5.0.2 T extends GenericType<infer InferredType> no longer resolves as true

[markglattback]

Bug Report

In previous versions of TypeScript (including 5.0.0-beta), when working with Vue, component prop types could be inferred using the following ExtractProps type where T is a Vue component:

import type { ComponentOptions } from 'vue'

type ExtractProps<T> = T extends ComponentOptions<infer Props> ? Props : never

The returned type is now never.

🔎 Search Terms

infer, generic

🕗 Version & Regression Information

5.0.0-rc

• This changed between versions 5.0.0-beta and 5.0.0-rc

💻 Code

import type { ComponentOptions } from 'vue'
import MyComponent from './MyComponent.vue'

type ExtractProps<T> = T extends ComponentOptions<infer Props> ? Props : never

type MyComponentProps = ExtractProps<typeof MyComponent> // never (but correctly returned Props in earlier versions of TS)

⏯ Playground Link

Working (4.9.5)

Broken (5.0.2)

🙁 Actual behavior

MyComponentProps is never

🙂 Expected behavior

MyComponentProps should be the inferred Props type

[RyanCavanaugh]

We'd need a self-contained repro (i.e. 3-50 lines, none of which import the entirety of Vue) in order to determine if this is an intentional change or not.

[kasperpeulen]

@markglattback Why did you close this? I'm investigating this as well, this broke TS support for Vue in storybook.

[markglattback]

@kasperpeulen whilst the old approach was no longer working with TS 5.0.x, the following has helped:

I stumbled across a comment from the author of Volar recommending vue-component-type-helpers to extract component types. I found that in our project it was dependent on having a d.ts file containing component types but otherwise works very well. In our case our d.ts file is generated by the unplugin-vue-components plugin.

We're also using Storybook 7 and have no issues with type inference using Meta<typeof MyComponent> or Story<typeof MyComponent>.

[kasperpeulen]

@markglattback Thanks for that! That is really useful.

I opened a PR in storybook to use those type helpers:
storybookjs/storybook#22814

Weird that you don't have issues in storybook, we have multiple users report that it breaks with TS 5.0.