Type error when using generic with withDefaults about core

[jh-leong]

@thomasaull try this

[thomasaull]

Thanks @jh-leong! The only thing necessary to make it work, seems to be to update the type on Props to include the default type I want to use, so this works:

interface Props {
  type?: TypeBase | Type
}

as well as this

interface Props {
  type?: 'text' | Type
}

Example

[jh-leong]

This behavior is expected: TS Playground

const foo = <T extends 'foo'>() => {
  const a: { k: T } = { k: 'foo' } // error!
  // Type '"foo"' is not assignable to type 'T'.
  // '"foo"' is assignable to the constraint of type 'T', but 'T' could be instantiated with a different subtype of constraint '"foo"'.ts(2322)
}

For example, never is also a subtype of 'foo'.

[thomasaull]

Is there any other workaround than // @ts-expect-error or using runtime code to provide defaults (e.g. via computed)

[jh-leong]

@thomasaull Based on your previous example, would this approach work for your needs without using generics?

interface Props {
  type?: 'text' | 'date' | null
}

const props = withDefaults(defineProps<Props>(), {
  type: 'text'
})

[thomasaull]

@jh-leong Yeah no, I want to use the generic to set a type for a component which wraps an <input/> element, here's an example