Library Coq.Classes.Init
Tactic Notation "clapply" ident(c) :=
eapply @c ; typeclasses eauto.
Hints for the proof search: these combinators should be considered rigid.
The unconvertible typeclass, to test that two objects of the same type are
actually different.
Class Unconvertible (A : Type) (a b : A).
Ltac unconvertible :=
match goal with
| |- @Unconvertible _ ?x ?y => unify x y with typeclass_instances ; fail 1 "Convertible"
| |- _ => eapply Build_Unconvertible
end.
Hint Extern 0 (@Unconvertible _ _ _) => unconvertible : typeclass_instances.