> I've never understood why. No parametric polymorphism in exception specifications. Like if you have a record parser that invokes a user-defined callback for

> I've never understood why. No parametric polymorphism in exception specifications. Like if you have a record parser that invokes a user-defined callback for each record, then you literally can’t type it in such a way as to allow the callback to throw exceptions (that the caller is presumably prepared to handle, having provided the callback in the first place). To be clear, this is not simple. It seems to me like it’ll quickly go into full-blown effect typing territory, which is still not completely solved today and was in an absolutely embryonic state in the early 2000s.