* centralize plugin options
* Centralize plugins options
- move more options to the top
- move validations that depend on options to the top
* use isLoose option
* Move more validations to the top
* Move ref parameter for rewriteModuleStatementsAndPrepareHeader() to the top
* fix eslint errors
* remove unused parameter
* set default systemGlobal value
* Revert "Move ref parameter for rewriteModuleStatementsAndPrepareHeader() to the top"
This reverts commit b3855302d17fa19d8acb4c8accab3680c8d2710e.
* Revert "Move more validations to the top"
This reverts commit e5861d8a034ff8f553391f55654f753bcf428a5d.
* fix allowMutablePropsOnTags option usage
* improve naming
* change Contructor definition for sake of consistency
* move allowMutablePropsOnTags validation to the top
* add missing !
The arguments of a function would be unnecessarily copied if there was
a nested function that had a parameter with the same identifier as the
rest parameter for the outer function. This checks the scope of the
parameter is correct before deoptimising.
Fixes: https://github.com/babel/babel/issues/5656
Refs: https://github.com/babel/babel/issues/2091
* Handle arrow function processing via shared API rather than default plugin.
* Fix a few small PR comments.
* Preserve existing spec arrow 'this' rewrites, and support spec in subclass constructors.
When the rest parameter shared the same name as a default identifier
for a param, the loop would be hoisted outside the function!
```js
var a = 1;
for (var _len = arguments.length, a = Array(_len > 1 ? _len - 1 : 0),
_key = 1; _key < _len; _key++) {
a[_key - 1] = arguments[_key];
}
function foo2() {
var b = arguments.length <= 0 || arguments[0] === undefined ? a :
arguments[0];
assert.equal(b, 1);
}
foo2(undefined, 2);
```
And if you tried to reference any index or `#length`, it’d blow up and
refuse to transpile.
* 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
When using a default param + some destructuring param + a rest param, the
initialization order of the destructured arguments was incorrect due to the
presence of the rest parameter.
