Version

3.1.1

Reproduction link

https://sfc.vuejs.org/#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

Steps to reproduce

as the code in the SFC Playground,when i set deep:true,the oldValue is same as val.but when i use ()=>[...array],I get the correct oldValue

What is expected?

get the right oldValue when deep is true

What is actually happening?

wrong oldValue

https://v3.vuejs.org/guide/reactivity-computed-watchers.html#watching-reactive-objects

https://v3.vuejs.org/guide/reactivity-computed-watchers.html#watching-reactive-objects

thanks