invoices: minor clean-up (type hints, mark broken things)

also rm some dead code

electrum/paymentrequest.py

@@ -25,7 +25,7 @@
 import hashlib
 import sys
 import time
-from typing import Optional, List
+from typing import Optional, List, TYPE_CHECKING
 import asyncio
 import urllib.parse
 
@@ -41,13 +41,16 @@ except ImportError:
 
 from . import bitcoin, ecc, util, transaction, x509, rsakey
 from .util import bh2u, bfh, make_aiohttp_session
-from .invoices import PR_UNPAID, PR_EXPIRED, PR_PAID, PR_UNKNOWN, PR_INFLIGHT
+from .invoices import OnchainInvoice
 from .crypto import sha256
 from .bitcoin import address_to_script
 from .transaction import PartialTxOutput
 from .network import Network
 from .logging import get_logger, Logger
 
+if TYPE_CHECKING:
+    from .simple_config import SimpleConfig
+
 
 _logger = get_logger(__name__)
 
@@ -315,8 +318,7 @@ class PaymentRequest:
             return False, error
 
 
-def make_unsigned_request(req):
-    from .transaction import Transaction
+def make_unsigned_request(req: 'OnchainInvoice'):
     addr = req.get_address()
     time = req.time
     exp = req.exp
@@ -444,7 +446,7 @@ def sign_request_with_x509(pr, key_path, cert_path):
     pr.signature = bytes(sig)
 
 
-def serialize_request(req):
+def serialize_request(req):  # FIXME this is broken
     pr = make_unsigned_request(req)
     signature = req.get('sig')
     requestor = req.get('name')
@@ -455,7 +457,7 @@ def serialize_request(req):
     return pr
 
 
-def make_request(config, req):
+def make_request(config: 'SimpleConfig', req: 'OnchainInvoice'):
     pr = make_unsigned_request(req)
     key_path = config.get('ssl_keyfile')
     cert_path = config.get('ssl_certfile')