This is a fun one. A type system designed to maximise error diagnostics for the programmer is different to one designed to maximise information conveyed to the

This is a fun one. A type system designed to maximise error diagnostics for the programmer is different to one designed to maximise information conveyed to the compiler. Most people seem to think in terms of the former, which in extreme cases leads to things like typescript where all the information gathered during typechecking is discarded before the underlying javascript takes over.