Destructuring assignment in generator expressions and array comprehensions

Why does `for ([] in object);` work fine but `[void 0 for ([] in object)]` or `(void 0 for ([] in object))` throw a syntax error for invalid left-hand assignment? For example, I would expect the following code to work, but it doesn't (the assertion isn't even done due to the syntax error): let ( i = 0, iterable = {__iterator__:function() { var i = 5; while (i--) yield i; } } ) { for ([] in iterable) i++; console.assertEquals([void 0 for ([] in iterable)].length, i); }
My guess is that they hit different grammar rules: the first for is NOT a generator (it is a for-statement), while the latter is. It doesn't appear that decomposition is supported in that position.

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