@@ -15,12 +15,13 @@
 
 # typing ------------------------------------------------------------------
 
-from typing import Any, Iterator, List, Match, Optional, Tuple, Type, Union, TYPE_CHECKING, cast
+from typing import Any, Iterator, List, Match, Optional, Tuple, Type, TypeVar, Union, TYPE_CHECKING
 from git.types import PathLike, TBD, Literal, TypeGuard
 
 if TYPE_CHECKING:
     from .objects.tree import Tree
     from git.repo.base import Repo
+    from git.objects.base import IndexObject
 
     from subprocess import Popen
 
@@ -175,7 +176,10 @@ def diff(self, other: Union[Type[Index], Type['Tree'], object, None, str] = Inde
         return index
 
 
-class DiffIndex(list):
+T_Diff = TypeVar('T_Diff', bound='Diff')
+
+
+class DiffIndex(List[T_Diff]):
 
     """Implements an Index for diffs, allowing a list of Diffs to be queried by
     the diff properties.
@@ -189,7 +193,7 @@ class DiffIndex(list):
     # T = Changed in the type
     change_type = ("A", "C", "D", "R", "M", "T")
 
-    def iter_change_type(self, change_type: Lit_change_type) -> Iterator['Diff']:
+    def iter_change_type(self, change_type: Lit_change_type) -> Iterator[T_Diff]:
         """
         :return:
             iterator yielding Diff instances that match the given change_type
@@ -207,8 +211,6 @@ def iter_change_type(self, change_type: Lit_change_type) -> Iterator['Diff']:
             raise ValueError("Invalid change type: %s" % change_type)
 
         for diff in self:
-            diff = cast('Diff', diff)
-
             if diff.change_type == change_type:
                 yield diff
             elif change_type == "A" and diff.new_file:
@@ -289,7 +291,7 @@ def __init__(self, repo: 'Repo',
                  a_mode: Union[bytes, str, None], b_mode: Union[bytes, str, None],
                  new_file: bool, deleted_file: bool, copied_file: bool,
                  raw_rename_from: Optional[bytes], raw_rename_to: Optional[bytes],
-                 diff: Union[str, bytes, None], change_type: Optional[str], score: Optional[int]) -> None:
+                 diff: Union[str, bytes, None], change_type: Optional[Lit_change_type], score: Optional[int]) -> None:
 
         assert a_rawpath is None or isinstance(a_rawpath, bytes)
         assert b_rawpath is None or isinstance(b_rawpath, bytes)
@@ -308,19 +310,21 @@ def __init__(self, repo: 'Repo',
                         repo = submodule.module()
                     break
 
+        self.a_blob: Union['IndexObject', None]
         if a_blob_id is None or a_blob_id == self.NULL_HEX_SHA:
             self.a_blob = None
         else:
             self.a_blob = Blob(repo, hex_to_bin(a_blob_id), mode=self.a_mode, path=self.a_path)
 
+        self.b_blob: Union['IndexObject', None]
         if b_blob_id is None or b_blob_id == self.NULL_HEX_SHA:
             self.b_blob = None
         else:
             self.b_blob = Blob(repo, hex_to_bin(b_blob_id), mode=self.b_mode, path=self.b_path)
 
-        self.new_file = new_file
-        self.deleted_file = deleted_file
-        self.copied_file = copied_file
+        self.new_file: bool = new_file
+        self.deleted_file: bool = deleted_file
+        self.copied_file: bool = copied_file
 
         # be clear and use None instead of empty strings
         assert raw_rename_from is None or isinstance(raw_rename_from, bytes)
@@ -329,7 +333,7 @@ def __init__(self, repo: 'Repo',
         self.raw_rename_to = raw_rename_to or None
 
         self.diff = diff
-        self.change_type = change_type
+        self.change_type: Union[Lit_change_type, None] = change_type
         self.score = score
 
     def __eq__(self, other: object) -> bool:
@@ -449,7 +453,7 @@ def _index_from_patch_format(cls, repo: 'Repo', proc: TBD) -> DiffIndex:
 
         # for now, we have to bake the stream
         text = b''.join(text_list)
-        index = DiffIndex()
+        index: 'DiffIndex' = DiffIndex()
         previous_header = None
         header = None
         a_path, b_path = None, None  # for mypy
@@ -560,7 +564,7 @@ def _index_from_raw_format(cls, repo: 'Repo', proc: 'Popen') -> 'DiffIndex':
         # handles
         # :100644 100644 687099101... 37c5e30c8... M    .gitignore
 
-        index = DiffIndex()
+        index: 'DiffIndex' = DiffIndex()
         handle_process_output(proc, lambda byt: cls._handle_diff_line(byt, repo, index),
                               None, finalize_process, decode_streams=False)
 
 
@@ -52,7 +52,7 @@ def __del__(self) -> None:
 
 #{ Decorators
 
-def post_clear_cache(func: Callable[..., Any]) -> Callable[..., Any]:
+def post_clear_cache(func: Callable[..., _T]) -> Callable[..., _T]:
     """Decorator for functions that alter the index using the git command. This would
     invalidate our possibly existing entries dictionary which is why it must be
     deleted to allow it to be lazily reread later.
@@ -63,7 +63,7 @@ def post_clear_cache(func: Callable[..., Any]) -> Callable[..., Any]:
     """
 
     @wraps(func)
-    def post_clear_cache_if_not_raised(self, *args: Any, **kwargs: Any) -> Any:
+    def post_clear_cache_if_not_raised(self, *args: Any, **kwargs: Any) -> _T:
         rval = func(self, *args, **kwargs)
         self._delete_entries_cache()
         return rval
@@ -72,13 +72,13 @@ def post_clear_cache_if_not_raised(self, *args: Any, **kwargs: Any) -> Any:
     return post_clear_cache_if_not_raised
 
 
-def default_index(func: Callable[..., Any]) -> Callable[..., Any]:
+def default_index(func: Callable[..., _T]) -> Callable[..., _T]:
     """Decorator assuring the wrapped method may only run if we are the default
     repository index. This is as we rely on git commands that operate
     on that index only. """
 
     @wraps(func)
-    def check_default_index(self, *args: Any, **kwargs: Any) -> Any:
+    def check_default_index(self, *args: Any, **kwargs: Any) -> _T:
         if self._file_path != self._index_path():
             raise AssertionError(
                 "Cannot call %r on indices that do not represent the default git index" % func.__name__)