2 ms·

What languages let the user do this?

• neolog 6y ago
  Python's zope.interface can do it. Julia's still figuring out their trait system, but some implementations allow that. I don't know Clojure but I wouldn't be surprised to hear if their Spec allows it.
  • morelisp 6y ago
    I don't think either zope.interface or spec is really thought of as a nominal typing system? Certainly not spec. zope.interface of course can late-bind classes to interfaces but only because it's actually a runtime thing and Python late-binds everything.