Sub-Component type check: optional fields are mis interpolated when kebab-cased

[AlexandreBonaventure]

• I have searched through existing issues
• I have read through docs
• I have read FAQ

Info

• Platform: macOS
• Vetur version: 0.28.0
• VS Code version: 1.49.1

Problem

For a given component defined like such :

defineComponent({
  props: {
    iconPosition: {
      type: String as () => 'left'|'right',
      default: 'left',
      required: false,
    },
  },
})

What's happening ?

for icon-position typings are interpreted as 'icon-position?' : any

What's expected ?

for icon-position typings should put the question mark outside the string key like that: 'icon-position'? : any

Reproducible Case

Coming soon I promise

[yoyo930021]

Duplicate of #2314