jeffmo

let foo: ?number;

function bar() {
  if (foo == null) {
    return;
  }
  
  setTimeout(() => {
    // I refined above, so this should work right?
    // (hint: wrong. If `foo` were const, then it would be a correct/more intuitive assumption)

jeffmo

var a: mixed = foo();
var b: number;

b = a; // error! `a` might not be a number... Could be anything!

if (typeof a === 'number')) {
  b = a; // This is safe -- no error
} else {
  throw new Error('Unexpected type of `a`!');
}

jeffmo

// @flow

const a: number = 'asdf';
const b: string = 2;

jeffmo

###master (next release)

###v0.23.1

• Fixed parsing of JSON files with duplicate object keys

###v0.23.0

Likely to cause new Flow errors:

• When you refine a mixed variable with typeof myVar === 'object', we used to refine the type of myVar to null | Object. Now it is refined to null | {[key: string]: mixed}. This means myVar.prop has the type mixed rather than any.

jeffmo

// @flow
var a = 42;
export default a;

jeffmo

// @flow


declare function getElem(name: 'a'): HTMLCollection<HTMLAnchorElement>;
declare function getElem(name: 'button'): HTMLCollection<HTMLButtonElement>;

function getElem(name) {
  if (name === 'a') {
    return new HTMLCollection(/*...*/);
  } else {

jeffmo

// @flow


declare function getElem(name: 'a'): HTMLCollection<HTMLAnchorElement>;
declare function getElem(name: 'button'): HTMLCollection<HTMLButtonElement>;

function getElem(name) { return (42: any); };

let a: HTMLCollection<HTMLButtonElement> = getElem('a'); // Error
let b: HTMLCollection<HTMLAnchorElement> = getElem('a'); // No Error

jeffmo

// @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

jeffmo

{"passed":true,"errors":[],"version":"1d57ebd3661650edcecc6a3924d3353c70407966 Feb  1 2016 18:11:05"}

jeffmo

function foo({bar: {baz}}: SomeType) {}