interface NuallablePerson {
    name?: string
}

interface Person extends NuallablePerson {
    name: string
}

const persons: NuallablePerson[] = [{}, {name: 'test'}, {}, {}]
const validPersons: Person[] = persons.filter(x => x.name)

// Type 'NuallablePerson[]' is not assignable to type 'Person[]'. Type 'NuallablePerson' is not assignable to type 'Person'. Types of property 'name' are incompatible. Type 'string | undefined' is not assignable to type 'string'. Type 'undefined' is not assignable to type 'string'.