Hans Musgrave

The problem seems to be the recursive reference to the `@Frame(...)` type. As a partial workaround for now, you can use `@asyncCall` in enough places to break any `@Frame`-type cycles...

> @ianwilliamson do you have a use case for eig derivatives? Would be useful to know a bit about it. Just in case this is helpful, I've never actually had...

> However, this gauge is usually not important for the calculation of interested quantities (expectation values) because it gets multiplied out This is my experience as well. I've only ever...

> Instead, we need higher level auto-diff primitives, corresponding to well defined functions that are invariant of gauge. That makes sense. Do you think it's still reasonable to support eigenvalue...