fix: support index protocol in IterableList lookups

`IterableList.__getitem__` advertises `SupportsIndex`, but routes every non-`int` index through named lookup. Valid objects implementing `__index__` therefore raise a string-concatenation `TypeError` instead of selecting an element.

Delegate non-string, non-slice indices to the built-in list implementation, which already handles the index protocol and bounds checks. Keep named lookup and explicit slice rejection unchanged.

Six protocol/bounds regressions fail before this fix; a lookup/slice control passes. Utility and typing modules pass with both CLI and Gix backends (128 passed, 39 skipped each). Applicable pre-commit checks pass.

Assisted-by: OpenAI Codex (model: unknown, autonomous)

Author: gavenren

git/util.py

@@ -1333,10 +1333,10 @@ def __getattr__(self, attr: str) -> T_IterableObj:
     def __getitem__(  # type: ignore[override]  # pyright: ignore[reportIncompatibleMethodOverride]
         self, index: Union[SupportsIndex, int, slice, str]
     ) -> T_IterableObj:
-        if isinstance(index, int):
-            return list.__getitem__(self, index)
-        elif isinstance(index, slice):
+        if isinstance(index, slice):
             raise ValueError("Index should be an int or str")
+        elif not isinstance(index, str):
+            return list.__getitem__(self, index)
         else:
             try:
                 return self.__getattr__(cast(str, index))

test/test_util.py

@@ -280,6 +280,45 @@ def __repr__(self):
         return f"{type(self).__name__}({self.name!r})"
 
 
+@pytest.mark.parametrize("prefix", ["", "refs/"])
+@pytest.mark.parametrize("position", [0, -1])
+def test_iterable_list_accepts_index_protocol(prefix, position):
+    class Index:
+        def __index__(self):
+            return position
+
+    values = IterableList("name", prefix)
+    members = [_Member(prefix + name) for name in ("one", "two")]
+    values.extend(members)
+    assert values[Index()] is members[position]
+
+
+@pytest.mark.parametrize("position", [2, -3])
+def test_iterable_list_index_protocol_preserves_bounds_errors(position):
+    class Index:
+        def __index__(self):
+            return position
+
+    values = IterableList("name")
+    values.extend([_Member("one"), _Member("two")])
+    with pytest.raises(IndexError):
+        values[Index()]
+
+
+def test_iterable_list_index_protocol_preserves_named_lookup_and_slice_rejection():
+    values = IterableList("name", "refs/")
+    named = _Member("refs/0")
+    values.extend([named, _Member("refs/one")])
+    assert values["0"] is named
+    assert values[False] is named
+    with pytest.raises(IndexError):
+        values["missing"]
+    with pytest.raises(ValueError):
+        values[:1]
+    with pytest.raises(TypeError):
+        values[0.0]
+
+
 @ddt.ddt
 class TestUtils(TestBase):
     """Tests for most utilities in :mod:`git.util`."""