vue + compositionApi will cause memory leaks!

[ygj6]

Version

2.6.12

Reproduction link

https://codesandbox.io/s/billowing-butterfly-qe2yv?file=/src/App.vue

Steps to reproduce

See codesandbox for details, When the close button is clicked, the Vuecomponent memory will not be released compared to before the click.

I found that when the setup() {}, of the child component is commented out, the memory can be released normally.

What is expected?

Could release memory normally.

What is actually happening?

Memory leaks!

[ygj6]

@pikax @antfu
The detailed reproduction steps are:

1. Download the demo in the link and execute npm install and npm run serve;
2. Open the local URL ;
3. Open the developer tools, click the take heap snapshort button under the memory tab, and generate a memory snapshot A
4. Click the close button on the page to destroy the component, and repeat step 3 to generate a memory snapshot B;

Then we will find: B does not release memory compared to A

I think this is a memory leak bug, can you take a moment to look at this issue and PR?