Use checked arithmetic in types and state proc (#1009)

beacon_node/beacon_chain/Cargo.toml

@@ -42,6 +42,7 @@ rand = "0.7.2"
 proto_array_fork_choice = { path = "../../eth2/proto_array_fork_choice" }
 lru = "0.4.3"
 tempfile = "3.1.0"
+safe_arith = { path = "../../eth2/utils/safe_arith" }
 
 [dev-dependencies]
 lazy_static = "1.4.0"

beacon_node/beacon_chain/src/eth1_chain.rs

@@ -45,6 +45,14 @@ pub enum Error {
     ///
     /// The eth1 caches are stale, or a junk value was voted into the chain.
     UnknownPreviousEth1BlockHash,
+    /// An arithmetic error occurred.
+    ArithError(safe_arith::ArithError),
+}
+
+impl From<safe_arith::ArithError> for Error {
+    fn from(e: safe_arith::ArithError) -> Self {
+        Self::ArithError(e)
+    }
 }
 
 #[derive(Encode, Decode, Clone)]
@@ -369,7 +377,7 @@ impl<T: EthSpec, S: Store<T>> Eth1ChainBackend<T, S> for CachingEth1Backend<T, S
         _spec: &ChainSpec,
     ) -> Result<Vec<Deposit>, Error> {
         let deposit_index = state.eth1_deposit_index;
-        let deposit_count = if let Some(new_eth1_data) = get_new_eth1_data(state, eth1_data_vote) {
+        let deposit_count = if let Some(new_eth1_data) = get_new_eth1_data(state, eth1_data_vote)? {
             new_eth1_data.deposit_count
         } else {
             state.eth1_data.deposit_count

beacon_node/genesis/src/eth1_genesis_service.rs

@@ -383,7 +383,8 @@ impl Eth1GenesisService {
                         .map_err(|e| format!("Error whilst processing deposit: {:?}", e))
                 })?;
 
-            process_activations(&mut local_state, spec);
+            process_activations(&mut local_state, spec)
+                .map_err(|e| format!("Error whilst processing activations: {:?}", e))?;
             let is_valid = is_valid_genesis_state(&local_state, spec);
 
             trace!(