Opaque member_dec.

Lemma compact_sum_inj_eq_spec: forall {A} a0 a1 (l: list A) F0 F1 (v0: compact_sum (map F0 (a0 :: a1 :: l))) (v1: compact_sum (map F1 (a0 :: a1 :: l))) H,
~ In a0 (a1 :: l) ->
((forall a, compact_sum_inj v0 a H <-> compact_sum_inj v1 a H) <->
match v0, v1 with
| inl _, inl _ => True
| inr v0, inr v1 => forall a, compact_sum_inj (v0: compact_sum (map F0 (a1 :: l))) a H <-> compact_sum_inj (v1: compact_sum (map F1 (a1 :: l))) a H
| _, _ => False
end).