[...arguments] should not compile to return [].concat(arguments)

Because Array#concat will recognize arguments object as a plain object instead of an array. This issue is also reproducible with other array-like objects, such as NodeList.

How other transpilers handle this:

Babel:

[].concat(Array.prototype.slice.call(arguments));

TypeScript:

arguments.slice()
// Error: (1/1) Type 'IArguments' is not an array type.

Traceur:

$traceurRuntime.spread(arguments);