validators: better typing to avoid casting

packages/testing/src/consensus_testing/test_fixtures/fork_choice.py

@@ -316,7 +316,7 @@ def _build_block_from_spec(
         """
         # Determine proposer index
         proposer_index = spec.proposer_index or Uint64(
-            int(spec.slot) % store.states[store.head].validators.count
+            int(spec.slot) % len(store.states[store.head].validators)
         )
 
         # Resolve parent root from label or default to head

packages/testing/src/consensus_testing/test_fixtures/state_transition.py

@@ -195,7 +195,7 @@ def _build_block_from_spec(self, spec: BlockSpec, state: State) -> tuple[Block,
             Block and cached post-state (None if not computed).
         """
         # Use provided proposer index or compute it
-        proposer_index = spec.proposer_index or Uint64(int(spec.slot) % int(state.validators.count))
+        proposer_index = spec.proposer_index or Uint64(int(spec.slot) % len(state.validators))
 
         # Use provided parent root or compute it
         if spec.parent_root is not None:

packages/testing/src/consensus_testing/test_fixtures/verify_signatures.py

@@ -185,7 +185,7 @@ def _build_block_from_spec(
             A complete signed block with all attestations.
         """
         # Determine proposer index
-        proposer_index = spec.proposer_index or Uint64(int(spec.slot) % int(state.validators.count))
+        proposer_index = spec.proposer_index or Uint64(int(spec.slot) % len(state.validators))
 
         # Resolve parent root
         parent_state = state.process_slots(spec.slot)

packages/testing/src/consensus_testing/test_types/state_expectation.py

@@ -147,7 +147,7 @@ def validate_against_state(self, state: "State") -> None:
                     )
 
             elif field_name == "validator_count":
-                actual_count = state.validators.count
+                actual_count = len(state.validators)
                 if actual_count != expected_value:
                     raise AssertionError(
                         f"State validation failed: validator_count = {actual_count}, "

src/lean_spec/subspecs/containers/block/block.py

@@ -9,15 +9,14 @@
 can propose.
 """
 
-from typing import TYPE_CHECKING, cast
+from typing import TYPE_CHECKING
 
 from lean_spec.subspecs.containers.slot import Slot
 from lean_spec.types import Bytes32, Uint64
 from lean_spec.types.container import Container
 
 from ...xmss.containers import Signature as XmssSignature
 from ..attestation import Attestation
-from ..validator import Validator
 from .types import (
     AggregatedAttestations,
     AttestationSignatures,
@@ -184,7 +183,7 @@ def verify_signatures(self, parent_state: "State") -> bool:
             for validator_id, signature in zip(validator_ids, aggregated_signature, strict=True):
                 # Ensure validator exists in the active set
                 assert validator_id < Uint64(len(validators)), "Validator index out of range"
-                validator = cast(Validator, validators[validator_id])
+                validator = validators[validator_id]
 
                 assert signature.verify(
                     validator.get_pubkey(),
@@ -198,7 +197,7 @@ def verify_signatures(self, parent_state: "State") -> bool:
         assert proposer_attestation.validator_id < Uint64(len(validators)), (
             "Proposer index out of range"
         )
-        proposer = cast(Validator, validators[proposer_attestation.validator_id])
+        proposer = validators[proposer_attestation.validator_id]
 
         assert proposer_signature.verify(
             proposer.get_pubkey(),

src/lean_spec/subspecs/containers/state/state.py

@@ -242,7 +242,7 @@ def process_block_header(self, block: Block) -> "State":
         assert is_proposer(
             validator_index=block.proposer_index,
             slot=self.slot,
-            num_validators=Uint64(self.validators.count),
+            num_validators=Uint64(len(self.validators)),
         ), "Incorrect block proposer"
 
         # Verify the chain link.
@@ -426,7 +426,7 @@ def process_attestations(
         justifications = (
             {
                 root: self.justifications_validators[
-                    i * self.validators.count : (i + 1) * self.validators.count
+                    i * len(self.validators) : (i + 1) * len(self.validators)
                 ]
                 for i, root in enumerate(self.justifications_roots)
             }
@@ -505,7 +505,7 @@ def process_attestations(
             # If this is the first vote for the target block, create a fresh tally sheet:
             # - one boolean per validator, all initially False.
             if target.root not in justifications:
-                justifications[target.root] = [Boolean(False)] * self.validators.count
+                justifications[target.root] = [Boolean(False)] * len(self.validators)
 
             # Mark that this validator has voted for the target.
             #
@@ -524,7 +524,7 @@ def process_attestations(
             # 3 * (number of votes) ≥ 2 * (total validators)
             count = sum(bool(justified) for justified in justifications[target.root])
 
-            if 3 * count >= (2 * self.validators.count):
+            if 3 * count >= (2 * len(self.validators)):
                 # The block becomes justified
                 #
                 # The chain now considers this block part of its safe head.

src/lean_spec/subspecs/containers/state/types.py

@@ -39,7 +39,8 @@ class Validators(SSZList):
     ELEMENT_TYPE = Validator
     LIMIT = int(DEVNET_CONFIG.validator_registry_limit)
 
-    @property
-    def count(self) -> int:
-        """Return the number of validators in the registry."""
-        return len(self.data)
+    def __getitem__(self, index: int) -> Validator:
+        """Access a validator by index with proper typing."""
+        item = self.data[index]
+        assert isinstance(item, Validator)
+        return item

src/lean_spec/subspecs/forkchoice/store.py

@@ -690,7 +690,7 @@ def update_safe_target(self) -> "Store":
         """
         # Get validator count from head state
         head_state = self.states[self.head]
-        num_validators = head_state.validators.count
+        num_validators = len(head_state.validators)
 
         # Calculate 2/3 majority threshold (ceiling division)
         min_target_score = -(-num_validators * 2 // 3)
@@ -967,7 +967,7 @@ def produce_block_with_signatures(
         head_state = store.states[head_root]
 
         # Validate proposer authorization for this slot
-        num_validators = Uint64(head_state.validators.count)
+        num_validators = Uint64(len(head_state.validators))
         assert is_proposer(validator_index, slot, num_validators), (
             f"Validator {validator_index} is not the proposer for slot {slot}"
         )

tests/lean_spec/subspecs/forkchoice/test_validator.py

@@ -643,7 +643,7 @@ def test_validator_operations_invalid_parameters(self, sample_store: Store) -> N
         # Get the state to determine number of validators
         genesis_hash = sample_store.head
         state = sample_store.states[genesis_hash]
-        num_validators = Uint64(state.validators.count)
+        num_validators = Uint64(len(state.validators))
 
         # is_proposer should work (though likely return False)
         result = is_proposer(large_validator, large_slot, num_validators)