Upgrade to latest mypy

.pre-commit-config.yaml

@@ -8,7 +8,7 @@ repos:
       - id: trailing-whitespace
 
   - repo: https://github.com/pre-commit/mirrors-mypy
-    rev: v0.991
+    rev: v1.13.0
     hooks:
       - id: mypy
         exclude: '^(docs|tasks|tests)|setup\.py'

src/packaging/metadata.py

@@ -9,6 +9,7 @@
 import pathlib
 import typing
 from typing import (
+    TYPE_CHECKING,
     Any,
     Callable,
     Generic,
@@ -26,7 +27,7 @@
 
 if "ExceptionGroup" in builtins.__dict__:  # pragma: no cover
     ExceptionGroup = ExceptionGroup
-else:  # pragma: no cover
+elif not TYPE_CHECKING:  # pragma: no cover
 
     class ExceptionGroup(Exception):
         """A minimal implementation of :external:exc:`ExceptionGroup` from Python 3.11.
@@ -222,12 +223,14 @@ def _get_payload(msg: email.message.Message, source: bytes | str) -> str:
     # If our source is a str, then our caller has managed encodings for us,
     # and we don't need to deal with it.
     if isinstance(source, str):
-        payload: str = msg.get_payload()
+        payload = msg.get_payload()
+        assert isinstance(payload, str)
         return payload
     # If our source is a bytes, then we're managing the encoding and we need
     # to deal with it.
     else:
-        bpayload: bytes = msg.get_payload(decode=True)
+        bpayload = msg.get_payload(decode=True)
+        assert isinstance(bpayload, bytes)
         try:
             return bpayload.decode("utf8", "strict")
         except UnicodeDecodeError as exc:
@@ -434,7 +437,7 @@ def parse_email(data: bytes | str) -> tuple[RawMetadata, dict[str, list[str]]]:
         payload = _get_payload(parsed, data)
     except ValueError:
         unparsed.setdefault("description", []).append(
-            parsed.get_payload(decode=isinstance(data, bytes))
+            parsed.get_payload(decode=isinstance(data, bytes))  # type: ignore[call-overload]
         )
     else:
         if payload:

src/packaging/tags.py

@@ -490,7 +490,7 @@ def ios_platforms(
         # if iOS is the current platform, ios_ver *must* be defined. However,
         # it won't exist for CPython versions before 3.13, which causes a mypy
         # error.
-        _, release, _, _ = platform.ios_ver()  # type: ignore[attr-defined]
+        _, release, _, _ = platform.ios_ver()
         version = cast("AppleVersion", tuple(map(int, release.split(".")[:2])))
 
     if multiarch is None:

src/packaging/version.py

@@ -493,7 +493,9 @@ def _parse_letter_version(
             letter = "post"
 
         return letter, int(number)
-    if not letter and number:
+
+    assert not letter
+    if number:
         # We assume if we are given a number, but we are not given a letter
         # then this is using the implicit post release syntax (e.g. 1.0-1)
         letter = "post"