Flow: "unexpected typeapp: EmptyT" error after upgrading to flow 0.70.0

Created on 23 Apr 2018 · 4Comments · Source: facebook/flow

After upgrading from flow 0.69.0 to 0.70.0 I am now seeing the following flow errors:

Error ┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈ node_modules/ux/src/FileUpload/FileUpload.js.flow:67:17

Internal error: unexpected typeapp: EmptyT

     64│    static defaultProps = {
     65│        defaultText: 'Click here or drag and drop a file to begin upload',
     66│        isOver: false,
     67│        onUpload: (): Promise<any> => Promise.resolve(),
     68│        releaseText: 'Release to begin upload...',
     69│        uploadingText: 'Uploading...',
     70│    };


Error ┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈ node_modules/ux/src/FileUpload/FileUpload.js.flow:213:49

Internal error: unexpected typeapp: EmptyT

     210│    * Handler for the file drop event on the file uploader
     211│    */
     212│   // eslint-disable-next-line react/no-unused-prop-types
     213│   _handleDrop = ({files}: {files: Array<File>}): Promise<any> => {
     214│       // Validate files
     215│       const validationError = this._validate(files);
     216│       if (validationError) {


Error ┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈ node_modules/ux/src/FileUpload/FileUpload.js.flow:240:55

Internal error: unexpected typeapp: EmptyT

     237│   /*
     238│    * Handle for the file upload select event
     239│    */
     240│   _handleInputSelect = (event: SyntheticInputEvent<>): Promise<any> => {
     241│       event.preventDefault();
     242│
     243│       // Find file objects

The errors all seem to be pointing at the Promise<*> definitions inside a third-party node_module library I'm using.

I've tried modifying the Promise type definitions to be more specific but that doesn't seem to make any difference. Changing the Promise type definitions to any in the third-party library code makes the issues go away. So it seems to be something to do with the default Promise type definition inside Flow itself.

Rolling back to flow 0.69.0 makes the issues go away.

Could anyone suggest any ideas about what unexpected typeapp: EmptyT might be referring to and what it may have to do with the Promise type definitions?

bug

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