useCssModule is broken on Vue 2.7

[Ansett]

Version

2.7.11

Reproduction link

codesandbox.io

Steps to reproduce

const style = useCssModule()
console.log(style.someClass) // undefined
// ...
<style module lang="css">
.someClass {
  background: pink;
}
</style>

What is expected?

style object should contain defined class names

What is actually happening?

style object is empty.

In console: [Vue warn]: Current instance does not have CSS module named "$style"

---

I checked https://github.com/vuejs/core/blob/v2-compat/packages/runtime-dom/src/helpers/useCssModule.ts which uses getCurrentInstance, but on vue 2.7 getCurrentInstance returns { proxy: Vue }.
Maybe that's something else :p

[skirtles-code]

I believe this is the same issue as #12822.

[Ansett]

Seems so, I didn't search well enough :(

[haoqunjiang]

Let's close this and track it in #12822 instead.