That makes no sense. RPython is not a general-purpose development language, it's a strict subset of Python for writing VMs. From what I understand Crystal aims to be a general-purpose statically-typed native-compiled language with a syntax similar to Ruby in much the way Nim aims to be a general-purpose statically-typed native-compiled language with a syntax similar to Python.
Neither Nim nor Crystal exist solely to write VMs and auto-implement JITs, and programs in neither is expected to run unmodified on a VM for the inspiration language.
