opened
dannysmc95
username_0
### Version
3.0.0-rc.11

### Reproduction link
[https://github.com/username_0/vue3-issue1](https://github.com/username_0/vue3-issue1)

### Steps to reproduce
!! Please note I have added `vue-next` as Vue3 is NOT available on the bug reporter, this was created using @vue/cli using the Vue 3 Preview feature.

1. Pull the repo link, and do npm install,
2. Run npm run serve,
3. View the page in the browser, with the vue-devtools installed and the console open (I use Chrome),
4. Uncomment the public random line,
5. See the error in the console,

### What is expected?
There should be no error and the p tag should still display the text.

Unless I am doing something wrong, but I don't believe so, I have removed the access definitions (public, private, etc), and no change.

### What is actually happening?
I am seeing an error relating to reactivity, and it breaks the page, stopping the p tag from showing and forcing me to refresh the page each time, which kind of defeats the point of HMR.

See error output:

runtime-core.esm-bundler.js?5c40:38 [Vue warn]: Property "message" was accessed during render but is not defined on instance.  
  at <Anonymous onVnodeUnmounted=fn<onVnodeUnmounted> ref=Ref< null > >  
  at <RouterView>  
  at <App>  
warn	@	runtime-core.esm-bundler.js?5c40:38  
get	@	runtime-core.esm-bundler.js?5c40:5696  
render	@	Home.vue?bb51:3  
renderComponentRoot	@	runtime-core.esm-bundler.js?5c40:535  
componentEffect	@	runtime-core.esm-bundler.js?5c40:4286  
reactiveEffect	@	reactivity.esm-bundler.js?a1e9:42  
effect	@	reactivity.esm-bundler.js?a1e9:17  
setupRenderEffect	@	runtime-core.esm-bundler.js?5c40:4269  
mountComponent	@	runtime-core.esm-bundler.js?5c40:4227  
processComponent	@	runtime-core.esm-bundler.js?5c40:4183  
patch	@	runtime-core.esm-bundler.js?5c40:3788  
componentEffect	@	runtime-core.esm-bundler.js?5c40:4373  
reactiveEffect	@	reactivity.esm-bundler.js?a1e9:42  
callWithErrorHandling	@	runtime-core.esm-bundler.js?5c40:154  
flushJobs	@	runtime-core.esm-bundler.js?5c40:359  
Promise.then (async)  
queueFlush	@	runtime-core.esm-bundler.js?5c40:259  
queueCb	@	runtime-core.esm-bundler.js?5c40:281  
queuePostFlushCb	@	runtime-core.esm-bundler.js?5c40:287  
eval	@	runtime-core.esm-bundler.js?5c40:473  
reload	@	runtime-core.esm-bundler.js?5c40:459  
eval	@	runtime-core.esm-bundler.js?5c40:499  
eval	@	VM1034 Home.vue:14  
./src/views/Home.vue	@	app.js:1057  
__webpack_require__	@	app.js:849  
hotApplyInternal	@	app.js:750  
hotApply	@	app.js:412  
(anonymous)	@	app.js:387  
Promise.then (async)  
hotUpdateDownloaded	@	app.js:386  
hotAddUpdateChunk	@	app.js:362  
webpackHotUpdateCallback	@	app.js:58  
(anonymous)	@	app.28fcc07….hot-update.js:1  

---
!! Please note I have added `vue-next` as Vue3 is NOT available on the bug reporter.

<!-- generated by vue-issues. DO NOT REMOVE -->
Property "message" was accessed during render but is not defined on instance. - Vue 3 & TypeScript
issue