> For example, `Either[T, Either[FileNotFoundCheckedException, RuntimeException]]` is basically isomorphic to a function that returns T or throws and has the sa

> For example, `Either[T, Either[FileNotFoundCheckedException, RuntimeException]]` is basically isomorphic to a function that returns T or throws and has the same monad support, but can still force the developer to handle the checked exceptions. Yes, and I tend to write my code this way (although I find right-biased 'Either' a bit cleaner). The problem is (a) the mountain of JVM code which uses checked exceptions instead plus (b) the Scala compiler completely ignoring that exception information. Solving (a) is unrealistic, but (b) is an entirely self-imposed decision by the Scala developers. Their type checker could have incorporated checked exceptions in exactly the way you describe, and I wouldn't have any complaints (about exceptions, at least... null is a whole different beast ;) )