I still can't see a reference to Cython in the PEP. Larry, I don't really mind adding a newly designed DSL for this, but regarding the implementation of the actual argument parser, could you at least add a short paragraph to the PEP that mentions it as worth being looked at? I mean, it already does all of this and generates optimised and streamlined code for fast unpacking of args and kwargs, although just from a typed Python function signature, not a full fledged DSL. I mean, you don't have to reuse that code, but it's certainly relevant to see how others have solved this. Years ago.