Type properties in discriminated union types

Question

I want to create a discriminated union where all objects are of another type.

say i have a type

type PersonNames = 'john' | 'kate'
type Person = {
  name: PersonNames,
  favorites: unknown // can be any object
}

and i want to create a PersonPreferences type that is a union of Person objects such that only PersonNames is allowed for name...

type PersonPreferences = 
| {
   name: 'john'.
   favorites: {
     food: 'pizza'
   }
| {
   name: 'kate',
   favorites: {
     book: 'horror'
   }

How can this be accomplished?

I tried this but it allows for arbitrary names

type PersonPreferences = Person & (
| {
   name: 'john'.
   favorites: {
     food: 'pizza'
   }
| {
   name: 'jimmy',  // should error
   favorites: {
     book: 'science'
   }
)