[WIP] Make merge typestable

[davidanthoff]

This doesn't work and it is probably because I'm misusing generated functions once again, but I don't really understand why this is not working. The way I think this should work is this:

using NamedTuples

A = @NT(a=2)
B = @NT(b=2)

merge(A,B)

I get an error message "ERROR: eval cannot be used in a generated function" from that. But, as far as I can tell I'm actually not calling eval in the generated function, all I'm doing is I'm returning a quoted expression that has a macrocall to @NT in it. Now the @NT macro calls eval (sometimes), so I assume that is the problem? Any other ideas for this situation?

@JeffBezanson @vtjnash @shashi

[shashi]

the @NT macro calls eval (sometimes)

Exactly. It's ok to use @NT in a @generated function if the type already exists (because then it won't call eval), but not ok to use it in the merge case where unless you're merging 2 types of the same fields, the output type is a new type. As you stated in #27 this can be fixed by . overloading, or by making named tuples a more primitive Base feature like Tuple.