Record dynamic : Type := dyn {typ : Type; val : typ}.Record dynamic : Type := dyn {typ : Type; val : typ}.Record dynamic : Type := dyn {typ : Type; val : typ}.Record dynamic : Type := dyn {typ : Type; val : typ}.Notation dynamic := Dyn.dynamic.Notation dyn := Dyn.dyn.

Lemma eqc A (x : T A) (pf : A = A) : coerce x pf = x.