// bar.js

export function bar(a) {

    return a;

}

 

// foo.js

import { bar } from './bar';

export function foo(a) {

    return bar(a);

}

 

// index.js

import { foo } from './foo';

const f: number = foo(1);

flowcheck

// bar.js

export function bar(a) {

    return a;

}

 

// foo.js

import { bar } from './bar';

export function foo(a) {

    return bar(a);

}

 

// index.js

import { foo } from './foo';

const f: number = foo(1);

flowcheck

exports = {

    bar: (T) => T

}

// bar.js

export function bar(a) {

    return a;

}

 

// foo.js

import { bar } from './bar';

export function foo(a) {

    return bar(a);

}

 

// index.js

import { foo } from './foo';

const f: number = foo(1);

flowcheck

flowcheck

exports = {

    bar: (?) => ?

}

// bar.js

export function bar(a) {

    return a;

}

 

// foo.js

import { bar } from './bar';

export function foo(a) {

    return bar(a);

}

 

// index.js

import { foo } from './foo';

const f: number = foo(1);

flowcheck

flowcheck

exports = {

    bar: (?) => ?

}

exports = {

    foo: (?) => ?

}

// bar.js

export function bar(a) {

    return a;

}

 

// foo.js

import { bar } from './bar';

export function foo(a) {

    return bar(a);

}

 

// index.js

import { foo } from './foo';

const f: number = foo(1);

flowcheck

flowcheck

flowcheck

exports = {

    bar: (?) => ?

}

exports = {

    foo: (?) => ?

}

// bar.js

export function bar(a) {

    return a;

}

 

// foo.js

import { bar } from './bar';

export function foo(a) {

    return bar(a);

}

 

// index.js

import { foo } from './foo';

const f: number = foo(1);

foo(number)

flowcheck

flowcheck

flowcheck

exports = {

    bar: (?) => ?

}

exports = {

    foo: (number) => ?

}

// bar.js

export function bar(a) {

    return a;

}

 

// foo.js

import { bar } from './bar';

export function foo(a) {

    return bar(a);

}

 

// index.js

import { foo } from './foo';

const f: number = foo(1);

foo(number)

flowcheck

flowcheck

flowcheck

exports = {

    bar: (number) => number

}

exports = {

    foo: (number) => ?

}

// bar.js

export function bar(a) {

    return a;

}

 

// foo.js

import { bar } from './bar';

export function foo(a) {

    return bar(a);

}

 

// index.js

import { foo } from './foo';

const f: number = foo(1);

foo(number)

flowcheck

flowcheck

flowcheck

exports = {

    bar: (number) => number

}

exports = {

    foo: (number) => number

}

// bar.js

export function bar(a) {

    return a;

}

 

// foo.js

import { bar } from './bar';

export function foo(a) {

    return bar(a);

}

 

// index.js

import { foo } from './foo';

const f: number = foo(1);

foo(number)

flowcheck

flowcheck

flowcheck

exports = {

    bar: (number) => number

}

exports = {

    foo: (number) => number

}

// bar.js

export function bar(a) {

    return a;

}

 

// foo.js

import { bar } from './bar';

export function foo(a) {

    return bar(a);

}

 

// index.js

import { foo } from './foo';

const f: number = foo(1);

foo(number): number

// baz.js

import { bar } from './bar';

const b: string = bar('shopee');

// baz.js

import { bar } from './bar';

const b: string = bar('shopee');

exports = {

    bar: (number| string) => number | string

}

exports = {

    foo: (number) => number

}

foo(number): number

// bar.js

export function bar(a) {

    return a * 20;

}

 

// foo.js

import { bar } from './bar';

export function foo(a) {

    return bar(a);

}

 

// index.js

import { foo } from './foo';

foo(1);

exports = {

    foo: (number) => ?

}

exports = {

    foo: (number) => ?

}

// bar.js

export function bar(a) {

    return a * 20;

}

 

// foo.js

import { bar } from './bar';

export function foo(a) {

    return bar(a);

}

 

// index.js

import { foo } from './foo';

foo(1);

// bar.js

export function bar(a) {

    return a * 20;

}

 

// foo.js

import { bar } from './bar';

export function foo(a) {

    return bar(a);

}

 

// index.js

import { foo } from './foo';

foo(1);

flowcheck

exports = {

    foo: (number) => ?

}

exports = {

    foo: (number) => ?

}

// bar.js

export function bar(a) {

    return a * 20;

}

 

// foo.js

import { bar } from './bar';

export function foo(a) {

    return bar(a);

}

 

// index.js

import { foo } from './foo';

foo(1);

flowcheck

exports = {

    foo: (number) => number

}

exports = {

    foo: (number) => number

}

flowcheck

// bar.js

export function bar(a) {

    return a * 20;

}

 

// foo.js

import { bar } from './bar';

export function foo(a) {

    return bar(a);

}

 

// index.js

import { foo } from './foo';

foo(1);

flowcheck

exports = {

    foo: (number) => number

}

exports = {

    foo: (number) => number

}

flowcheck

flowcheck

Cannot find "fast flow worker" gif here

// bar.js

export function bar(a) {

    return a * 20;

}

 

// foo.js

import { bar } from './bar';

export function foo(a) {

    return bar(a);

}

 

// index.js

import { foo } from './foo';

foo(1);

1. function arguments

export function f(x) {}

export function f(x) {}

1: export function f(x) {}
                     ^ Missing type annotation for `x`.

2. writeable fields

class C { p; }
export default new C;

1: class C { p; }
             ^ Missing type annotation for property `p`.

class C { p; }
export default new C;

3. implicit instantiation

3. implicit instantiation

function ref<T>(): { value: T|null } {
  return { value: null };
}
module.exports = ref();

4: module.exports = ref();
                    ^ Missing type annotation for `T`. `T` is a type parameter declared in function [1] and was implicitly instantiated at call of `ref` [2].
References:

1: function ref<T>(): { value: T|null } {
   ^ [1]
4: module.exports = ref();

function ref<T>(): { value: T|null } {
  return { value: null };
}
module.exports = ref();