more typing fixes

Author: DavidBuchanan314

src/atmst/blockstore/__init__.py

@@ -33,7 +33,7 @@ def del_block(self, key: bytes) -> None:
 
 
 class MemoryBlockStore(BlockStore):
-	_state = Dict[bytes, bytes]
+	_state: Dict[bytes, bytes]
 
 	def __init__(self, state: Optional[Dict[bytes, bytes]]=None) -> None:
 		"""

src/atmst/blockstore/car_file.py

@@ -56,11 +56,19 @@ def __init__(self, file: BinaryIO, validate_hashes: bool=True) -> None:
 		if len(header) != header_len:
 			raise EOFError("not enough CAR header bytes")
 		header_obj = decode_dag_cbor(header)
+		if not isinstance(header_obj, dict):
+			raise TypeError
 		if header_obj.get("version") != 1:
 			raise ValueError(f"unsupported CAR version ({header_obj.get('version')})")
-		if len(header_obj["roots"]) != 1:
-			raise ValueError(f"unsupported number of CAR roots ({len(header_obj['roots'])}, expected 1)")
-		self.car_root = header_obj["roots"][0]
+		roots = header_obj["roots"]
+		if not isinstance(roots, list):
+			raise TypeError
+		if len(roots) != 1:
+			raise ValueError(f"unsupported number of CAR roots ({len(roots)}, expected 1)")
+		root = roots[0]
+		if not isinstance(root, CID):
+			raise TypeError
+		self.car_root = root
 
 		# scan through the CAR to find block offsets
 		self.block_offsets = {}

src/atmst/cartool.py

@@ -20,6 +20,8 @@ def open_car(car_path: str) -> Tuple[ReadOnlyCARBlockStore, dict]:
 	carfile = open(car_path, "rb")
 	bs = ReadOnlyCARBlockStore(carfile)
 	commit = decode_dag_cbor(bs.get_block(bytes(bs.car_root)))
+	if not isinstance(commit, dict):
+		raise TypeError
 	return bs, commit
 
 def print_info(car_path: str) -> None: