Use proper types when dealing with LC Merkle proofs

specs/altair/light-client/full-node.md

@@ -75,7 +75,8 @@ def create_light_client_bootstrap(state: BeaconState,
     return LightClientBootstrap(
         header=block_to_light_client_header(block),
         current_sync_committee=state.current_sync_committee,
-        current_sync_committee_branch=compute_merkle_proof(state, CURRENT_SYNC_COMMITTEE_INDEX),
+        current_sync_committee_branch=CurrentSyncCommitteeBranch(
+            compute_merkle_proof(state, CURRENT_SYNC_COMMITTEE_INDEX)),
     )
 ```
 
@@ -122,7 +123,8 @@ def create_light_client_update(state: BeaconState,
     # `next_sync_committee` is only useful if the message is signed by the current sync committee
     if update_attested_period == update_signature_period:
         update.next_sync_committee = attested_state.next_sync_committee
-        update.next_sync_committee_branch = compute_merkle_proof(attested_state, NEXT_SYNC_COMMITTEE_INDEX)
+        update.next_sync_committee_branch = NextSyncCommitteeBranch(
+            compute_merkle_proof(attested_state, NEXT_SYNC_COMMITTEE_INDEX))
 
     # Indicate finality whenever possible
     if finalized_block is not None:
@@ -131,7 +133,8 @@ def create_light_client_update(state: BeaconState,
             assert hash_tree_root(update.finalized_header.beacon) == attested_state.finalized_checkpoint.root
         else:
             assert attested_state.finalized_checkpoint.root == Bytes32()
-        update.finality_branch = compute_merkle_proof(attested_state, FINALIZED_ROOT_INDEX)
+        update.finality_branch = FinalityBranch(
+            compute_merkle_proof(attested_state, FINALIZED_ROOT_INDEX))
 
     update.sync_aggregate = block.message.body.sync_aggregate
     update.signature_slot = block.message.slot

specs/altair/light-client/sync-protocol.md

@@ -82,7 +82,7 @@ Additional documents describe how the light client sync protocol can be used:
 ### `FinalityBranch`
 
 ```python
-class FinalityBranch(Vector[Bytes32, floorlog2(FINALIZED_ROOT_INDEX)]):
+class FinalityBranch(Vector[Bytes32, floorlog2(FINALIZED_ROOT_INDEX)]):  
     pass
 ```
 
@@ -201,14 +201,14 @@ def is_valid_light_client_header(header: LightClientHeader) -> bool:
 
 ```python
 def is_sync_committee_update(update: LightClientUpdate) -> bool:
-    return update.next_sync_committee_branch != [Bytes32() for _ in range(floorlog2(NEXT_SYNC_COMMITTEE_INDEX))]
+    return update.next_sync_committee_branch != NextSyncCommitteeBranch()
 ```
 
 ### `is_finality_update`
 
 ```python
 def is_finality_update(update: LightClientUpdate) -> bool:
-    return update.finality_branch != [Bytes32() for _ in range(floorlog2(FINALIZED_ROOT_INDEX))]
+    return update.finality_branch != FinalityBranch()
 ```
 
 ### `is_better_update`
@@ -520,7 +520,7 @@ def process_light_client_finality_update(store: LightClientStore,
     update = LightClientUpdate(
         attested_header=finality_update.attested_header,
         next_sync_committee=SyncCommittee(),
-        next_sync_committee_branch=[Bytes32() for _ in range(floorlog2(NEXT_SYNC_COMMITTEE_INDEX))],
+        next_sync_committee_branch=NextSyncCommitteeBranch(),
         finalized_header=finality_update.finalized_header,
         finality_branch=finality_update.finality_branch,
         sync_aggregate=finality_update.sync_aggregate,
@@ -539,9 +539,9 @@ def process_light_client_optimistic_update(store: LightClientStore,
     update = LightClientUpdate(
         attested_header=optimistic_update.attested_header,
         next_sync_committee=SyncCommittee(),
-        next_sync_committee_branch=[Bytes32() for _ in range(floorlog2(NEXT_SYNC_COMMITTEE_INDEX))],
+        next_sync_committee_branch=NextSyncCommitteeBranch(),
         finalized_header=LightClientHeader(),
-        finality_branch=[Bytes32() for _ in range(floorlog2(FINALIZED_ROOT_INDEX))],
+        finality_branch=FinalityBranch(),
         sync_aggregate=optimistic_update.sync_aggregate,
         signature_slot=optimistic_update.signature_slot,
     )

specs/capella/light-client/full-node.md

@@ -46,14 +46,15 @@ def block_to_light_client_header(block: SignedBeaconBlock) -> LightClientHeader:
             transactions_root=hash_tree_root(payload.transactions),
             withdrawals_root=hash_tree_root(payload.withdrawals),
         )
-        execution_branch = compute_merkle_proof(block.message.body, EXECUTION_PAYLOAD_INDEX)
+        execution_branch = ExecutionBranch(
+            compute_merkle_proof(block.message.body, EXECUTION_PAYLOAD_INDEX))
     else:
         # Note that during fork transitions, `finalized_header` may still point to earlier forks.
         # While Bellatrix blocks also contain an `ExecutionPayload` (minus `withdrawals_root`),
         # it was not included in the corresponding light client data. To ensure compatibility
         # with legacy data going through `upgrade_lc_header_to_capella`, leave out execution data.
         execution_header = ExecutionPayloadHeader()
-        execution_branch = [Bytes32() for _ in range(floorlog2(EXECUTION_PAYLOAD_INDEX))]
+        execution_branch = ExecutionBranch()
 
     return LightClientHeader(
         beacon=BeaconBlockHeader(

specs/capella/light-client/sync-protocol.md

@@ -41,7 +41,7 @@ Additional documents describes the impact of the upgrade on certain roles:
 ### `ExecutionBranch`
 
 ```python
-class ExecutionBranch(Vector[Bytes32, floorlog2(EXECUTION_PAYLOAD_INDEX)]):
+class ExecutionBranch(Vector[Bytes32, floorlog2(EXECUTION_PAYLOAD_INDEX)]):  
     pass
 ```
 
@@ -81,7 +81,7 @@ def is_valid_light_client_header(header: LightClientHeader) -> bool:
     if epoch < CAPELLA_FORK_EPOCH:
         return (
             header.execution == ExecutionPayloadHeader()
-            and header.execution_branch == [Bytes32() for _ in range(floorlog2(EXECUTION_PAYLOAD_INDEX))]
+            and header.execution_branch == ExecutionBranch()
         )
 
     return is_valid_merkle_branch(

specs/deneb/light-client/full-node.md

@@ -52,14 +52,15 @@ def block_to_light_client_header(block: SignedBeaconBlock) -> LightClientHeader:
             execution_header.blob_gas_used = payload.blob_gas_used
             execution_header.excess_blob_gas = payload.excess_blob_gas
 
-        execution_branch = compute_merkle_proof(block.message.body, EXECUTION_PAYLOAD_INDEX)
+        execution_branch = ExecutionBranch(
+            compute_merkle_proof(block.message.body, EXECUTION_PAYLOAD_INDEX))
     else:
         # Note that during fork transitions, `finalized_header` may still point to earlier forks.
         # While Bellatrix blocks also contain an `ExecutionPayload` (minus `withdrawals_root`),
         # it was not included in the corresponding light client data. To ensure compatibility
         # with legacy data going through `upgrade_lc_header_to_capella`, leave out execution data.
         execution_header = ExecutionPayloadHeader()
-        execution_branch = [Bytes32() for _ in range(floorlog2(EXECUTION_PAYLOAD_INDEX))]
+        execution_branch = ExecutionBranch()
 
     return LightClientHeader(
         beacon=BeaconBlockHeader(

specs/deneb/light-client/sync-protocol.md

@@ -74,7 +74,7 @@ def is_valid_light_client_header(header: LightClientHeader) -> bool:
     if epoch < CAPELLA_FORK_EPOCH:
         return (
             header.execution == ExecutionPayloadHeader()
-            and header.execution_branch == [Bytes32() for _ in range(floorlog2(EXECUTION_PAYLOAD_INDEX))]
+            and header.execution_branch == ExecutionBranch()
         )
 
     return is_valid_merkle_branch(