BIP352: complete return type annotations in bitcoin_utils

[omipheo]

Summary

The serialization helpers in bip-0352/bitcoin_utils.py are partially
typed. ser_uint32, hash160, and the is_p2* helpers already declare
both argument and return types, but the surrounding from_hex,
ser_uint256, deser_uint256, deser_txid, deser_compact_size,
deser_string, and deser_string_vector helpers omit them.

Fill in the missing return types (and the obvious argument types) so
the file is consistent and so static analysis can flow types through
the callers in reference.py. Follow-up to 2f7117c
("BIP352: fix Any typing").

No behavior changes.

Diff

Function	Before	After
from_hex	def from_hex(hex_string)	def from_hex(hex_string: str) -> BytesIO
ser_uint256	def ser_uint256(u)	def ser_uint256(u: int) -> bytes
deser_uint256	def deser_uint256(f)	def deser_uint256(f: BytesIO) -> int
deser_txid	def deser_txid(txid: str)	def deser_txid(txid: str) -> bytes
deser_compact_size	def deser_compact_size(f: BytesIO)	def deser_compact_size(f: BytesIO) -> int
deser_string	def deser_string(f: BytesIO)	def deser_string(f: BytesIO) -> bytes
deser_string_vector	def deser_string_vector(f: BytesIO)	def deser_string_vector(f: BytesIO) -> List[bytes]

List is added to the existing typing import. The ser_uint32 and
hash160 annotations on adjacent lines were the model.

Verification

Imported the module and round-tripped each helper to confirm runtime
behavior is unchanged:

$ python3 -c "
import sys
sys.path.insert(0, 'bip-0352')
sys.path.insert(0, 'bip-0352/secp256k1lab/src')
import bitcoin_utils
print('from_hex   ', bitcoin_utils.from_hex('deadbeef').read(2).hex())
print('ser_uint32 ', bitcoin_utils.ser_uint32(1).hex())
print('ser_uint256', bitcoin_utils.ser_uint256(1).hex()[:16])
print('deser_txid ', bitcoin_utils.deser_txid('00112233' * 8).hex()[:16])
"
from_hex    dead
ser_uint32  00000001
ser_uint256 0100000000000000
deser_txid  3322110033221100

Type-checker is happy across the whole file (matching @theStack's
verification on the PR):

$ mypy --ignore-missing-imports ./bip-0352/bitcoin_utils.py
Success: no issues found in 1 source file

[jonatack]

Approach ACK

[edilmedeiros]

utACK 3b76c84

[theStack]

ACK 3b76c84

LGTM, and mypy seems to be happy as well:

$ mypy --ignore-missing-imports ./bip-0352/bitcoin_utils.py 
Success: no issues found in 1 source file

non-blocking nit: seems the "Verification" section in the PR description is incomplete?

[jonatack]

seems the "Verification" section in the PR description is incomplete?

@omipheo mind fixing the PR description? (thanks!)

[omipheo]

Done — Verification section in the PR description now has the actual round-trip script + output, and a mypy block mirroring @theStack's check. Thanks for both reviews!