From b648375bbe0749c3906d70f922cff091b21c9ab1 Mon Sep 17 00:00:00 2001
From: teor <teor@riseup.net>
Date: Thu, 16 Jul 2020 13:59:44 +1000
Subject: [PATCH] fix: Hard-code the genesis previous block hash

---
 zebra-consensus/src/checkpoint.rs |  6 +-----
 zebra-consensus/src/parameters.rs | 15 +++++----------
 2 files changed, 6 insertions(+), 15 deletions(-)

diff --git a/zebra-consensus/src/checkpoint.rs b/zebra-consensus/src/checkpoint.rs
index 7de82be84..587ac7b49 100644
--- a/zebra-consensus/src/checkpoint.rs
+++ b/zebra-consensus/src/checkpoint.rs
@@ -85,9 +85,6 @@ pub const MAX_QUEUED_BLOCKS_PER_HEIGHT: usize = 4;
 struct CheckpointVerifier {
     // Inputs
     //
-    /// The network for this verifier.
-    network: Network,
-
     /// The checkpoint list for this verifier.
     checkpoint_list: CheckpointList,
 
@@ -130,7 +127,6 @@ impl CheckpointVerifier {
         checkpoint_list: impl IntoIterator<Item = (BlockHeight, BlockHeaderHash)>,
     ) -> Result<Self, Error> {
         Ok(CheckpointVerifier {
-            network,
             checkpoint_list: CheckpointList::new(network, checkpoint_list)?,
             queued: BTreeMap::new(),
             // We start by verifying the genesis block, by itself
@@ -422,7 +418,7 @@ impl CheckpointVerifier {
             // Since genesis blocks are hard-coded in zcashd, and not verified
             // like other blocks, the genesis parent hash is set by the
             // consensus parameters.
-            BeforeGenesis => parameters::genesis_previous_block_hash(self.network),
+            BeforeGenesis => parameters::GENESIS_PREVIOUS_BLOCK_HASH,
             PreviousCheckpoint(hash) => hash,
             FinalCheckpoint => return,
         };
diff --git a/zebra-consensus/src/parameters.rs b/zebra-consensus/src/parameters.rs
index 488cfdcb7..53391a70a 100644
--- a/zebra-consensus/src/parameters.rs
+++ b/zebra-consensus/src/parameters.rs
@@ -12,16 +12,11 @@
 use zebra_chain::block::BlockHeaderHash;
 use zebra_chain::{Network, Network::*};
 
-/// Returns the previous block hash for the genesis block in `network`.
-pub fn genesis_previous_block_hash(network: Network) -> BlockHeaderHash {
-    // All current networks use all-zeroes for the parent of the genesis block.
-    // (In Bitcoin, `null` is `[0; 32]`.)
-    //
-    // TODO: make this function const when feature(const_if_match) stabilises.
-    match network {
-        Mainnet | Testnet => BlockHeaderHash([0; 32]),
-    }
-}
+/// The previous block hash for the genesis block.
+///
+/// All known networks use the Bitcoin `null` value for the parent of the
+/// genesis block. (In Bitcoin, `null` is `[0; 32]`.)
+pub const GENESIS_PREVIOUS_BLOCK_HASH: BlockHeaderHash = BlockHeaderHash([0; 32]);
 
 /// Returns the hash for the genesis block in `network`.
 pub fn genesis_hash(network: Network) -> BlockHeaderHash {