types: improve ref sugar $computed typing

test-dts/refSugar.test-d.ts

@@ -1,3 +1,4 @@
+import { WritableComputedRef } from '@vue/reactivity'
 import {
   expectType,
   $ref,
@@ -22,7 +23,19 @@ expectType<{ foo: Ref<number> }>($shallowRef({ foo: ref(1) }))
 // $computed
 expectType<number>($computed(() => 1))
 let b = $ref(1)
-expectType<number>($computed(() => b))
+expectType<number>(
+  $computed(() => b, {
+    onTrack() {}
+  })
+)
+
+// writable computed
+expectType<number>(
+  $computed({
+    get: () => 1,
+    set: () => {}
+  })
+)
 
 function useFoo() {
   return {
@@ -45,3 +58,10 @@ expectType<Ref<string>>($raw(y))
 const c = $computed(() => 1)
 const cRef = $raw(c)
 expectType<ComputedRef<number>>(cRef)
+
+const c2 = $computed({
+  get: () => 1,
+  set: () => {}
+})
+const c2Ref = $raw(c2)
+expectType<WritableComputedRef<number>>(c2Ref)