lazy evaluation of dicts

[sanderr]

Lazy evaluation of dicts would be very useful for passing kwarg dicts to constructors. Currently, the constructor statement needs to wait for all dict values before it can begin execution. With lazy evaluation we would only need to wait on the keys (and index values).

What's meant by lazy evaluation? Evaluate to Dict[str, ExpressionStatement] instead of to Dict[str, Type]

Related to #1711, #620 and #1702

[wouterdb]

the easiest way of doing this might be to make them into Instances, so that lookup in a dictionary becomes an attribute reference.

[sanderr]

I agree, I was thinking something along these lines as well.