Shape objects

[Cyril Auburtin]

I wish JS had Shape objects, which would not only ease performance
optimization for the benefit of JS engines (
https://youtu.be/5nmpokoRaZI?t=871), but also helps for validation, like an
interface

```js
shape Point { x: Number, y: Number, name: String };

const p = Point({x: 1, y: 2, name: 'foo'})

const p = Point({x: 1, y: 2, naem: 'foo'}) // throws
```

That object would have its properties immutable

I think proposal-first-class-protocols (
https://github.com/michaelficarra/proposal-first-class-protocols/issues/27#issuecomment-386975099)
could more or less directly do that feature
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.mozilla.org/pipermail/es-discuss/attachments/20180616/bbf862ff/attachment.html>