Fix for Coq 8.8

theories/LocalBlockchain.v

@@ -362,7 +362,7 @@ Definition validate_header (header : BlockHeader) (chain : Chain) : option unit
        && (current_slot chain <? block_slot header)
        && (finalized_height chain <=? block_finalized_height header)
        && (block_finalized_height header <? block_height header)
-       && (Bool.eqb (address_is_contract (block_creator header)) false)
+       && negb (address_is_contract (block_creator header))
        && (block_reward header >=? 0)%Z
   then Some tt
   else None.
@@ -378,9 +378,11 @@ Proof.
     | [H: context[Nat.eqb ?a ?b] |- _] => destruct (Nat.eqb_spec a b)
     | [H: context[Nat.ltb ?a ?b] |- _] => destruct (Nat.ltb_spec a b)
     | [H: context[Nat.leb ?a ?b] |- _] => destruct (Nat.leb_spec a b)
-    | [H: context[Bool.eqb ?a ?b] |- _] => destruct (Bool.eqb_spec a b)
     | [H: context[Z.geb ?a ?b] |- _] => destruct (Z.geb_spec a b)
     end; [|repeat rewrite Bool.andb_false_r in valid; cbn in valid; congruence]).
+  destruct (negb (address_is_contract (block_creator header))) eqn:to_acc;
+    [|cbn in valid; congruence].
+  apply Bool.negb_true_iff in to_acc.
   apply build_is_valid_next_block; cbn; auto.
   lia.
 Qed.