merge in fork choice. tests pass

specs/core/0_beacon-chain.md

@@ -1337,13 +1337,14 @@ def process_justification_and_finalization(state: BeaconState) -> None:
         state, get_matching_target_attestations(state, previous_epoch)
     )
     if previous_epoch_matching_target_balance * 3 >= get_total_active_balance(state) * 2:
-        state.current_justified_checkpoint = Checkpoint(previous_epoch, get_block_root(state, previous_epoch))
+        state.current_justified_checkpoint = Checkpoint(epoch=previous_epoch,
+                                                        root=get_block_root(state, previous_epoch))
         state.justification_bitfield |= (1 << 1)
     current_epoch_matching_target_balance = get_attesting_balance(
         state, get_matching_target_attestations(state, current_epoch)
     )
     if current_epoch_matching_target_balance * 3 >= get_total_active_balance(state) * 2:
-        state.current_justified_checkpoint = Checkpoint(current_epoch, get_block_root(state, current_epoch))
+        state.current_justified_checkpoint = Checkpoint(epoch=current_epoch, root=get_block_root(state, current_epoch))
         state.justification_bitfield |= (1 << 0)
 
     # Process finalizations

specs/core/0_fork-choice.md

@@ -55,15 +55,6 @@ The head block root associated with a `store` is defined as `get_head(store)`. A
 
 ### Helpers
 
-#### `Checkpoint`
-
-```python
-@dataclass(eq=True, frozen=True)
-class Checkpoint(object):
-    epoch: Epoch
-    root: Hash
-```
-
 #### `Store`
 
 ```python
@@ -84,8 +75,8 @@ class Store(object):
 def get_genesis_store(genesis_state: BeaconState) -> Store:
     genesis_block = BeaconBlock(state_root=hash_tree_root(genesis_state))
     root = signing_root(genesis_block)
-    justified_checkpoint = Checkpoint(GENESIS_EPOCH, root)
-    finalized_checkpoint = Checkpoint(GENESIS_EPOCH, root)
+    justified_checkpoint = Checkpoint(epoch=GENESIS_EPOCH, root=root)
+    finalized_checkpoint = Checkpoint(epoch=GENESIS_EPOCH, root=root)
     return Store(
         time=genesis_state.genesis_time,
         justified_checkpoint=justified_checkpoint,
@@ -168,21 +159,21 @@ def on_block(store: Store, block: BeaconBlock) -> None:
     store.block_states[signing_root(block)] = state
 
     # Update justified checkpoint
-    if state.current_justified_epoch > store.justified_checkpoint.epoch:
-        store.justified_checkpoint = Checkpoint(state.current_justified_epoch, state.current_justified_root)
-    elif state.previous_justified_epoch > store.justified_checkpoint.epoch:
-        store.justified_checkpoint = Checkpoint(state.previous_justified_epoch, state.previous_justified_root)
+    if state.current_justified_checkpoint.epoch > store.justified_checkpoint.epoch:
+        store.justified_checkpoint = state.current_justified_checkpoint
+    elif state.previous_justified_checkpoint.epoch > store.justified_checkpoint.epoch:
+        store.justified_checkpoint = state.previous_justified_checkpoint
 
     # Update finalized checkpoint
-    if state.finalized_epoch > state.finalized_epoch:
-        store.finalized_checkpoint = Checkpoint(state.finalized_epoch, state.finalized_root)
+    if state.finalized_checkpoint.epoch > store.finalized_checkpoint.epoch:
+        store.finalized_checkpoint = state.finalized_checkpoint
 ```
 
 #### `on_attestation`
 
 ```python
 def on_attestation(store: Store, attestation: Attestation) -> None:
-    target = Checkpoint(attestation.data.target_epoch, attestation.data.target_root)
+    target = attestation.data.target
 
     # Cannot calculate the current shuffling if have not seen the target
     assert target.root in store.blocks

test_libs/pyspec/eth2spec/test/fork_choice/test_on_attestation.py

@@ -21,8 +21,8 @@ def run_on_attestation(spec, state, store, attestation, valid=True):
     assert (
         store.latest_targets[indexed_attestation.custody_bit_0_indices[0]] ==
         spec.Checkpoint(
-            epoch=attestation.data.target_epoch,
-            root=attestation.data.target_root,
+            epoch=attestation.data.target.epoch,
+            root=attestation.data.target.root,
         )
     )