Definition proj_struct (i : ident) (m : members) {A: ident * type -> Type} (v: compact_prod (map A m)) (d: A (i, field_type i m)): A (i, field_type i m) :=
  proj_compact_prod (i, field_type i m) m v d member_dec.Definition proj_union (i : ident) (m : members) {A: ident * type -> Type} (v: compact_sum (map A m)) (d: A (i, field_type i m)): A (i, field_type i m) :=
  proj_compact_sum (i, field_type i m) m v d member_dec.Definition members_union_inj {m: members} {A} (v: compact_sum (map A m)) (it: ident * type): Prop :=
  compact_sum_inj v it member_dec.Definition upd_sublist {X: Type} (lo hi: Z) (l: list X) (l0: list X) : list X :=
  firstn (Z.to_nat lo) l ++ l0 ++ skipn (Z.to_nat hi) l.(* TODO: We should use the following two definition in replace_refill lemmas in the future. And avoid using compact prod/sum directly. *)

Definition upd_struct (i : ident) (m : members) {A: ident * type -> Type} (v: compact_prod (map A m)) (v0: A (i, field_type i m)): compact_prod (map A m) :=
  upd_compact_prod _ v (i, field_type i m) v0 member_dec.Definition upd_union (i : ident) (m : members) {A: ident * type -> Type} (v: compact_sum (map A m)) (v0: A (i, field_type i m)): compact_sum (map A m) :=
  upd_compact_sum _ v (i, field_type i m) v0 member_dec.

Lemma proj_union_JMeq: forall (i: ident) (m : members) {A1 A2: ident * type -> Type} (v1: compact_sum (map A1 m)) (v2: compact_sum (map A2 m)) (d1: A1 (i, field_type i m)) (d2: A2 (i, field_type i m)), (forall i, in_members i m -> @eq Type (A1 (i, field_type i m)) (A2 (i, field_type i m))) -> members_no_replicate m = true -> members_union_inj v1 (i, field_type i m) -> JMeq v1 v2 -> JMeq (proj_union i m v1 d1) (proj_union i m v2 d2).