title: Named default ES6 parameter without destructuration
body: <p>I'm trying to default options in ES7 using babel. Here is what I can do:</p>
  
  <pre><code>class Foo {
    constructor({key='value', foo='bar', answer=42}) {
      this.key = key; 
      this.foo = foo;
      this.number = number;
    }
  }
  </code></pre>
  
  <p>This might work for this example, but I would like to know how can I assign for very large config objects; <strong>here is an example of what I wanna do:</strong></p>
  
  <pre><code>class Foo {
    constructor(opts = {key='value', foo='bar', answer=42}) {
      this.opts = opts;
    }
  }
  </code></pre>
  
  <p>However this does not compile. I tried to do it like this:</p>
  
  <pre><code>class Foo {
    constructor(opts = {key:'value', foo:'bar', answer:42}) {
      this.opts = opts;
    }
  }
  </code></pre>
  
  <p>But then it replaces the whole object, like this:</p>
  
  <pre><code>let foo = new Foo({key: 'foobar'});
  
  console.log(foo.opts);
  // {key: 'foobar'} is what is displayed
  // When I want {key: 'foobar', foo:'bar', answer:42}
  </code></pre>