Type Traversable/list_traverse() better, make IterablleObj a protocol

1 files changed, 10 insertions, 14 deletions

diff --git a/git/objects/util.py b/git/objects/util.py
index fce62af2..bc6cdf8f 100644
--- a/git/objects/util.py
+++ b/git/objects/util.py
@@ -23,7 +23,7 @@ from datetime import datetime, timedelta, tzinfo
 from typing import (Any, Callable, Deque, Iterator, NamedTuple, overload, Sequence,
                     TYPE_CHECKING, Tuple, Type, TypeVar, Union, cast)
 
-from git.types import Literal
+from git.types import Literal, TypeGuard
 
 if TYPE_CHECKING:
     from io import BytesIO, StringIO
@@ -306,24 +306,20 @@ class Traversable(object):
         """
         raise NotImplementedError("To be implemented in subclass")
 
-    def list_traverse(self, *args: Any, **kwargs: Any
-                      ) -> Union[IterableList['TraversableIterableObj'],
-                                 IterableList[Tuple[Union[None, 'TraversableIterableObj'], 'TraversableIterableObj']]]:
+    def list_traverse(self, *args: Any, **kwargs: Any) -> IterableList['TraversableIterableObj']:
         """
         :return: IterableList with the results of the traversal as produced by
             traverse()
             List objects must be IterableObj and Traversable e.g. Commit, Submodule"""
 
-        out: Union[IterableList['TraversableIterableObj'],
-                   IterableList[Tuple[Union[None, 'TraversableIterableObj'], 'TraversableIterableObj']]]
-
-        # def is_TraversableIterableObj(inp: Union['Traversable', IterableObj]) -> TypeGuard['TraversableIterableObj']:
-        #     return isinstance(self, TraversableIterableObj)
-        # assert is_TraversableIterableObj(self), f"{type(self)}"
-
-        self = cast('TraversableIterableObj', self)
-        out = IterableList(self._id_attribute_)
-        out.extend(self.traverse(*args, **kwargs))  # type: ignore
+        def is_TraversableIterableObj(inp: 'Traversable') -> TypeGuard['TraversableIterableObj']:
+            # return isinstance(self, TraversableIterableObj)
+            # Can it be anythin else?
+            return isinstance(self, Traversable)
+        
+        assert is_TraversableIterableObj(self), f"{type(self)}"
+        out: IterableList['TraversableIterableObj'] = IterableList(self._id_attribute_)
+        out.extend(self.traverse(*args, **kwargs))
         return out
 
     def traverse(self,