Add stubbed-out block processing to fork choice

eth2/lmd_ghost/src/lib.rs

@@ -9,18 +9,27 @@ pub use reduced_tree::ThreadSafeReducedTree;
 pub type Result<T> = std::result::Result<T, String>;
 
 pub trait LmdGhost<S: Store, E: EthSpec>: Send + Sync {
-    fn new(store: Arc<S>, genesis_root: Hash256) -> Self;
+    /// Create a new instance, with the given `store` and `finalized_root`.
+    fn new(store: Arc<S>, finalized_root: Hash256) -> Self;
 
-    fn process_message(
+    /// Process an attestation message from some validator that attests to some `block_hash`
+    /// representing a block at some `block_slot`.
+    fn process_attestation(
         &self,
         validator_index: usize,
         block_hash: Hash256,
         block_slot: Slot,
     ) -> Result<()>;
 
+    /// Process a block that was seen on the network.
+    fn process_block(&self, block_hash: Hash256, block_slot: Slot) -> Result<()>;
+
+    /// Returns the head of the chain, starting the search at `start_block_root` and moving upwards
+    /// (in block height).
     fn find_head<F>(&self, start_block_root: Hash256, weight: F) -> Result<Hash256>
     where
         F: Fn(usize) -> Option<u64> + Copy;
 
-    fn update_finalized_root(&self, new_root: Hash256) -> Result<()>;
+    /// Provide an indication that the blockchain has been finalized at the given `finalized_root`.
+    fn update_finalized_root(&self, finalized_root: Hash256) -> Result<()>;
 }

eth2/lmd_ghost/src/reduced_tree.rs

@@ -40,7 +40,7 @@ where
         }
     }
 
-    fn process_message(
+    fn process_attestation(
         &self,
         validator_index: usize,
         block_hash: Hash256,
@@ -52,6 +52,11 @@ where
             .map_err(Into::into)
     }
 
+    /// Process a block that was seen on the network.
+    fn process_block(&self, block_hash: Hash256, block_slot: Slot) -> SuperResult<()> {
+        unimplemented!();
+    }
+
     fn find_head<F>(&self, start_block_root: Hash256, weight_fn: F) -> SuperResult<Hash256>
     where
         F: Fn(usize) -> Option<u64> + Copy,