How do LooseRequired<Props> work?

[DenFin]

I am currently facing an issue with defining default values for an optional prop. What kinda throws me of is that I am pretty sure this worked in the past.

I already searched for 'LooseRequired' in issues and discussions and on Stackoverflow but could not find anything that looked relevant.

Here is a minimal example:

<script setup lang="ts">
type SomeOptionalProp = {
  name: string;
};

type Props = {
  someOptionalProp?: SomeOptionalProp;
};

withDefaults(defineProps<Props>(), {
  someOptionalProp: {
    name: 'Test',
  },
});
</script>

This throws an 'Object literal may only specify known properties' error. You can check out the example in Stackblitz

At first I thought this might be because the default is an untyped object and if I would assert the type then the error would be resolved. When I assert the default like this

withDefaults(defineProps<Props>(), {
  someOptionalProp: {
    name: 'Test',
  } as SomeOptionalProp,
});

the error message changes to:

error TS2322: Type 'SomeOptionalProp' is not assignable to type '(props: LooseRequired<Props>) => SomeOptionalProp'.
  Type 'SomeOptionalProp' provides no match for the signature '(props: LooseRequired<Props>): SomeOptionalProp'.

Why is this happening? To me everything looks perfectly fine. Do I need to wrap SomeOptionalProp in some kind of helper type?

[DenFin]

I forgot to define the default as an arrow function:

withDefaults(defineProps<Props>(), {
  someOptionalProp: () => ({
    name: 'Test',
  }),
});