Default Parameters + Destructuring - Pending items

[0xe]

Address items pending from #1640

• Destructuring with defaults in for loops. This should evaluate to 3, instead throws NPE:

function a() {}; (function() { 
            for (let {x = a()} = {}; ; ) { 
                return 3; 
            }
        })()

• Reading [Symbol.iterator] from default array/object

function f([x = 1, y = 2] = {x: 3, y: 4}) {
 return x + y;
 }

This should throw a TypeError as [Symbol.iterator] is not implemented for that object on the rhs, instead uses defaults to return 3.

function f([x = 1, y = 2] = {x: 3, y: 4, 
                              [Symbol.iterator]: function*() { 
                                yield 3; 
                                yield 4; 
                              }}) {
                                return x + y;
                              }

And this should work because we call into iterator to get the default values. Instead we throw a NPE currently.