good error/failure framework: - should be obvious which functions can fail and what errors they can fail with - propogating an error up the stack should be vi

good error/failure framework: - should be obvious which functions can fail and what errors they can fail with - propogating an error up the stack should be visible in the code and semantically easy to do - errors should be composable and easy to add additional information to - deciding to not handle a error should be explicit and otherwise produce a warning - errors should be fast and cheap to return errors - (maybe nice to have) ability for a function to have and return multiple errors