This looks like a good idea:

https://errors.haskell.org/

https://github.com/haskellfoundation/error-message-index

They are trying to make baffling error messages intelligible by
providing examples and explaining some background.

Maybe we should establish errors.scheme.org at some point. Just noting
this down for the future.

My favorite Scheme error message is "Operator is not a procedure". I
nominate it as our equivalent of Unix's infamous "Invalid argument". In
both cases, the root cause can be pretty much anything.