Fixes for CI

newsfragments/3175.doc.rst

@@ -0,0 +1 @@
+Warn if a user forgot to implement ``.derive`` for an ExceptionGroup subclass.

src/trio/_core/_run.py

@@ -52,7 +52,7 @@
 )
 
 if sys.version_info < (3, 11):
-    from exceptiongroup import BaseExceptionGroup
+    from exceptiongroup import BaseExceptionGroup, ExceptionGroup
 
 
 if TYPE_CHECKING:

src/trio/_core/_tests/test_run.py

@@ -10,7 +10,7 @@
 import weakref
 from contextlib import ExitStack, contextmanager, suppress
 from math import inf, nan
-from typing import TYPE_CHECKING, NoReturn, Self, TypeVar
+from typing import TYPE_CHECKING, NoReturn, TypeVar
 from unittest import mock
 
 import outcome
@@ -47,6 +47,8 @@
         Sequence,
     )
 
+    from typing_extensions import Self
+
 if sys.version_info < (3, 11):
     from exceptiongroup import BaseExceptionGroup, ExceptionGroup
 
@@ -2859,7 +2861,7 @@ def run(self, fn: Callable[[], object]) -> object:
 
 
 def test_run_with_custom_exception_group() -> None:
-    class ExceptionGroupForTest(ExceptionGroup):
+    class ExceptionGroupForTest(ExceptionGroup[Exception]):
         @staticmethod
         def for_test(message: str, excs: list[Exception]) -> ExceptionGroupForTest:
             raise NotImplementedError()
@@ -2897,7 +2899,7 @@ def for_test(message: str, excs: list[Exception]) -> AbnormalNew:
             return AbnormalNew(excs)
 
     for check in (check1, check2, check3):
-        for error in (HasDerive, NormalNew, AbnormalNew):
+        for error in [HasDerive, NormalNew, AbnormalNew]:
             if check is check3:
                 if error in (NormalNew, AbnormalNew):
                     with (