Flow: Spreading $Shape of exact type is same as spreading of same exact type

[PeteJodo]

It seems when spreading a $Shape of an exact type, it doesn't actually spread on type $Shape<T> but just spreads on T instead. The following breaks in try flow

type A = {| foo: number |};
type B = {| bar: string |};
type C<T, U> = {|
   ...T,
   ...$Shape<U>
|};

const c: C<A, B> = { // Error, property `bar` missing
  foo: 1
};

[orlandoc01]

Any updates on this issue? Is this a bug then in flow or are we misusing the spread operator with the $Shape type because we don' understand some behavior going on here?

[kvchen]

Shape doesn't behave quite as it states in the docs. To make all the keys optional, you can do something like this:

type Partial<T> = $Exact<{...{...T}}>;

Here's a link to Try Flow: https://flow.org/try/#0C4TwDgpgBACghgJ2ASzgGwDwBUB8UC8UAJAKIAecAxsBgN4B0jDjWAvqzgNwBQ3okUAIIEotAD5QAZgHtpALigA7AK4BbAEYQEUMax79oAIRHio6xAoDOwBMkUBzHXr7hoAYWwAaKAFU8hcW4oYMZ6LE8gkMZ4JFRMP25dHm5KaUVrKEoFD0FvQ39RSJl5KABGCODzAC8FABZuPSA

[orlandoc01]

Ok, I've been using the following instead actually:

type Partial<T> = $Rest<T, {}>;

https://flow.org/try/#0C4TwDgpgBACghgJ2ASzgGwDwBUB8UC8UAJAEoQDOw2ANFAN4C+OA3AFCuiRQCCB9APlABmAexEAuKADsArgFsARhARR+DNp2gAhPnUELEkygmRSA5qvUdw0AMI0oAVTyE9rKB4B03rNXdfveCRUTGdWNTZWAGMRKUooKMl7blotF3p-UQkoAEY-dSA

[kevinbarabash]

Would it make sense to define $Shape's as $Rest<T, {}>? Are there things that rely on $Shape's behavior that wouldn't work this change?