So, I was reading the new Flow type strictness and noticed
https://flow.org/blog/2017/05/07/Strict-Function-Call-Arity/
Specifically, I wondered whether the `sum_all` example would copy the
arguments into an array, then loop over. Sadly, it does.
```js
function sum_all(...rest) {
let ret = 0;
for (let i = 0; i < rest.length; i++) { ret += rest[i]; }
return ret;
}
// output
function sum_all() {
var ret = 0;
for (var _len = arguments.length, rest = Array(_len), _key = 0; _key < _len; _key++) {
rest[_key] = arguments[_key];
}
for (var i = 0; i < rest.length; i++) { ret += rest[i]; }
return ret;
}
```
But then I noticed if I changed `let i = 0` to `let i: number = 0`, it
worked directly on `arguments`. That lead me down a rabbit hole to
`Path#_guessExecutionStatusRelativeTo`. When tracing through, the last
comparison made no sense to me. It was trying to find the index of
`"init"` in a list of `["declarations"]` and `"body"` in `["directives",
"body"]`. Red flags and such.
But it makes sense when you're trying to compare the visitor order of
the common ancestor path. Then we're trying to find `"init"` in a list
of `["init", "test", "update", "body"]`. Oh, and there's `"body"` in
there too! And now we know the `ForStatement`'s `init` is executed
before the `body`.
* Use first binding for multiple var declarations
Since var declarations after initial binding have no effect, use the
first declaration. Fixes#2378
* Include hoisted function bindings
* Missing newline in expected.js
* Simplify constantViolations in new Binding on existing
* clarify comment language
* Additional testcase and require->import refactorings
* Removed duplicated getStatementParent function. Refactored all babel-traverse tests to use ESmodules
* 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.
Remove imports to lodash/assign and replace assign with Object.assign.
The lodash/assign is unnecessary for babel 7 as node >4 has the same
functionality built-in with Object.assign as used here.
This resolve the [issue 5353](https://github.com/babel/babel/issues/5353)
The PathHoister ignored member references on "this", causing it
to potentially hoist an expression above its function scope.
This patch tells the hoister to watch for "this", and if seen,
mark the nearest non-arrow function scope as the upper limit
for hoistng.
This fixes#4397 and is an alternative to #4787.
