Make BeaconState.balances a tree list!

beacon_node/beacon_chain/src/beacon_fork_choice_store.rs

@@ -217,12 +217,13 @@ where
         };
         let finalized_checkpoint = justified_checkpoint;
 
+        // FIXME(sproul): avoid `to_vec` perf penalty
         Self {
             store,
             balances_cache: <_>::default(),
             time: anchor_state.slot(),
             justified_checkpoint,
-            justified_balances: anchor_state.balances().clone().into(),
+            justified_balances: anchor_state.balances().to_vec(),
             finalized_checkpoint,
             best_justified_checkpoint: justified_checkpoint,
             _phantom: PhantomData,
@@ -327,8 +328,7 @@ where
                 .map_err(Error::FailedToReadState)?
                 .ok_or_else(|| Error::MissingState(justified_block.state_root()))?
                 .balances()
-                .clone()
-                .into();
+                .to_vec();
         }
 
         Ok(())

beacon_node/store/Cargo.toml

@@ -25,6 +25,7 @@ lighthouse_metrics = { path = "../../common/lighthouse_metrics" }
 lru = "0.6.0"
 sloggers = "2.0.2"
 directory = { path = "../../common/directory" }
+tree_hash = "0.4.0"
 
 [features]
 milhouse = ["state_processing/milhouse"]

beacon_node/store/src/chunked_vector.rs

@@ -17,6 +17,7 @@
 use self::UpdatePattern::*;
 use crate::*;
 use ssz::{Decode, Encode};
+use tree_hash::TreeHash;
 use typenum::Unsigned;
 use types::VList;
 
@@ -56,7 +57,7 @@ pub trait Field<E: EthSpec>: Copy {
     /// The type of value stored in this field: the `T` from `FixedVector<T, N>`.
     ///
     /// The `Default` impl will be used to fill extra vector entries.
-    type Value: Decode + Encode + Default + Clone + PartialEq + std::fmt::Debug;
+    type Value: TreeHash + Decode + Encode + Default + Clone + PartialEq + std::fmt::Debug;
 
     /// The length of this field: the `N` from `FixedVector<T, N>`.
     type Length: Unsigned;

beacon_node/store/src/partial_beacon_state.rs

@@ -48,7 +48,7 @@ where
 
     // Registry
     pub validators: VList<Validator, T::ValidatorRegistryLimit>,
-    pub balances: VariableList<u64, T::ValidatorRegistryLimit>,
+    pub balances: VList<u64, T::ValidatorRegistryLimit>,
 
     // Shuffling
     /// Randao value from the current slot, for patching into the per-epoch randao vector.