fix: avoid including Function type in inferred props type

[ktsn]

fix #291

The issue was caused by distribution of conditional types. The reason there is no issue when we declare props type via { type: String } format is T extends { type: PropType<infer V, boolean> } won't be distributed.

The solution is just avoiding distribution in the conditional types in InferPropType. To do that, I wrapped all conditional types with tuple.

[pikax]

this test is passing on master branch 🤔

[ktsn]

I guess this is because the behavior prior TS 3.9 because PropsType includes {} type which can be assigned to { user?: User }. 🤔

https://devblogs.microsoft.com/typescript/announcing-typescript-3-9-rc/

Generally, an intersection type like A & B is assignable to C if either A or B is assignable to C

Once I updated TS to 3.9, the test fails on master.

[pikax]

@antfu can we get this merged before release of 0.6.0?

Bug is still in master:

interface A {
  a: String
}

defineComponent({
  props: {
    a: Object as PropType<A>
  },
  setup(props){
    props.a
  }
})

[antfu]

This does not seems to fix for me:

Meanwhile, vue-next does not use this hack while solving the issue. I guess we need to rework the props typing to align with vue-next instead. And since the release has been delayed for too long, my plan would be delivering the release first and delay this PR into the next release so we can have more time to better take care of it.

[antfu]

Closing this in favor of #352. Thanks.