conv =>
  congr
  . rfl
  . rfl
  . rw [←construct_destruct x]
  . rw [←construct_destruct x]
case a.refl
C : _root_.Container
R : Type u₁
x : Free C R
⊢ equivF Eq ((fun x y => x = y) ⊔ pequiv Eq fun x y => x = y) x x
case a.refl
C : _root_.Container
R : Type u₁
x : Free C R
⊢ equivF Eq ((fun x y => x = y) ⊔ pequiv Eq fun x y => x = y) (construct (destruct x)) (construct (destruct x))