Unhappy way is a part of contract. So yes, that is what I want. If a function couldn't fail before but can after the update - I want to know about it. In fact,

Unhappy way is a part of contract. So yes, that is what I want. If a function couldn't fail before but can after the update - I want to know about it. In fact, at each layer, if you want to propagate an error, you have to convert it to one specific to that layer.