Haskell doesn't encourage runtime polymorphic module boundaries. That's the key difference with Java, not hierarchies. Abstractions invoked through runtime poly

Haskell doesn't encourage runtime polymorphic module boundaries. That's the key difference with Java, not hierarchies. Abstractions invoked through runtime polymorphic interfaces compose poorly with statically typed exception specifications. Generic composition that lets error types flow through abstractions also lets implementation details flow through, so it is an architectural choice, make no mistake. You don't dodge the tradeoff between abstraction and error handling.