P>, slots: Slots, attrs: Data): any
   pure?: boolean
   props?: ComponentPropsOptions<P>
   inheritAttrs?: boolean
+  displayName?: string
 }
 
 export type ComponentType = ComponentClass | FunctionalComponent
 
 // this interface is merged with the class type
 // to represent a mounted component
-export interface MountedComponent<D = {}, P = {}> extends InternalComponent {
+export interface MountedComponent<P = {}, D = {}> extends InternalComponent {
   $vnode: MountedVNode
   $data: D
-  $props: P
+  $props: Readonly<P>
   $attrs: Data
   $computed: Data
   $slots: Slots
   $root: MountedComponent
   $children: MountedComponent[]
-  $options: ComponentOptions<D, P>
+  $options: ComponentOptions<P, D>
 
-  render(props: P, slots: Slots, attrs: Data): any
+  data?(): Partial<D>
+  render(props: Readonly<P>, slots: Slots, attrs: Data): any
   renderError?(e: Error): any
   renderTracked?(e: DebuggerEvent): void
   renderTriggered?(e: DebuggerEvent): void
-  data?(): Partial<D>
   beforeCreate?(): void
   created?(): void
   beforeMount?(): void
@@ -120,16 +118,15 @@ class InternalComponent {
   }
 
   $watch(
-    this: MountedComponent,
     keyOrFn: string | (() => any),
     cb: (newValue: any, oldValue: any) => void,
     options?: WatchOptions
   ) {
-    return setupWatcher(this, keyOrFn, cb, options)
+    return setupWatcher(this as any, keyOrFn, cb, options)
   }
 
   // eventEmitter interface
-  $on(this: MountedComponent, event: string, fn: Function): MountedComponent {
+  $on(event: string, fn: Function): this {
     if (Array.isArray(event)) {
       for (let i = 0; i < event.length; i++) {
         this.$on(event[i], fn)
@@ -141,7 +138,7 @@ class InternalComponent {
     return this
   }
 
-  $once(this: MountedComponent, event: string, fn: Function): MountedComponent {
+  $once(event: string, fn: Function): this {
     const onceFn = (...args: any[]) => {
       this.$off(event, onceFn)
       fn.apply(this, args)
@@ -150,11 +147,7 @@ class InternalComponent {
     return this.$on(event, onceFn)
   }
 
-  $off(
-    this: MountedComponent,
-    event?: string,
-    fn?: Function
-  ): MountedComponent {
+  $off(event?: string, fn?: Function): this {
     if (this._events) {
       if (!event && !fn) {
         this._events = null
@@ -180,11 +173,7 @@ class InternalComponent {
     return this
   }
 
-  $emit(
-    this: MountedComponent,
-    name: string,
-    ...payload: any[]
-  ): MountedComponent {
+  $emit(name: string, ...payload: any[]): this {
     const parentData =
       (this.$parentVNode && this.$parentVNode.data) || EMPTY_OBJ
     const parentListener =
diff --git a/packages/core/src/componentOptions.ts b/packages/core/src/componentOptions.ts
index 5723d10e..ab8c5194 100644
--- a/packages/core/src/componentOptions.ts
+++ b/packages/core/src/componentOptions.ts
@@ -1,14 +1,22 @@
-import { MountedComponent, RenderFunction } from './component'
+import { MergedComponent, MountedComponent } from './component'
+import { Slots } from './vdom'
 
 export type Data = Record<string, any>
 
-export interface ComponentOptions<D = Data, P = Data> {
-  data?: () => Partial<D>
+export interface ComponentOptions<
+  P = {},
+  D = {},
+  M = {},
+  C = {},
+  This = MergedComponent<P, D> & M & C
+> {
+  data?: (this: This) => Partial<D>
   props?: ComponentPropsOptions<P>
-  computed?: ComponentComputedOptions<D, P>
-  watch?: ComponentWatchOptions<D, P>
-  render?: RenderFunction<P>
+  computed?: ComponentComputedOptions<This>
+  watch?: ComponentWatchOptions<This>
+  render?: (this: This, props: Readonly<P>, slots: Slots, attrs: Data) => any
   inheritAttrs?: boolean
+  displayName?: string
   // TODO other options
   readonly [key: string]: any
 }
@@ -30,24 +38,28 @@ export interface PropOptions<T = any> {
   validator?(value: T): boolean
 }
 
-export interface ComponentComputedOptions<D = Data, P = Data> {
-  [key: string]: (this: MountedComponent<D, P> & D & P, c: any) => any
+export interface ComponentComputedOptions<This = MountedComponent> {
+  [key: string]: (this: This, c: any) => any
 }
 
-export interface ComponentWatchOptions<D = Data, P = Data> {
-  [key: string]: ComponentWatchOption<MountedComponent<D, P> & D & P>
+export interface ComponentWatchOptions<This = MountedComponent> {
+  [key: string]: ComponentWatchOption<This>
 }
 
-export type ComponentWatchOption<C = any> =
-  | WatchHandler<C>
-  | WatchHandler<C>[]
-  | WatchOptionsWithHandler<C>
+export type ComponentWatchOption<This = MountedComponent> =
+  | WatchHandler<This>
+  | WatchHandler<This>[]
+  | WatchOptionsWithHandler<This>
   | string
 
-export type WatchHandler<C = any> = (this: C, val: any, oldVal: any) => void
+export type WatchHandler<This = any> = (
+  this: This,
+  val: any,
+  oldVal: any
+) => void
 
-export interface WatchOptionsWithHandler<C = any> extends WatchOptions {
-  handler: WatchHandler<C>
+export interface WatchOptionsWithHandler<This = any> extends WatchOptions {
+  handler: WatchHandler<This>
 }
 
 export interface WatchOptions {
diff --git a/packages/core/src/optional/asyncComponent.ts b/packages/core/src/optional/asyncComponent.ts
index 1a60b49e..5b5a2c70 100644
--- a/packages/core/src/optional/asyncComponent.ts
+++ b/packages/core/src/optional/asyncComponent.ts
@@ -40,7 +40,7 @@ export function createAsyncComponent(
     error: errorComp
   } = options
 
-  return class AsyncContainer extends Component<AsyncContainerData> {
+  return class AsyncContainer extends Component<{}, AsyncContainerData> {
     data() {
       return {
         comp: null,
diff --git a/packages/core/src/optional/context.ts b/packages/core/src/optional/context.ts
index f8d688d5..a260370d 100644
--- a/packages/core/src/optional/context.ts
+++ b/packages/core/src/optional/context.ts
@@ -8,7 +8,7 @@ interface ProviderProps {
   value: any
 }
 
-export class Provide extends Component<{}, ProviderProps> {
+export class Provide extends Component<ProviderProps> {
   updateValue() {
     // TS doesn't allow symbol as index :/
     // https://github.com/Microsoft/TypeScript/issues/24587
diff --git a/packages/core/src/optional/keepAlive.ts b/packages/core/src/optional/keepAlive.ts
index 00d1aa18..1525b37d 100644
--- a/packages/core/src/optional/keepAlive.ts
+++ b/packages/core/src/optional/keepAlive.ts
@@ -15,7 +15,7 @@ type Cache = Map<CacheKey, VNode>
 
 export const KeepAliveSymbol = Symbol()
 
-export class KeepAlive extends Component<{}, KeepAliveProps> {
+export class KeepAlive extends Component<KeepAliveProps> {
   cache: Cache = new Map()
   keys: Set<CacheKey> = new Set()
 
diff --git a/packages/core/src/vdom.ts b/packages/core/src/vdom.ts
index 9f3185c0..14b85f74 100644
--- a/packages/core/src/vdom.ts
+++ b/packages/core/src/vdom.ts
@@ -27,8 +27,9 @@ export interface VNode {
   slots: Slots | null
   // only on mounted nodes
   el: RenderNode | null
-  // only on mounted component root nodes
-  // points to component node in parent tree
+  // only on mounted component nodes that is also a root node (HOCs)
+  // points to parent component's placeholder vnode
+  // this is used to update vnode.el for nested HOCs.
   parentVNode: VNode | null
 }
 
@@ -56,12 +57,12 @@ export type Key = string | number
 
 export type Ref = (t: RenderNode | MountedComponent | null) => void
 
-export interface Slots {
-  [name: string]: Slot
-}
-
 export type Slot = (...args: any[]) => VNode[]
 
+export type Slots = Readonly<{
+  [name: string]: Slot
+}>
+
 export function createVNode(
   flags: VNodeFlags,
   tag: string | FunctionalComponent | ComponentClass | RenderNode | null,
diff --git a/packages/renderer-dom/src/components/transition-group.ts b/packages/renderer-dom/src/components/transition-group.ts
new file mode 100644
index 00000000..e69de29b
diff --git a/packages/renderer-dom/src/components/transition.ts b/packages/renderer-dom/src/components/transition.ts
new file mode 100644
index 00000000..e69de29b
diff --git a/packages/vue/__tests__/compat.spec.ts b/packages/vue/__tests__/compat.spec.ts
index b1aa63c2..580e202d 100644
--- a/packages/vue/__tests__/compat.spec.ts
+++ b/packages/vue/__tests__/compat.spec.ts
@@ -7,7 +7,7 @@ describe('2.x compat build', async () => {
     const root = document.createElement('div')
     document.body.appendChild(root)
 
-    const instance = new Vue({
+    const instance = new Vue<any>({
       data() {
         return { count: 0 }
       },
diff --git a/packages/vue/src/index.ts b/packages/vue/src/index.ts
index a7dea494..53b9e2da 100644
--- a/packages/vue/src/index.ts
+++ b/packages/vue/src/index.ts
@@ -6,13 +6,19 @@ import {
   ComponentOptions,
   createComponentInstance
 } from '@vue/renderer-dom'
+import { MergedComponent } from '../../core/src/component'
 
-class Vue extends Component {
+class Vue<
+  P extends object = {},
+  D extends object = {},
+  M extends object = {},
+  C extends object = {}
+> extends Component {
   static h = h
   static render = render
   static nextTick = nextTick
 
-  constructor(options: ComponentOptions & { el?: any }) {
+  constructor(options: ComponentOptions<P, D, M, C> & { el?: any }) {
     super()
     if (!options) {
       return
@@ -43,5 +49,9 @@ class Vue extends Component {
   }
 }
 
+interface Vue<P, D, M, C> {
+  $mount(el: any): MergedComponent<P, D> & M & C
+}
+
 export default Vue
 export * from '@vue/renderer-dom'