Parses invalid yield in for-in statement

[ghost]

When a yield (@mikesherov ) appears within the Initializer of an AssignmentElement outside of a generator function body, it behaves as an IdentifierReference. (For..in statement)

Steps to reproduce

esprima.parse('for ([ x = yield ] in [[]]) ;')

Expected output

Should throw

Actual output

Parses invalid AST