Computed property ['__proto__'] not being assigned with defineProperty (T7223) #4188

Issue originally made by Andrew Bradley (cspotcode)

Bug information

• Babel version: 6.6.5
• Node version: 4.2.1
• npm version: 2.14.7

Options

{
    "presets": ["es2015"]
}

Input code

require('assert');
var obj = {
  ['__proto__']: {'assigned with': 'assignment operator', bar: 'baz'},
  ['foo']: {'assigned with': 'defineProperty'}
};
assert(obj.bar === undefined);

Description

When an object literal sets a computed property "proto", it shouldn't modify the object's prototype. However, Babel is emitting code that does modify the prototype because it's not using defineProperty. This behavior seems to be unique to __proto__ since other computed properties properly use defineProperty.

https://babeljs.io/repl/#?evaluate=true&presets=es2015%2Cstage-2&experimental=false&loose=true&spec=false&playground=false&code=var%20a%20%3D%20%7B%0A%20%20%5B%22__proto__%22%5D%3A%20%7B%22assigned%20with%22%3A%20%22assignment%20operator%22%2C%20bar%3A%20'baz'%7D%2C%0A%20%20%5B%22foo%22%5D%3A%20%7B%22assigned%20with%22%3A%20%22defineProperty%22%7D%0A%7D%3B%0A%2F%2F%20should%20be%20undefined%2C%20but%20it's%20%22baz%22%0Aalert(a.bar)%3B&stage=0