Flow does not infer type on spread

[pronebird]

Flow is a little dumb when it comes to spread.

// @flow

const data = {
  event: ((): string => { return 'archive' })(),
  createdAt: +Date.now(),
  id: 1,
};

(data: {
 event: string,
 createdAt: number,
 id: number,
});

({
  ...data,
  event: 'archive',
  createdAt: new Date(data.createdAt),
}: {
  event: 'archive',
  createdAt: Date,
 id: number,
})

Gives the following output:

15: ({
     ^ Cannot cast object literal to object type because number [1] is incompatible with `Date` [2] in property `createdAt`.
References:
11:  createdAt: number,
                ^ [1]
21:   createdAt: Date,
                 ^ [2]
15: ({
     ^ Cannot cast object literal to object type because string [1] is incompatible with string literal `archive` [2] in property `event`.
References:
10:  event: string,
            ^ [1]
20:   event: 'archive',
             ^ [2]

Wat? 🤔

[wchargin]

Duplicate of #6108.