main.js

// @flow

import EventEmitter from 'eventemitter3';
class foo extends EventEmitter {

}

const x = new foo();
x.bar(); //Should error as bar is not a method of foo. - does not. Changing

output

> flow version
Flow, a static type checker for JavaScript, version 0.22.0
> flow check
main.js:9
  9: x.bar(); //Should error as bar is not a method of foo. - does not. Changing
       ^^^ property `bar`. Property not found in
  9: x.bar(); //Should error as bar is not a method of foo. - does not. Changing
     ^ foo


Found 1 error

test.js

declare module 'eventemitter3' {
      declare class EventEmitter {}
          declare var exports: Class<EventEmitter>;
}