--- a/mercurial/mail.py	Wed Dec 20 20:13:22 2023 +0100
+++ b/mercurial/mail.py	Tue Dec 19 21:29:34 2023 +0100
@@ -21,6 +21,7 @@
 from typing import (
     Any,
     List,
+    Optional,
     Tuple,
     Union,
 )
@@ -113,8 +114,7 @@
         return new_socket
 
 
-def _pyhastls():
-    # type: () -> bool
+def _pyhastls() -> bool:
     """Returns true iff Python has TLS support, false otherwise."""
     try:
         import ssl
@@ -277,8 +277,7 @@
             )
 
 
-def codec2iana(cs):
-    # type: (str) -> str
+def codec2iana(cs: str) -> str:
     ''' '''
     cs = email.charset.Charset(cs).input_charset.lower()
 
@@ -288,8 +287,11 @@
     return cs
 
 
-def mimetextpatch(s, subtype='plain', display=False):
-    # type: (bytes, str, bool) -> email.message.Message
+def mimetextpatch(
+    s: bytes,
+    subtype: str = 'plain',
+    display: bool = False,
+) -> email.message.Message:
     """Return MIME message suitable for a patch.
     Charset will be detected by first trying to decode as us-ascii, then utf-8,
     and finally the global encodings. If all those fail, fall back to
@@ -314,8 +316,9 @@
     return mimetextqp(s, subtype, "iso-8859-1")
 
 
-def mimetextqp(body, subtype, charset):
-    # type: (bytes, str, str) -> email.message.Message
+def mimetextqp(
+    body: bytes, subtype: str, charset: str
+) -> email.message.Message:
     """Return MIME message.
     Quoted-printable transfer encoding will be used if necessary.
     """
@@ -340,8 +343,7 @@
     return msg
 
 
-def _charsets(ui):
-    # type: (Any) -> List[str]
+def _charsets(ui: Any) -> List[str]:
     '''Obtains charsets to send mail parts not containing patches.'''
     charsets = [
         pycompat.sysstr(cs.lower())
@@ -358,8 +360,7 @@
     return [cs for cs in charsets if not cs.endswith('ascii')]
 
 
-def _encode(ui, s, charsets):
-    # type: (Any, bytes, List[str]) -> Tuple[bytes, str]
+def _encode(ui: Any, s: bytes, charsets: List[str]) -> Tuple[bytes, str]:
     """Returns (converted) string, charset tuple.
     Finds out best charset by cycling through sendcharsets in descending
     order. Tries both encoding and fallbackencoding for input. Only as
@@ -409,8 +410,12 @@
     return s, 'us-ascii'
 
 
-def headencode(ui, s, charsets=None, display=False):
-    # type: (Any, Union[bytes, str], List[str], bool) -> str
+def headencode(
+    ui: Any,
+    s: Union[bytes, str],
+    charsets: Optional[List[str]] = None,
+    display: bool = False,
+) -> str:
     '''Returns RFC-2047 compliant header from given string.'''
     if not display:
         # split into words?
@@ -419,8 +424,9 @@
     return encoding.strfromlocal(s)
 
 
-def _addressencode(ui, name, addr, charsets=None):
-    # type: (Any, str, str, List[str]) -> str
+def _addressencode(
+    ui: Any, name: str, addr: str, charsets: Optional[List[str]] = None
+) -> str:
     addr = encoding.strtolocal(addr)
     name = headencode(ui, name, charsets)
     try:
@@ -439,8 +445,12 @@
     return email.utils.formataddr((name, encoding.strfromlocal(addr)))
 
 
-def addressencode(ui, address, charsets=None, display=False):
-    # type: (Any, bytes, List[str], bool) -> str
+def addressencode(
+    ui: Any,
+    address: bytes,
+    charsets: Optional[List[str]] = None,
+    display: bool = False,
+) -> str:
     '''Turns address into RFC-2047 compliant header.'''
     if display or not address:
         return encoding.strfromlocal(address or b'')
@@ -448,8 +458,12 @@
     return _addressencode(ui, name, addr, charsets)
 
 
-def addrlistencode(ui, addrs, charsets=None, display=False):
-    # type: (Any, List[bytes], List[str], bool) -> List[str]
+def addrlistencode(
+    ui: Any,
+    addrs: List[bytes],
+    charsets: Optional[List[str]] = None,
+    display: bool = False,
+) -> List[str]:
     """Turns a list of addresses into a list of RFC-2047 compliant headers.
     A single element of input list may contain multiple addresses, but output
     always has one address per item"""
@@ -468,8 +482,12 @@
     return result
 
 
-def mimeencode(ui, s, charsets=None, display=False):
-    # type: (Any, bytes, List[str], bool) -> email.message.Message
+def mimeencode(
+    ui: Any,
+    s: bytes,
+    charsets: Optional[List[str]] = None,
+    display: bool = False,
+) -> email.message.Message:
     """creates mime text object, encodes it if needed, and sets
     charset and transfer-encoding accordingly."""
     cs = 'us-ascii'
@@ -481,8 +499,7 @@
 Generator = email.generator.BytesGenerator
 
 
-def parse(fp):
-    # type: (Any) -> email.message.Message
+def parse(fp: Any) -> email.message.Message:
     ep = email.parser.Parser()
     # disable the "universal newlines" mode, which isn't binary safe.
     # I have no idea if ascii/surrogateescape is correct, but that's
@@ -496,14 +513,12 @@
         fp.detach()
 
 
-def parsebytes(data):
-    # type: (bytes) -> email.message.Message
+def parsebytes(data: bytes) -> email.message.Message:
     ep = email.parser.BytesParser()
     return ep.parsebytes(data)
 
 
-def headdecode(s):
-    # type: (Union[email.header.Header, bytes]) -> bytes
+def headdecode(s: Union[email.header.Header, bytes]) -> bytes:
     '''Decodes RFC-2047 header'''
     uparts = []
     for part, charset in email.header.decode_header(s):