Nodes in trie lib use Bytes as a type for Nibble

[ClementWalter]

Metadata

• Hardfork: cancun

What was wrong?

https://github.com/ethereum/execution-specs/blob/master/src/ethereum/cancun/trie.py#L80-L95

@slotted_freezable
@dataclass
class LeafNode:
    """Leaf node in the Merkle Trie"""

    rest_of_key: Bytes
    value: rlp.Extended


@slotted_freezable
@dataclass
class ExtensionNode:
    """Extension node in the Merkle Trie"""

    key_segment: Bytes
    subnode: rlp.Extended

rest_of_key and key_segment should be Nibble (type to create) instead of Bytes, as it's not true that any bytes. can be in (see for example encode_internal_node where it crashes in nibble_list_to_compact(node.rest_of_key, True)

[SamWilsn]

Is this similar to #241?

[ClementWalter]

similar indeed, the idea is that one should be able to check nibble at "compile" time. But I'd go with what you have already with FixedUint and use a Nibble or Nibbles = List[Uint4]

[ClementWalter]

same issue with patricialize defined as

def patricialize(
    obj: Mapping[Bytes, Bytes], level: Uint
) -> Optional[InternalNode]:

where keys should be nibble, as also stated in the docstring

    obj :
        Underlying trie key-value pairs, with keys in nibble-list format.