fix: resolve pyright strict-mode errors in test_exception_utils

Add _get_exceptions() helper to provide typed access to
BaseExceptionGroup.exceptions, avoiding reportUnknownMemberType errors.
Use pyright: ignore[reportUnknownArgumentType] for the narrowed
BaseExceptionGroup[Unknown] type after isinstance checks.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: g97iulio1609

tests/shared/test_exception_utils.py

@@ -4,6 +4,7 @@
 
 import asyncio
 import sys
+from collections.abc import Sequence
 
 import anyio
 import pytest
@@ -14,6 +15,11 @@
     from exceptiongroup import BaseExceptionGroup
 
 
+def _get_exceptions(eg: BaseExceptionGroup[BaseException]) -> Sequence[BaseException]:
+    """Return the exceptions tuple with a known type for pyright."""
+    return eg.exceptions
+
+
 # ---------------------------------------------------------------------------
 # collapse_exception_group() unit tests
 # ---------------------------------------------------------------------------
@@ -51,9 +57,10 @@ def test_multiple_real_errors(self) -> None:
         result = collapse_exception_group(eg)
         assert isinstance(result, BaseExceptionGroup)
         # Should contain only the two real errors
-        assert len(result.exceptions) == 2
-        assert e1 in result.exceptions
-        assert e2 in result.exceptions
+        excs = _get_exceptions(result)  # pyright: ignore[reportUnknownArgumentType]
+        assert len(excs) == 2
+        assert e1 in excs
+        assert e2 in excs
 
     def test_single_real_error_no_cancelled(self) -> None:
         """One real error, no Cancelled → unwrap to the real error."""
@@ -69,9 +76,10 @@ def test_multiple_real_errors_no_cancelled(self) -> None:
         eg = BaseExceptionGroup("task group", [e1, e2])
         result = collapse_exception_group(eg)
         assert isinstance(result, BaseExceptionGroup)
-        assert len(result.exceptions) == 2
-        assert e1 in result.exceptions
-        assert e2 in result.exceptions
+        excs = _get_exceptions(result)  # pyright: ignore[reportUnknownArgumentType]
+        assert len(excs) == 2
+        assert e1 in excs
+        assert e2 in excs
 
 
 # ---------------------------------------------------------------------------
@@ -108,7 +116,8 @@ async def test_multiple_failures_preserved(self) -> None:
 
         # The group should contain both real errors
         eg = exc_info.value
-        types = {type(e) for e in eg.exceptions}
+        excs = _get_exceptions(eg)  # pyright: ignore[reportUnknownArgumentType]
+        types = {type(e) for e in excs}
         assert ValueError in types
         assert RuntimeError in types