Man, I haven't done structural inheritance in years and by now, this reads like the ramblings of a mad person.

Like, I recently had a use-case, where I actually wanted to define multiple types with the same fields and for various reasons ended up using a macro for that.
And that still felt simpler than whatever is going on in this article, because there were no cross-relationships between the types at runtime. The macro templated the type definitions as if I had copy-pasted them, except there's no actual code duplication, which is ultimately all I wanted.