Issue 1:
This is weird, right?

Module build failed: SyntaxError: /Users/quangbuule/Projects/React/mui-bug/src/index.js: 'super.*' is not allowed before super()
8 |
9 | constructor() {
> 10 | super(...arguments);

Issue 2:
Babel6 produces an error when trying to compile class without a constructor.

$ babel --version
6.0.15 (babel-core 6.0.20)
$ babel --presets react,es2015,stage-1 Hello.jsx
SyntaxError: Hello.jsx: 'super.*' is not allowed before super() (This is an error on an internal node. Probably an internal error)
undefined

Hello.jsx

var _ = require('underscore'),
React = require('react');

class Hello extends React.Component
{
state = {
hello: 1
};

/*
constructor() {
super();
}
*/

render() {
var props = _.omit(this.props, 'children');
return (
<p className="1" {... props}>Hello</p>
);
}

foo(param = 1) {
this.param = param;
}
}

module.exports = Hello;

After uncommenting the constructor it compiles:

$ babel --presets react,es2015,stage-1 Hello.jsx
'use strict';

var _extends = Object.assign || function (target) { for (var i = 1; i < arguments.length; i++) { var source = arguments[i]; for (var key in source) { if (Object.prototype.hasOwnProperty.call(source, key)) { target[key] = source[key]; } } } return target; };

var _createClass = (function () { function defineProperties(target, props) { for (var i = 0; i < props.length; i++) { var descriptor = props[i]; descriptor.enumerable = descriptor.enumerable || false; descriptor.configurable = true; if ("value" in descriptor) descriptor.writable = true; Object.defineProperty(target, descriptor.key, descriptor); } } return function (Constructor, protoProps, staticProps) { if (protoProps) defineProperties(Constructor.prototype, protoProps); if (staticProps) defineProperties(Constructor, staticProps); return Constructor; }; })();

function _classCallCheck(instance, Constructor) { if (!(instance instanceof Constructor)) { throw new TypeError("Cannot call a class as a function"); } }

function _possibleConstructorReturn(self, call) { if (!self) { throw new ReferenceError("this hasn't been initialised - super() hasn't been called"); } return call && (typeof call === "object" || typeof call === "function") ? call : self; }

function _inherits(subClass, superClass) { if (typeof superClass !== "function" && superClass !== null) { throw new TypeError("Super expression must either be null or a function, not " + typeof superClass); } subClass.prototype = Object.create(superClass && superClass.prototype, { constructor: { value: subClass, enumerable: false, writable: true, configurable: true } }); if (superClass) Object.setPrototypeOf ? Object.setPrototypeOf(subClass, superClass) : subClass.__proto__ = superClass; }

var _ = require('underscore'),
React = require('react');

var Hello = (function (_React$Component) {
_inherits(Hello, _React$Component);

function Hello() {
_classCallCheck(this, Hello);

var _this = _possibleConstructorReturn(this, Object.getPrototypeOf(Hello).call(this));

_this.state = {
hello: 1
};
return _this;
}

_createClass(Hello, [{
key: 'render',
value: function render() {
var props = _.omit(this.props, 'children');
return React.createElement(
'p',
_extends({ className: '1' }, props),
'Hello'
);
}
}, {
key: 'foo',
value: function foo() {
var param = arguments.length <= 0 || arguments[0] === undefined ? 1 : arguments[0];

this.param = param;
}
}]);

return Hello;
})(React.Component);

module.exports = Hello;