Huh, interesting... trying to look at that from the perspective of straight.plugin to be general. If you have a set of plugins, and you want to say "One of these provides a foo() method, call it with these args" and error if it finds more than one. Do you really think that makes sense? That's sort of what first() was for, but the idea being you can have multiples, and we would provide a way to configure which plugin to prefer. This allows a user to override something. You think a straight out error is better?