Set Bullet Behavior "Strict Subproofs".
Opaque upto.

Lemma make_shares_ext' : forall i d l l' lgood shs (Hlen : Zlength l = Zlength l')
(Hi : forall j, 0 <= j < Zlength l -> Znth j lgood false = true -> Znth j l d = i <-> Znth j l' d = i),
make_shares shs (combine lgood l) i = make_shares shs (combine lgood l') i.