types(runtime-core): add OnCleanup parameter type in this.$watch

packages/dts-test/watch.test-d.ts

@@ -5,10 +5,13 @@ const source = ref('foo')
 const source2 = computed(() => source.value)
 const source3 = () => 1
 
+type OnCleanup = (fn: () => void) => void
+
 // lazy watcher will have consistent types for oldValue.
-watch(source, (value, oldValue) => {
+watch(source, (value, oldValue, onCleanup) => {
   expectType<string>(value)
   expectType<string>(oldValue)
+  expectType<OnCleanup>(onCleanup)
 })
 
 watch([source, source2, source3], (values, oldValues) => {
@@ -85,9 +88,10 @@ defineComponent({
   created() {
     this.$watch(
       () => this.a,
-      (v, ov) => {
+      (v, ov, onCleanup) => {
         expectType<number>(v)
         expectType<number>(ov)
+        expectType<OnCleanup>(onCleanup)
       }
     )
   }

packages/runtime-core/src/apiWatch.ts

@@ -66,7 +66,7 @@ type MapSources<T, Immediate> = {
       : never
 }
 
-type OnCleanup = (cleanupFn: () => void) => void
+export type OnCleanup = (cleanupFn: () => void) => void
 
 export interface WatchOptionsBase extends DebuggerOptions {
   flush?: 'pre' | 'post' | 'sync'

packages/runtime-core/src/componentPublicInstance.ts

@@ -5,7 +5,12 @@ import {
   isStatefulComponent
 } from './component'
 import { nextTick, queueJob } from './scheduler'
-import { instanceWatch, WatchOptions, WatchStopHandle } from './apiWatch'
+import {
+  instanceWatch,
+  OnCleanup,
+  WatchOptions,
+  WatchStopHandle
+} from './apiWatch'
 import {
   EMPTY_OBJ,
   hasOwn,
@@ -222,8 +227,8 @@ export type ComponentPublicInstance<
   $watch<T extends string | ((...args: any) => any)>(
     source: T,
     cb: T extends (...args: any) => infer R
-      ? (...args: [R, R]) => any
-      : (...args: any) => any,
+      ? (...args: [R, R, OnCleanup]) => any
+      : (...args: [any, any, OnCleanup]) => any,
     options?: WatchOptions
   ): WatchStopHandle
 } & IfAny<P, P, Omit<P, keyof ShallowUnwrapRef<B>>> &