somefile.js

type Linkable = {
  name: string,
  profileURL: string
};

function bigOldObject () {
  return {
    id: 1,
    name: 'foo',
    email: 'foo@bar.com',
    avatarURL: '/wat.jpg',
    profileURL: '/user/1'
  };
}

function makeLink () {
  // Here we're explicitly saying that we only depend
  // on the 'Linkable' properties, despite the function
  // returning a larger object. 
  const subject: Linkable = bigOldObject();
  console.log(subject.id); // a flow error
  return <a href={subject.profileURL}>{subject.name}</a>;
}