MPS has a thing where mistakes written in the DSL are caught in the implementation layer and then translated back into terms related to the DSL before they're r

MPS has a thing where mistakes written in the DSL are caught in the implementation layer and then translated back into terms related to the DSL before they're reported to the programmer. Looked good in a talk one of their developers gives. I'd have written this off as "can't be done" without that existence proof.