Jeff Morrison jeffmo

###master (next release)

###v0.23.1

###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.

	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)

	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`!');
	}

	// @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 {

	// @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

	// @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