[wyager]

Not sure I agree with you on that, but monads handle your concern nicely. For example, I can write some code that does some database operations, and by parameterizing the code over the type of database actions, my code doesn't care if it's calling a "real" database action or a "fake" one for testing or whatever. That is, the code is completely agnostic as to the implementation details, but we still have full visibility and static checking when we actually run the database code, because we have to specify which database implementation we want to use. Boom, statically verified dependency injection.