This change ensures that when hoisting an identifier we do not hoist it up to
the first no shadowed function, but rather up to the bound shadowed function
* Flip default parameter template
YMMV, I saved ~10b on a 2kb library. Not noticeable at the small scale, by why not do it anyway?
I've (unscientifically) found that flipping the default parameter conditional yields better gzip results. I think this is due to the slightly longer string it can now repeatedly match:
```js
// old
var param = arguments.length <= 0 || void 0 === arguments[0] ? null : arguments[0]
--------------------------------------------------------------^
// new
var param = arguments.length > 1 && void 0 !== arguments[1] ? arguments[1] : null
------------------------------------------------------------------------^
```
Though it's entirely likely gzip will also choose up to the index of the arguments if you many default parameters at different indexes.
* Update tests
* Removed unnecessary 'return' statements.
Returning a 'Promise' value in 'promise.then()' makes promise chains.
Used memory and promises are not garbage collected
until finishing 'helpers.asyncToGenerator'.
* Update test
* Fix class inheritance in IE9 & IE10 (T3041)
Internet Explorer 9&10 do not support __proto__ at all, don't have
Object.setPrototypeOf(), but have Object.getPrototypeOf().
Because of this setting the prototype is not possible, which makes the
babelHelpers.inherits() function to set __proto__ although not supported.
Afterwards Object.getPrototypeOf() is used, but this one is not
respecting the "custom" property __proto__ that we set.
The solution is to check for __proto__ first and afterwards fallback to
Object.getPrototypeOf().
* Do the same logic in babel-helper-replace-supers
* Fix tests
* Extract creation of prototype nodes to small helper
I previously tried an approach to scope bindings from var to scope but
it didn't catch all cases. This is evident in this bug:
https://phabricator.babeljs.io/T2892
Where even after transforming a const to a var we still get an error
that it's read-only.
This approach will go through and delete every existing let and const
binding and creates a new one with the kind "var"
Rather than repeating the original location when we exit a node, we need to restore the previous parent’s original line location, since the source map format denotes the start location.
