Complete type annotations in pip/_internal/index and pip/_internal/models

src/pip/_internal/index/package_finder.py

@@ -502,7 +502,7 @@ def _sort_key(self, candidate: InstallationCandidate) -> CandidateSortingKey:
         """
         valid_tags = self._supported_tags
         support_num = len(valid_tags)
-        build_tag = ()  # type: BuildTag
+        build_tag: BuildTag = ()
         binary_preference = 0
         link = candidate.link
         if link.is_wheel:
@@ -603,7 +603,7 @@ def __init__(
         self.format_control = format_control
 
         # These are boring links that have already been logged somehow.
-        self._logged_links = set()  # type: Set[Link]
+        self._logged_links: Set[Link] = set()
 
     # Don't include an allow_yanked default value to make sure each call
     # site considers whether yanked releases are allowed. This also causes
@@ -699,7 +699,7 @@ def _sort_links(self, links: Iterable[Link]) -> List[Link]:
         second, while eliminating duplicates
         """
         eggs, no_eggs = [], []
-        seen = set()  # type: Set[Link]
+        seen: Set[Link] = set()
         for link in links:
             if link not in seen:
                 seen.add(link)
@@ -871,7 +871,7 @@ def find_requirement(
         )
         best_candidate = best_candidate_result.best_candidate
 
-        installed_version = None    # type: Optional[_BaseVersion]
+        installed_version: Optional[_BaseVersion] = None
         if req.satisfied_by is not None:
             installed_version = parse_version(req.satisfied_by.version)
 

src/pip/_internal/models/search_scope.py

@@ -36,7 +36,7 @@ def create(
         # it and if it exists, use the normalized version.
         # This is deliberately conservative - it might be fine just to
         # blindly normalize anything starting with a ~...
-        built_find_links = []  # type: List[str]
+        built_find_links: List[str] = []
         for link in find_links:
             if link.startswith('~'):
                 new_link = normalize_path(link)

src/pip/_internal/models/selection_prefs.py

@@ -23,8 +23,7 @@ def __init__(
         format_control: Optional[FormatControl] = None,
         prefer_binary: bool = False,
         ignore_requires_python: Optional[bool] = None,
-    ):
-        # type: (...) -> None
+    ) -> None:
         """Create a SelectionPreferences object.
 
         :param allow_yanked: Whether files marked as yanked (in the sense

src/pip/_internal/models/target_python.py

@@ -62,7 +62,7 @@ def __init__(
         self.py_version_info = py_version_info
 
         # This is used to cache the return value of get_tags().
-        self._valid_tags = None  # type: Optional[List[Tag]]
+        self._valid_tags: Optional[List[Tag]] = None
 
     def format_given(self) -> str:
         """