[colinmcd]

This is mentioned under "Limitations"

> The result of the macro must be serializable!

> Functions and instances of most classes (except those mentioned above) are not serializable.

[Zambyte]

Well those are both slightly different than "code". I mean something more like returning an S-expression, or a JS AST object, and having that be inlined. That should have no problem with serialization, since it could just be dropped into the AST (unlike a function or class).