TS problems with WritableComputedRef and generic types

[leopiccionia]

Version

3.0.0-alpha.2

Reproduction link

https://www.typescriptlang.org/play/index.html#code/JYWwDg9gTgLgBAbzgYwuArjApgEwDRxRYBmcAvnMVGnAOQACAbulgPRECGyMwjwMAT1oAoYcXQA7bsAgSUnbACUSACmAT wDgBsAajpYAuOBPQgARligBKRMLgOUsgM7wAHnAC8hVes079bRZre0dUCVc4AS8nDGwcFQRQx0cAcywYYxVbTwA ODcAOkYDLDxklLhnDKySoKxjUwsrHPykyo6C4tKYupYKlLIKshCUohh0KDkkNwJooaGxSWlZeSwOJRIAJgAeABVctQ0eANLjPdt2sJd3GKJiI-89UtHriPho71Q43ESBtJqcGyXnyRT6ZX DmqmSB4POrTsnUqYJ63nBkPIw1eDnGk2mBTmmMWwmQCiwygeABYtiFSetNsRdk1LFBDtTrEA

Steps to reproduce

import { computed, ref } from '@vue/reactivity'

function createRef(initialValue: number) {
    const x = ref(initialValue)
    const y = computed({
        get: () => x.value,
        set: (value: number) => {
            x.value = value
        }
    })
    return { x, y }
}

function createRef2<T>(initialValue: T) {
    const x = ref(initialValue)
    const y = computed({
        get: () => x.value,
        set: (value: T) => {
            x.value = value
        }
    })
    return { x, y }
}

createRef(42)
createRef2(42)

What is expected?

I expect createRef2 to work without issues, just like createRef, with y inside createRef2 having type WritableComputedRef<T>.

What is actually happening?

TypeScript can't deduce type of y inside createRef2.

---

It may be just a misunderstanding of new Vue API, but seemed like a bug to me at first.

[yyyanghj]

Just remove the setter's type and it works well

[himself65]

I think this issue has fixed in the latest version.

[leopiccionia]

@himself65 Indeed, it's fixed if I upgrade to 3.0.0-alpha.7 and use shallowRef instead of ref.