Does not apply propTypes using `$Exact<>`

I am using $Exact<> to ensure that only certain props are passed to a component (flow will fail if any others are passed). I understand that checking for extraneous props is not easily handled with propTypes, but all type definitions wrapped in $Exact<> are ignored.

This works:

type ComponentProps = {
    someProp: string,
};

This does write any propType checks:

type ComponentProps = $Exact<{
    someProp: string,
}>;

[gcanti]

https://github.com/brigand/babel-plugin-flow-react-proptypes/pull/51

[gabro]

See also https://github.com/facebook/flow/pull/2525 for the WIP documentation 😉