type IsUnion<T> = [T] extends [UnionToIntersection<T>] ? false : true;

type MemberInfo = {
  first_name: string;
  last_name: string;
  date_of_birth: number;
  favourite_fruit: 'apple' | 'mango' | 'banana';
  industry: 'tech' | 'art' | 'medicine';
}

type ChoiceBasedField = {
  [K in keyof MemberInfo]: IsUnion<MemberInfo[K]> extends true ? K : never
}[keyof RespondentFields];

// can accept 'favourite_fruit' or 'industry', but errors on anything else
const renderDropdown = (field: ChoiceBasedField) => (
  <select> ... </select>
);