chore: dts-test vuejs#12978

Author: simlevesque

types/test/v3/reactivity-test.ts

@@ -15,7 +15,7 @@ import {
   set,
   del
 } from '../../index'
-import { describe, expectType } from '../utils'
+import { IsUnion, describe, expectType } from '../utils'
 
 function plainType(arg: number | Ref<number>) {
   // ref coercing
@@ -385,3 +385,14 @@ describe('set/del', () => {
   // @ts-expect-error
   del([], 'fse', 123)
 })
+
+
+{
+  //#12978
+  type Steps = { step: '1' } | { step: '2' }
+  const shallowUnionGenParam = shallowRef<Steps>({ step: '1' })
+  const shallowUnionAsCast = shallowRef({ step: '1' } as Steps)
+
+  expectType<IsUnion<typeof shallowUnionGenParam>>(false)
+  expectType<IsUnion<typeof shallowUnionAsCast>>(false)
+}

types/test/v3/watch-test.ts

@@ -1,4 +1,4 @@
-import { ref, computed, watch } from '../../index'
+import { ref, computed, watch, shallowRef } from '../../index'
 import { expectType } from '../utils'
 
 const source = ref('foo')
@@ -76,3 +76,17 @@ watch([someRef, otherRef], values => {
   // no type error
   console.log(value2.a)
 })
+
+{
+  //#12978
+  type Steps = { step: '1' } | { step: '2' }
+  const shallowUnionGenParam = shallowRef<Steps>({ step: '1' })
+  const shallowUnionAsCast = shallowRef({ step: '1' } as Steps)
+
+  watch(shallowUnionGenParam, value => {
+    expectType<Steps>(value)
+  })
+  watch(shallowUnionAsCast, value => {
+    expectType<Steps>(value)
+  })
+}