I've read a bit on type invalidation and I know it's a hard problem (in fact it's hard for me to even wrap my head around it, lol). Still, it's unfortunate. One thing I would like to know is if the difficulties with invalidation are a symptom of the dynamic semantics, or of the compilation model.

Namedtuples are cool, but I'm not sure I understand the tradeoffs between using them and using structs. Can I just replace all structs in my project with named tuples, without having a performance hit?