Notation "{ ? x | P }" := {? x : _ | P}
  (at level 0, x at level 99, format  "{ ?  x  |  P }") : type_scope.Definition InjEqMixin f_inj := EqMixin (inj_eqAxiom f_inj).Definition PcanEqMixin g (fK : pcancel f g) := InjEqMixin (pcan_inj fK).Definition CanEqMixin g (fK : cancel f g) := InjEqMixin (can_inj fK).

Lemma val_eqP : ev_ax sT val.