Flow: View can be a string?

Is this a bug report?

Yes

Have you read the Contributing Guidelines?

Yes

Environment

1. react-native -v:

react-native-cli: 2.0.1
react-native: 0.48.2

1. node -v:

v8.4.0

1. npm -v:

5.4.1

1. flow version:

Flow, a static type checker for JavaScript, version 0.51.1

Then, specify:

• Target Platform: N/A, Flow static typesystem

• Development Operating System: macOS

• Build tools: N/A, Flow static typesystem

Steps to Reproduce

render() {
  return <View ref={(view: ?View) => {}} />;
}

1. Flow errors out because it thinks View is a string.

Expected Behavior

View should be a React.Component.

Actual Behavior

1. View is the result of calling requireNativeComponent()
2. requireNativeComponent returns React$ComponentType<any> | string
3. Consequently, Flow thinks View can be a string

Reproducible Demo

// @flow

import React from 'react';
import { View } from 'react-native';

class Test extends React.PureComponent {

  render() {
    return <View ref={(view: ?View) => {}} />;
  }

}

[bvaughn]

FYI this issue should be fixed by 11b4084. Someone (who has permissions to do so) can probably close this issue.

[bvaughn]

Unfortunately I can’t assign this issue to myself for some reason, but I’ll create a PR shortly that will hopefully provide a meaningful default Flow type for host components. Will post back here once it’s done.