### Version 2.7.10 ### Reproduction link [codesandbox.io](https://codesandbox.io/s/vue-2-playground-forked-h3qfie?file=/src/App.vue) ### Steps to reproduce ```js export default { name: "App", watch: { e: [ "handle1", function handle2(val, oldVal) {}, { handler: function handle3(val, oldVal) {}, }, ], }, }; ``` ### What is expected? no type error ### What is actually happening? type error <!-- generated by vue-issues. DO NOT REMOVE -->