Module bt.
Record Equ (A : Type) (R : A -> A -> Prop).
Definition equiv {A} R (e : Equ A R) := R.
Record Refl (A : Type) (R : A -> A -> Prop).
Hint Extern 0 (Refl _ _) => unshelve class_apply @equ_refl; [shelve|] : foo.
Variable R : nat -> nat -> Prop.

Lemma bas : Equ nat R.