From e520bd88077014e69d4b54a9303498b18974adca Mon Sep 17 00:00:00 2001
From: CoolCat467 <52022020+CoolCat467@users.noreply.github.com>
Date: Sun, 6 Aug 2023 01:22:47 -0500
Subject: [PATCH 01/13] WIP: Add typing for `_core/_multierror.py`

---
 trio/_core/_multierror.py | 168 ++++++++++++++++++++++++++++++++++----
 1 file changed, 150 insertions(+), 18 deletions(-)

diff --git a/trio/_core/_multierror.py b/trio/_core/_multierror.py
index 3c6ebb789f..1791883aee 100644
--- a/trio/_core/_multierror.py
+++ b/trio/_core/_multierror.py
@@ -2,7 +2,8 @@
 
 import sys
 import warnings
-from typing import TYPE_CHECKING
+from collections.abc import Callable, Iterable
+from typing import TYPE_CHECKING, TypeVar
 
 import attr
 
@@ -15,12 +16,16 @@
 
 if TYPE_CHECKING:
     from types import TracebackType
+
+    from typing_extensions import Self
 ################################################################
 # MultiError
 ################################################################
 
 
-def _filter_impl(handler, root_exc):
+def _filter_impl(
+    handler: Callable[[BaseException], BaseException], root_exc: BaseException
+) -> BaseException | None:
     # We have a tree of MultiError's, like:
     #
     #  MultiError([
@@ -79,7 +84,9 @@ def _filter_impl(handler, root_exc):
 
     # Filters a subtree, ignoring tracebacks, while keeping a record of
     # which MultiErrors were preserved unchanged
-    def filter_tree(exc, preserved):
+    def filter_tree(
+        exc: MultiError | BaseException, preserved: set[int]
+    ) -> MultiError | BaseException | None:
         if isinstance(exc, MultiError):
             new_exceptions = []
             changed = False
@@ -103,7 +110,9 @@ def filter_tree(exc, preserved):
                 new_exc.__context__ = exc
             return new_exc
 
-    def push_tb_down(tb, exc, preserved):
+    def push_tb_down(
+        tb: TracebackType | None, exc: BaseException, preserved: set[int]
+    ) -> None:
         if id(exc) in preserved:
             return
         new_tb = concat_tb(tb, exc.__traceback__)
@@ -114,7 +123,7 @@ def push_tb_down(tb, exc, preserved):
         else:
             exc.__traceback__ = new_tb
 
-    preserved = set()
+    preserved: set[int] = set()
     new_root_exc = filter_tree(root_exc, preserved)
     push_tb_down(None, root_exc, preserved)
     # Delete the local functions to avoid a reference cycle (see
@@ -130,9 +139,9 @@ def push_tb_down(tb, exc, preserved):
 # frame show up in the traceback; otherwise, we leave no trace.)
 @attr.s(frozen=True)
 class MultiErrorCatcher:
-    _handler = attr.ib()
+    _handler: Callable[[BaseException], BaseException] = attr.ib()
 
-    def __enter__(self):
+    def __enter__(self) -> None:
         pass
 
     def __exit__(
@@ -167,6 +176,51 @@ def __exit__(
         return False
 
 
+# types: type-arg error: Missing type parameters for generic type "BaseExceptionGroup"
+# types: note: Another file has errors: trio/_timeouts.py
+# types: note: Another file has errors: trio/_core/_entry_queue.py
+# types: note: Another file has errors: trio/_signals.py
+# types: note: Another file has errors: trio/_util.py
+# types: note: Another file has errors: trio/_subprocess_platform/waitid.py
+# types: note: Another file has errors: trio/testing/__init__.py
+# types: note: Another file has errors: trio/_core/_thread_cache.py
+# types: note: Another file has errors: trio/_channel.py
+# types: note: Another file has errors: trio/testing/_network.py
+# types: note: Another file has errors: trio/_core/_wakeup_socketpair.py
+# types: note: Another file has errors: trio/_subprocess.py
+# types: note: Another file has errors: trio/_core/_unbounded_queue.py
+# types: note: Another file has errors: trio/_path.py
+# types: note: Another file has errors: trio/testing/_memory_streams.py
+# types: note: Another file has errors: trio/_highlevel_open_unix_stream.py
+# types: note: Another file has errors: trio/testing/_checkpoints.py
+# types: note: Another file has errors: trio/_core/_traps.py
+# types: note: Another file has errors: trio/_highlevel_serve_listeners.py
+# types: note: Another file has errors: trio/_core/_generated_instrumentation.py
+# types: note: Another file has errors: trio/_socket.py
+# types: note: Another file has errors: trio/_core/_io_common.py
+# types: note: Another file has errors: trio/lowlevel.py
+# types: note: Another file has errors: trio/_core/_ki.py
+# types: note: Another file has errors: trio/_core/_asyncgens.py
+# types: note: Another file has errors: trio/_highlevel_ssl_helpers.py
+# types: note: Another file has errors: trio/_ssl.py
+# types: note: Another file has errors: trio/testing/_trio_test.py
+# types: note: Another file has errors: trio/_core/_parking_lot.py
+# types: note: Another file has errors: trio/_highlevel_open_tcp_listeners.py
+# types: note: Another file has errors: trio/testing/_check_streams.py
+# types: note: Another file has errors: trio/_highlevel_open_tcp_stream.py
+# types: note: Another file has errors: trio/_core/_generated_io_epoll.py
+# types: note: Another file has errors: trio/_core/_mock_clock.py
+# types: note: Another file has errors: trio/_sync.py
+# types: note: Another file has errors: trio/_threads.py
+# types: note: Another file has errors: trio/_dtls.py
+# types: note: Another file has errors: trio/_core/_run.py
+# types: note: Another file has errors: trio/__init__.py
+# types: note: Another file has errors: trio/_core/_generated_run.py
+# types: note: Another file has errors: trio/_highlevel_socket.py
+# types: note: Another file has errors: trio/_unix_pipes.py
+# types: note: Another file has errors: trio/_core/_io_epoll.py
+# types: note: Another file has errors: trio/testing/_sequencer.py
+# types: type-arg error: Missing type parameters for generic type "BaseExceptionGroup"
 class MultiError(BaseExceptionGroup):
     """An exception that contains other exceptions; also known as an
     "inception".
@@ -190,7 +244,9 @@ class MultiError(BaseExceptionGroup):
 
     """
 
-    def __init__(self, exceptions, *, _collapse=True):
+    def __init__(
+        self, exceptions: list[BaseException], *, _collapse: bool = True
+    ) -> None:
         self.collapse = _collapse
 
         # Avoid double initialization when _collapse is True and exceptions[0] returned
@@ -201,7 +257,9 @@ def __init__(self, exceptions, *, _collapse=True):
 
         super().__init__("multiple tasks failed", exceptions)
 
-    def __new__(cls, exceptions, *, _collapse=True):
+    def __new__(
+        cls, exceptions: Iterable[BaseException], *, _collapse: bool = True
+    ) -> MultiError | Self:
         exceptions = list(exceptions)
         for exc in exceptions:
             if not isinstance(exc, BaseException):
@@ -210,7 +268,9 @@ def __new__(cls, exceptions, *, _collapse=True):
             # If this lone object happens to itself be a MultiError, then
             # Python will implicitly call our __init__ on it again.  See
             # special handling in __init__.
-            return exceptions[0]
+            single = exceptions[0]
+            assert isinstance(single, MultiError)
+            return single
         else:
             # The base class __new__() implicitly invokes our __init__, which
             # is what we want.
@@ -223,6 +283,58 @@ def __new__(cls, exceptions, *, _collapse=True):
 
             return super().__new__(cls, "multiple tasks failed", exceptions)
 
+    # types: Error running mypy: Daemon crashed!
+    # types: Traceback (most recent call last):
+    # types:   File "mypy/suggestions.py", line 296, in restore_after
+    # types:   File "mypy/suggestions.py", line 267, in suggest
+    # types:   File "mypy/suggestions.py", line 502, in get_suggestion
+    # types:   File "mypy/suggestions.py", line 444, in find_best
+    # types:   File "mypy/suggestions.py", line 675, in try_type
+    # types:   File "mypy/server/update.py", line 314, in trigger
+    # types:   File "mypy/server/update.py", line 881, in propagate_changes_using_dependencies
+    # types:   File "mypy/server/update.py", line 1010, in reprocess_nodes
+    # types:   File "mypy/semanal_main.py", line 144, in semantic_analysis_for_targets
+    # types:   File "mypy/semanal_main.py", line 291, in process_top_level_function
+    # types:   File "mypy/semanal_main.py", line 349, in semantic_analyze_target
+    # types:   File "mypy/semanal.py", line 603, in refresh_partial
+    # types:   File "mypy/semanal.py", line 6453, in accept
+    # types:   File "mypy/errors.py", line 1177, in report_internal_error
+    # types:   File "mypy/semanal.py", line 6451, in accept
+    # types:   File "mypy/nodes.py", line 786, in accept
+    # types:   File "mypy/semanal.py", line 833, in visit_func_def
+    # types:   File "mypy/semanal.py", line 865, in analyze_func_def
+    # types:   File "mypy/typeanal.py", line 950, in visit_callable_type
+    # types:   File "mypy/typeanal.py", line 1522, in anal_type
+    # types:   File "mypy/types.py", line 2294, in accept
+    # types:   File "mypy/typeanal.py", line 1051, in visit_tuple_type
+    # types:   File "mypy/typeanal.py", line 1512, in anal_array
+    # types:   File "mypy/typeanal.py", line 1522, in anal_type
+    # types:   File "mypy/types.py", line 1917, in accept
+    # types:   File "mypy/typeanal.py", line 931, in visit_callable_type
+    # types:   File "mypy/typeanal.py", line 1469, in bind_function_type_variables
+    # types: AssertionError
+    # types: During handling of the above exception, another exception occurred:
+    # types: Traceback (most recent call last):
+    # types:   File "mypy/dmypy_server.py", line 234, in serve
+    # types:   File "mypy/dmypy_server.py", line 281, in run_command
+    # types:   File "mypy/dmypy_server.py", line 931, in cmd_suggest
+    # types:   File "mypy/suggestions.py", line 265, in suggest
+    # types:   File "/usr/lib/python3.11/contextlib.py", line 155, in __exit__
+    # types:     self.gen.throw(typ, value, traceback)
+    # types:   File "mypy/suggestions.py", line 298, in restore_after
+    # types:   File "mypy/suggestions.py", line 687, in reload
+    # types:   File "mypy/server/update.py", line 267, in update
+    # types:   File "mypy/server/update.py", line 369, in update_one
+    # types:   File "mypy/server/update.py", line 426, in update_module
+    # types:   File "mypy/server/astdiff.py", line 223, in snapshot_symbol_table
+    # types:   File "mypy/server/astdiff.py", line 236, in snapshot_definition
+    # types:   File "mypy/server/astdiff.py", line 315, in snapshot_type
+    # types:   File "mypy/types.py", line 1917, in accept
+    # types:   File "mypy/server/astdiff.py", line 439, in visit_callable_type
+    # types:   File "mypy/types.py", line 1900, in is_type_obj
+    # types:   File "mypy/nodes.py", line 3170, in is_metaclass
+    # types:   File "mypy/nodes.py", line 3180, in has_base
+    # types: AttributeError: attribute 'mro' of 'TypeInfo' undefined
     def __reduce__(self):
         return (
             self.__new__,
@@ -230,12 +342,13 @@ def __reduce__(self):
             {"collapse": self.collapse},
         )
 
-    def __str__(self):
+    def __str__(self) -> str:
         return ", ".join(repr(exc) for exc in self.exceptions)
 
-    def __repr__(self):
+    def __repr__(self) -> str:
         return f"<MultiError: {self}>"
 
+    # types: no-untyped-def error: Function is missing a type annotation
     def derive(self, __excs):
         # We use _collapse=False here to get ExceptionGroup semantics, since derive()
         # is part of the PEP 654 API
@@ -244,7 +357,9 @@ def derive(self, __excs):
         return exc
 
     @classmethod
-    def filter(cls, handler, root_exc):
+    def filter(
+        cls, handler: Callable[[BaseException], BaseException], root_exc: BaseException
+    ) -> BaseException | None:
         """Apply the given ``handler`` to all the exceptions in ``root_exc``.
 
         Args:
@@ -268,7 +383,9 @@ def filter(cls, handler, root_exc):
         return _filter_impl(handler, root_exc)
 
     @classmethod
-    def catch(cls, handler):
+    def catch(
+        cls, handler: Callable[[BaseException], BaseException]
+    ) -> MultiErrorCatcher:
         """Return a context manager that catches and re-throws exceptions
         after running :meth:`filter` on them.
 
@@ -286,6 +403,7 @@ def catch(cls, handler):
         return MultiErrorCatcher(handler)
 
 
+# types: type-arg error: Missing type parameters for generic type "ExceptionGroup"
 class NonBaseMultiError(MultiError, ExceptionGroup):
     pass
 
@@ -314,6 +432,8 @@ class NonBaseMultiError(MultiError, ExceptionGroup):
 #   https://github.com/pallets/jinja/blob/master/jinja2/debug.py
 
 try:
+    # types: import error: Cannot find implementation or library stub for module named "tputil"
+    # types: note: See https://mypy.readthedocs.io/en/stable/running_mypy.html#missing-imports
     import tputil
 except ImportError:
     have_tproxy = False
@@ -322,7 +442,8 @@ class NonBaseMultiError(MultiError, ExceptionGroup):
 
 if have_tproxy:
     # http://doc.pypy.org/en/latest/objspace-proxies.html
-    def copy_tb(base_tb, tb_next):
+    def copy_tb(base_tb: TracebackType, tb_next: TracebackType | None) -> tputil:
+        # types: no-untyped-def error: Function is missing a type annotation
         def controller(operation):
             # Rationale for pragma: I looked fairly carefully and tried a few
             # things, and AFAICT it's not actually possible to get any
@@ -397,7 +518,9 @@ def copy_tb(base_tb, tb_next):
             del new_tb, old_tb_frame
 
 
-def concat_tb(head, tail):
+def concat_tb(
+    head: TracebackType | None, tail: TracebackType | None
+) -> TracebackType | None:
     # We have to use an iterative algorithm here, because in the worst case
     # this might be a RecursionError stack that is by definition too deep to
     # process by recursion!
@@ -417,7 +540,9 @@ def concat_tb(head, tail):
 if "IPython" in sys.modules:
     import IPython
 
+    # types: attr-defined error: Module "IPython" does not explicitly export attribute "get_ipython"
     ip = IPython.get_ipython()
+    # types: ^^^^^
     if ip is not None:
         if ip.custom_exceptions != ():
             warnings.warn(
@@ -428,8 +553,15 @@ def concat_tb(head, tail):
                 category=RuntimeWarning,
             )
         else:
-
-            def trio_show_traceback(self, etype, value, tb, tb_offset=None):
+            # types: name-defined error: Name "Any" is not defined
+            # types: note: Did you forget to import it from "typing"? (Suggestion: "from typing import Any")
+            def trio_show_traceback(
+                self: Any,
+                etype: Any,
+                value: BaseException,
+                tb: TracebackType,
+                tb_offset: Any | None = None,
+            ) -> None:
                 # XX it would be better to integrate with IPython's fancy
                 # exception formatting stuff (and not ignore tb_offset)
                 print_exception(value)

From a3c89639020935c534098e7f6cab8a4014e434fe Mon Sep 17 00:00:00 2001
From: CoolCat467 <52022020+CoolCat467@users.noreply.github.com>
Date: Tue, 8 Aug 2023 20:10:18 -0500
Subject: [PATCH 02/13] Finish work on multierror

---
 trio/_core/_multierror.py | 179 +++++++++++---------------------------
 1 file changed, 53 insertions(+), 126 deletions(-)

diff --git a/trio/_core/_multierror.py b/trio/_core/_multierror.py
index 1791883aee..c3be839020 100644
--- a/trio/_core/_multierror.py
+++ b/trio/_core/_multierror.py
@@ -3,7 +3,7 @@
 import sys
 import warnings
 from collections.abc import Callable, Iterable
-from typing import TYPE_CHECKING, TypeVar
+from typing import TYPE_CHECKING, Any
 
 import attr
 
@@ -17,6 +17,7 @@
 if TYPE_CHECKING:
     from types import TracebackType
 
+    from mypy_extensions import DefaultNamedArg
     from typing_extensions import Self
 ################################################################
 # MultiError
@@ -24,7 +25,7 @@
 
 
 def _filter_impl(
-    handler: Callable[[BaseException], BaseException], root_exc: BaseException
+    handler: Callable[[BaseException], BaseException | None], root_exc: BaseException
 ) -> BaseException | None:
     # We have a tree of MultiError's, like:
     #
@@ -139,7 +140,7 @@ def push_tb_down(
 # frame show up in the traceback; otherwise, we leave no trace.)
 @attr.s(frozen=True)
 class MultiErrorCatcher:
-    _handler: Callable[[BaseException], BaseException] = attr.ib()
+    handler: Callable[[BaseException], BaseException | None] = attr.ib()
 
     def __enter__(self) -> None:
         pass
@@ -151,7 +152,7 @@ def __exit__(
         traceback: TracebackType | None,
     ) -> bool | None:
         if exc_value is not None:
-            filtered_exc = _filter_impl(self._handler, exc_value)
+            filtered_exc = _filter_impl(self.handler, exc_value)
 
             if filtered_exc is exc_value:
                 # Let the interpreter re-raise it
@@ -176,52 +177,13 @@ def __exit__(
         return False
 
 
-# types: type-arg error: Missing type parameters for generic type "BaseExceptionGroup"
-# types: note: Another file has errors: trio/_timeouts.py
-# types: note: Another file has errors: trio/_core/_entry_queue.py
-# types: note: Another file has errors: trio/_signals.py
-# types: note: Another file has errors: trio/_util.py
-# types: note: Another file has errors: trio/_subprocess_platform/waitid.py
-# types: note: Another file has errors: trio/testing/__init__.py
-# types: note: Another file has errors: trio/_core/_thread_cache.py
-# types: note: Another file has errors: trio/_channel.py
-# types: note: Another file has errors: trio/testing/_network.py
-# types: note: Another file has errors: trio/_core/_wakeup_socketpair.py
-# types: note: Another file has errors: trio/_subprocess.py
-# types: note: Another file has errors: trio/_core/_unbounded_queue.py
-# types: note: Another file has errors: trio/_path.py
-# types: note: Another file has errors: trio/testing/_memory_streams.py
-# types: note: Another file has errors: trio/_highlevel_open_unix_stream.py
-# types: note: Another file has errors: trio/testing/_checkpoints.py
-# types: note: Another file has errors: trio/_core/_traps.py
-# types: note: Another file has errors: trio/_highlevel_serve_listeners.py
-# types: note: Another file has errors: trio/_core/_generated_instrumentation.py
-# types: note: Another file has errors: trio/_socket.py
-# types: note: Another file has errors: trio/_core/_io_common.py
-# types: note: Another file has errors: trio/lowlevel.py
-# types: note: Another file has errors: trio/_core/_ki.py
-# types: note: Another file has errors: trio/_core/_asyncgens.py
-# types: note: Another file has errors: trio/_highlevel_ssl_helpers.py
-# types: note: Another file has errors: trio/_ssl.py
-# types: note: Another file has errors: trio/testing/_trio_test.py
-# types: note: Another file has errors: trio/_core/_parking_lot.py
-# types: note: Another file has errors: trio/_highlevel_open_tcp_listeners.py
-# types: note: Another file has errors: trio/testing/_check_streams.py
-# types: note: Another file has errors: trio/_highlevel_open_tcp_stream.py
-# types: note: Another file has errors: trio/_core/_generated_io_epoll.py
-# types: note: Another file has errors: trio/_core/_mock_clock.py
-# types: note: Another file has errors: trio/_sync.py
-# types: note: Another file has errors: trio/_threads.py
-# types: note: Another file has errors: trio/_dtls.py
-# types: note: Another file has errors: trio/_core/_run.py
-# types: note: Another file has errors: trio/__init__.py
-# types: note: Another file has errors: trio/_core/_generated_run.py
-# types: note: Another file has errors: trio/_highlevel_socket.py
-# types: note: Another file has errors: trio/_unix_pipes.py
-# types: note: Another file has errors: trio/_core/_io_epoll.py
-# types: note: Another file has errors: trio/testing/_sequencer.py
-# types: type-arg error: Missing type parameters for generic type "BaseExceptionGroup"
-class MultiError(BaseExceptionGroup):
+if TYPE_CHECKING:
+    _BaseExceptionGroup = BaseExceptionGroup[BaseException]
+else:
+    _BaseExceptionGroup = BaseExceptionGroup
+
+
+class MultiError(_BaseExceptionGroup):
     """An exception that contains other exceptions; also known as an
     "inception".
 
@@ -257,9 +219,9 @@ def __init__(
 
         super().__init__("multiple tasks failed", exceptions)
 
-    def __new__(
+    def __new__(  # type: ignore[misc]  # mypy says __new__ must return a class instance
         cls, exceptions: Iterable[BaseException], *, _collapse: bool = True
-    ) -> MultiError | Self:
+    ) -> NonBaseMultiError | MultiError | Self:
         exceptions = list(exceptions)
         for exc in exceptions:
             if not isinstance(exc, BaseException):
@@ -278,64 +240,29 @@ def __new__(
             # In an earlier version of the code, we didn't define __init__ and
             # simply set the `exceptions` attribute directly on the new object.
             # However, linters expect attributes to be initialized in __init__.
+            from_class: type[Self] | type[NonBaseMultiError] = cls
             if all(isinstance(exc, Exception) for exc in exceptions):
-                cls = NonBaseMultiError
-
-            return super().__new__(cls, "multiple tasks failed", exceptions)
-
-    # types: Error running mypy: Daemon crashed!
-    # types: Traceback (most recent call last):
-    # types:   File "mypy/suggestions.py", line 296, in restore_after
-    # types:   File "mypy/suggestions.py", line 267, in suggest
-    # types:   File "mypy/suggestions.py", line 502, in get_suggestion
-    # types:   File "mypy/suggestions.py", line 444, in find_best
-    # types:   File "mypy/suggestions.py", line 675, in try_type
-    # types:   File "mypy/server/update.py", line 314, in trigger
-    # types:   File "mypy/server/update.py", line 881, in propagate_changes_using_dependencies
-    # types:   File "mypy/server/update.py", line 1010, in reprocess_nodes
-    # types:   File "mypy/semanal_main.py", line 144, in semantic_analysis_for_targets
-    # types:   File "mypy/semanal_main.py", line 291, in process_top_level_function
-    # types:   File "mypy/semanal_main.py", line 349, in semantic_analyze_target
-    # types:   File "mypy/semanal.py", line 603, in refresh_partial
-    # types:   File "mypy/semanal.py", line 6453, in accept
-    # types:   File "mypy/errors.py", line 1177, in report_internal_error
-    # types:   File "mypy/semanal.py", line 6451, in accept
-    # types:   File "mypy/nodes.py", line 786, in accept
-    # types:   File "mypy/semanal.py", line 833, in visit_func_def
-    # types:   File "mypy/semanal.py", line 865, in analyze_func_def
-    # types:   File "mypy/typeanal.py", line 950, in visit_callable_type
-    # types:   File "mypy/typeanal.py", line 1522, in anal_type
-    # types:   File "mypy/types.py", line 2294, in accept
-    # types:   File "mypy/typeanal.py", line 1051, in visit_tuple_type
-    # types:   File "mypy/typeanal.py", line 1512, in anal_array
-    # types:   File "mypy/typeanal.py", line 1522, in anal_type
-    # types:   File "mypy/types.py", line 1917, in accept
-    # types:   File "mypy/typeanal.py", line 931, in visit_callable_type
-    # types:   File "mypy/typeanal.py", line 1469, in bind_function_type_variables
-    # types: AssertionError
-    # types: During handling of the above exception, another exception occurred:
-    # types: Traceback (most recent call last):
-    # types:   File "mypy/dmypy_server.py", line 234, in serve
-    # types:   File "mypy/dmypy_server.py", line 281, in run_command
-    # types:   File "mypy/dmypy_server.py", line 931, in cmd_suggest
-    # types:   File "mypy/suggestions.py", line 265, in suggest
-    # types:   File "/usr/lib/python3.11/contextlib.py", line 155, in __exit__
-    # types:     self.gen.throw(typ, value, traceback)
-    # types:   File "mypy/suggestions.py", line 298, in restore_after
-    # types:   File "mypy/suggestions.py", line 687, in reload
-    # types:   File "mypy/server/update.py", line 267, in update
-    # types:   File "mypy/server/update.py", line 369, in update_one
-    # types:   File "mypy/server/update.py", line 426, in update_module
-    # types:   File "mypy/server/astdiff.py", line 223, in snapshot_symbol_table
-    # types:   File "mypy/server/astdiff.py", line 236, in snapshot_definition
-    # types:   File "mypy/server/astdiff.py", line 315, in snapshot_type
-    # types:   File "mypy/types.py", line 1917, in accept
-    # types:   File "mypy/server/astdiff.py", line 439, in visit_callable_type
-    # types:   File "mypy/types.py", line 1900, in is_type_obj
-    # types:   File "mypy/nodes.py", line 3170, in is_metaclass
-    # types:   File "mypy/nodes.py", line 3180, in has_base
-    # types: AttributeError: attribute 'mro' of 'TypeInfo' undefined
-    def __reduce__(self):
+                from_class = NonBaseMultiError
+
+            # Mypy is really mad about the following line:
+            # Ignoring arg-type: 'Argument 3 to "__new__" of "BaseExceptionGroup" has incompatible type "list[BaseException]"; expected "Sequence[_BaseExceptionT_co]"'
+            # We have checked that exceptions is indeed a list of BaseException objects, this is fine.
+            # Ignoring type-var: 'Value of type variable "Self" of "__new__" of "BaseExceptionGroup" cannot be "object"'
+            # Not sure how mypy is getting 'object', this is also fine.
+            new_obj = super().__new__(from_class, "multiple tasks failed", exceptions)  # type: ignore[arg-type,type-var]
+            assert isinstance(new_obj, (cls, NonBaseMultiError))
+            return new_obj
+
+    def __reduce__(
+        self,
+    ) -> tuple[
+        Callable[
+            [type[Self], Iterable[BaseException], DefaultNamedArg(bool, "_collapse")],
+            NonBaseMultiError | MultiError | Self,
+        ],
+        tuple[type[Self], list[BaseException]],
+        dict[str, bool],
+    ]:
         return (
             self.__new__,
             (self.__class__, list(self.exceptions)),
@@ -348,8 +275,7 @@ def __str__(self) -> str:
     def __repr__(self) -> str:
         return f"<MultiError: {self}>"
 
-    # types: no-untyped-def error: Function is missing a type annotation
-    def derive(self, __excs):
+    def derive(self, __excs: list[BaseException]) -> MultiError:  # type: ignore[override]
         # We use _collapse=False here to get ExceptionGroup semantics, since derive()
         # is part of the PEP 654 API
         exc = MultiError(__excs, _collapse=False)
@@ -358,7 +284,9 @@ def derive(self, __excs):
 
     @classmethod
     def filter(
-        cls, handler: Callable[[BaseException], BaseException], root_exc: BaseException
+        cls,
+        handler: Callable[[BaseException], BaseException | None],
+        root_exc: BaseException,
     ) -> BaseException | None:
         """Apply the given ``handler`` to all the exceptions in ``root_exc``.
 
@@ -384,7 +312,7 @@ def filter(
 
     @classmethod
     def catch(
-        cls, handler: Callable[[BaseException], BaseException]
+        cls, handler: Callable[[BaseException], BaseException | None]
     ) -> MultiErrorCatcher:
         """Return a context manager that catches and re-throws exceptions
         after running :meth:`filter` on them.
@@ -403,9 +331,14 @@ def catch(
         return MultiErrorCatcher(handler)
 
 
-# types: type-arg error: Missing type parameters for generic type "ExceptionGroup"
-class NonBaseMultiError(MultiError, ExceptionGroup):
-    pass
+if TYPE_CHECKING:
+    _ExceptionGroup = ExceptionGroup[Exception]
+else:
+    _ExceptionGroup = ExceptionGroup
+
+
+class NonBaseMultiError(MultiError, _ExceptionGroup):
+    __slots__ = ()
 
 
 # Clean up exception printing:
@@ -432,8 +365,6 @@ class NonBaseMultiError(MultiError, ExceptionGroup):
 #   https://github.com/pallets/jinja/blob/master/jinja2/debug.py
 
 try:
-    # types: import error: Cannot find implementation or library stub for module named "tputil"
-    # types: note: See https://mypy.readthedocs.io/en/stable/running_mypy.html#missing-imports
     import tputil
 except ImportError:
     have_tproxy = False
@@ -443,8 +374,7 @@ class NonBaseMultiError(MultiError, ExceptionGroup):
 if have_tproxy:
     # http://doc.pypy.org/en/latest/objspace-proxies.html
     def copy_tb(base_tb: TracebackType, tb_next: TracebackType | None) -> tputil:
-        # types: no-untyped-def error: Function is missing a type annotation
-        def controller(operation):
+        def controller(operation: tputil.ProxyOperation) -> TracebackType | None | Any:
             # Rationale for pragma: I looked fairly carefully and tried a few
             # things, and AFAICT it's not actually possible to get any
             # 'opname' that isn't __getattr__ or __getattribute__. So there's
@@ -480,7 +410,7 @@ class CTraceback(ctypes.Structure):
             ("tb_lineno", ctypes.c_int),
         ]
 
-    def copy_tb(base_tb, tb_next):
+    def copy_tb(base_tb: TracebackType, tb_next: TracebackType) -> TracebackType:
         # TracebackType has no public constructor, so allocate one the hard way
         try:
             raise ValueError
@@ -540,9 +470,7 @@ def concat_tb(
 if "IPython" in sys.modules:
     import IPython
 
-    # types: attr-defined error: Module "IPython" does not explicitly export attribute "get_ipython"
-    ip = IPython.get_ipython()
-    # types: ^^^^^
+    ip = IPython.get_ipython()  # type: ignore[attr-defined]  # not explicitly exported
     if ip is not None:
         if ip.custom_exceptions != ():
             warnings.warn(
@@ -553,8 +481,7 @@ def concat_tb(
                 category=RuntimeWarning,
             )
         else:
-            # types: name-defined error: Name "Any" is not defined
-            # types: note: Did you forget to import it from "typing"? (Suggestion: "from typing import Any")
+
             def trio_show_traceback(
                 self: Any,
                 etype: Any,

From b21b2936e03320cffe5454697a67e7ab6e00f799 Mon Sep 17 00:00:00 2001
From: CoolCat467 <52022020+CoolCat467@users.noreply.github.com>
Date: Tue, 8 Aug 2023 20:28:34 -0500
Subject: [PATCH 03/13] Few fixes

---
 pyproject.toml            |  3 ++-
 trio/_core/_multierror.py | 22 +++++++++++++++-------
 2 files changed, 17 insertions(+), 8 deletions(-)

diff --git a/pyproject.toml b/pyproject.toml
index a23f7f5db9..9af051c5b6 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -52,8 +52,9 @@ module = [
     "trio._abc",
     "trio._core._entry_queue",
     "trio._core._local",
-    "trio._core._unbounded_queue",
+    "trio._core._multierror",
     "trio._core._thread_cache",
+    "trio._core._unbounded_queue",
     "trio._deprecate",
     "trio._dtls",
     "trio._file_io",
diff --git a/trio/_core/_multierror.py b/trio/_core/_multierror.py
index c3be839020..cd6f27eece 100644
--- a/trio/_core/_multierror.py
+++ b/trio/_core/_multierror.py
@@ -2,8 +2,8 @@
 
 import sys
 import warnings
-from collections.abc import Callable, Iterable
-from typing import TYPE_CHECKING, Any
+from collections.abc import Callable, Iterable, Sequence
+from typing import TYPE_CHECKING, Any, overload
 
 import attr
 
@@ -18,7 +18,7 @@
     from types import TracebackType
 
     from mypy_extensions import DefaultNamedArg
-    from typing_extensions import Self
+    from typing_extensions import Literal, Self
 ################################################################
 # MultiError
 ################################################################
@@ -221,7 +221,7 @@ def __init__(
 
     def __new__(  # type: ignore[misc]  # mypy says __new__ must return a class instance
         cls, exceptions: Iterable[BaseException], *, _collapse: bool = True
-    ) -> NonBaseMultiError | MultiError | Self:
+    ) -> NonBaseMultiError | Self:
         exceptions = list(exceptions)
         for exc in exceptions:
             if not isinstance(exc, BaseException):
@@ -231,7 +231,7 @@ def __new__(  # type: ignore[misc]  # mypy says __new__ must return a class inst
             # Python will implicitly call our __init__ on it again.  See
             # special handling in __init__.
             single = exceptions[0]
-            assert isinstance(single, MultiError)
+            assert isinstance(single, cls)
             return single
         else:
             # The base class __new__() implicitly invokes our __init__, which
@@ -275,10 +275,18 @@ def __str__(self) -> str:
     def __repr__(self) -> str:
         return f"<MultiError: {self}>"
 
-    def derive(self, __excs: list[BaseException]) -> MultiError:  # type: ignore[override]
+    @overload  # type: ignore[override]  # Basically mypy is mad return type is not exactly the same as superclass
+    def derive(self, __excs: Sequence[Exception]) -> NonBaseMultiError:
+        ...
+
+    @overload
+    def derive(self, __excs: Sequence[BaseException]) -> MultiError:
+        ...
+
+    def derive(self, __excs: Sequence[Exception | BaseException]) -> MultiError:
         # We use _collapse=False here to get ExceptionGroup semantics, since derive()
         # is part of the PEP 654 API
-        exc = MultiError(__excs, _collapse=False)
+        exc = MultiError(list(__excs), _collapse=False)
         exc.collapse = self.collapse
         return exc
 

From e0f7a9cac32647c303af28f101600ade0331a45e Mon Sep 17 00:00:00 2001
From: CoolCat467 <52022020+CoolCat467@users.noreply.github.com>
Date: Tue, 8 Aug 2023 21:30:55 -0500
Subject: [PATCH 04/13] Fix incorrect assumptions

---
 trio/_core/_multierror.py | 45 +++++++++++++++++----------------------
 1 file changed, 20 insertions(+), 25 deletions(-)

diff --git a/trio/_core/_multierror.py b/trio/_core/_multierror.py
index cd6f27eece..3a621b8bae 100644
--- a/trio/_core/_multierror.py
+++ b/trio/_core/_multierror.py
@@ -3,7 +3,7 @@
 import sys
 import warnings
 from collections.abc import Callable, Iterable, Sequence
-from typing import TYPE_CHECKING, Any, overload
+from typing import TYPE_CHECKING, Any, cast, overload
 
 import attr
 
@@ -18,7 +18,7 @@
     from types import TracebackType
 
     from mypy_extensions import DefaultNamedArg
-    from typing_extensions import Literal, Self
+    from typing_extensions import Self
 ################################################################
 # MultiError
 ################################################################
@@ -140,7 +140,7 @@ def push_tb_down(
 # frame show up in the traceback; otherwise, we leave no trace.)
 @attr.s(frozen=True)
 class MultiErrorCatcher:
-    handler: Callable[[BaseException], BaseException | None] = attr.ib()
+    _handler: Callable[[BaseException], BaseException | None] = attr.ib()
 
     def __enter__(self) -> None:
         pass
@@ -152,7 +152,7 @@ def __exit__(
         traceback: TracebackType | None,
     ) -> bool | None:
         if exc_value is not None:
-            filtered_exc = _filter_impl(self.handler, exc_value)
+            filtered_exc = _filter_impl(self._handler, exc_value)
 
             if filtered_exc is exc_value:
                 # Let the interpreter re-raise it
@@ -221,7 +221,7 @@ def __init__(
 
     def __new__(  # type: ignore[misc]  # mypy says __new__ must return a class instance
         cls, exceptions: Iterable[BaseException], *, _collapse: bool = True
-    ) -> NonBaseMultiError | Self:
+    ) -> NonBaseMultiError | Self | BaseException:
         exceptions = list(exceptions)
         for exc in exceptions:
             if not isinstance(exc, BaseException):
@@ -230,9 +230,7 @@ def __new__(  # type: ignore[misc]  # mypy says __new__ must return a class inst
             # If this lone object happens to itself be a MultiError, then
             # Python will implicitly call our __init__ on it again.  See
             # special handling in __init__.
-            single = exceptions[0]
-            assert isinstance(single, cls)
-            return single
+            return exceptions[0]
         else:
             # The base class __new__() implicitly invokes our __init__, which
             # is what we want.
@@ -255,14 +253,7 @@ def __new__(  # type: ignore[misc]  # mypy says __new__ must return a class inst
 
     def __reduce__(
         self,
-    ) -> tuple[
-        Callable[
-            [type[Self], Iterable[BaseException], DefaultNamedArg(bool, "_collapse")],
-            NonBaseMultiError | MultiError | Self,
-        ],
-        tuple[type[Self], list[BaseException]],
-        dict[str, bool],
-    ]:
+    ) -> tuple[object, tuple[type[Self], list[BaseException]], dict[str, bool],]:
         return (
             self.__new__,
             (self.__class__, list(self.exceptions)),
@@ -283,7 +274,9 @@ def derive(self, __excs: Sequence[Exception]) -> NonBaseMultiError:
     def derive(self, __excs: Sequence[BaseException]) -> MultiError:
         ...
 
-    def derive(self, __excs: Sequence[Exception | BaseException]) -> MultiError:
+    def derive(
+        self, __excs: Sequence[Exception | BaseException]
+    ) -> NonBaseMultiError | MultiError:
         # We use _collapse=False here to get ExceptionGroup semantics, since derive()
         # is part of the PEP 654 API
         exc = MultiError(list(__excs), _collapse=False)
@@ -381,8 +374,8 @@ class NonBaseMultiError(MultiError, _ExceptionGroup):
 
 if have_tproxy:
     # http://doc.pypy.org/en/latest/objspace-proxies.html
-    def copy_tb(base_tb: TracebackType, tb_next: TracebackType | None) -> tputil:
-        def controller(operation: tputil.ProxyOperation) -> TracebackType | None | Any:
+    def copy_tb(base_tb: TracebackType, tb_next: TracebackType | None) -> TracebackType:
+        def controller(operation: tputil.ProxyOperation) -> Any | None:
             # Rationale for pragma: I looked fairly carefully and tried a few
             # things, and AFAICT it's not actually possible to get any
             # 'opname' that isn't __getattr__ or __getattribute__. So there's
@@ -394,9 +387,11 @@ def controller(operation: tputil.ProxyOperation) -> TracebackType | None | Any:
             ]:  # pragma: no cover
                 if operation.args[0] == "tb_next":
                     return tb_next
-            return operation.delegate()
+            return operation.delegate()  # Deligate is reverting to original behaviour
 
-        return tputil.make_proxy(controller, type(base_tb), base_tb)
+        return cast(
+            TracebackType, tputil.make_proxy(controller, type(base_tb), base_tb)
+        )  # Returns proxy to traceback
 
 else:
     # ctypes it is
@@ -418,7 +413,7 @@ class CTraceback(ctypes.Structure):
             ("tb_lineno", ctypes.c_int),
         ]
 
-    def copy_tb(base_tb: TracebackType, tb_next: TracebackType) -> TracebackType:
+    def copy_tb(base_tb: TracebackType, tb_next: TracebackType | None) -> TracebackType:
         # TracebackType has no public constructor, so allocate one the hard way
         try:
             raise ValueError
@@ -491,11 +486,11 @@ def concat_tb(
         else:
 
             def trio_show_traceback(
-                self: Any,
-                etype: Any,
+                self: IPython.core.interactiveshell.InteractiveShell,
+                etype: type[BaseException],
                 value: BaseException,
                 tb: TracebackType,
-                tb_offset: Any | None = None,
+                tb_offset: int | None = None,
             ) -> None:
                 # XX it would be better to integrate with IPython's fancy
                 # exception formatting stuff (and not ignore tb_offset)

From b52d133cf4b4cf25458cb2cbb4da89ac467f62eb Mon Sep 17 00:00:00 2001
From: CoolCat467 <52022020+CoolCat467@users.noreply.github.com>
Date: Tue, 8 Aug 2023 21:32:50 -0500
Subject: [PATCH 05/13] Remove unused import

---
 trio/_core/_multierror.py | 1 -
 1 file changed, 1 deletion(-)

diff --git a/trio/_core/_multierror.py b/trio/_core/_multierror.py
index 3a621b8bae..6194127e07 100644
--- a/trio/_core/_multierror.py
+++ b/trio/_core/_multierror.py
@@ -17,7 +17,6 @@
 if TYPE_CHECKING:
     from types import TracebackType
 
-    from mypy_extensions import DefaultNamedArg
     from typing_extensions import Self
 ################################################################
 # MultiError

From d49b65e2708bc686a1a1ae9be9e839aa4b7d0ea3 Mon Sep 17 00:00:00 2001
From: CoolCat467 <52022020+CoolCat467@users.noreply.github.com>
Date: Tue, 8 Aug 2023 21:48:02 -0500
Subject: [PATCH 06/13] Fix issues from CI

---
 trio/_core/_multierror.py | 23 ++++++++++++-----------
 1 file changed, 12 insertions(+), 11 deletions(-)

diff --git a/trio/_core/_multierror.py b/trio/_core/_multierror.py
index 6194127e07..ca671b175b 100644
--- a/trio/_core/_multierror.py
+++ b/trio/_core/_multierror.py
@@ -3,6 +3,7 @@
 import sys
 import warnings
 from collections.abc import Callable, Iterable, Sequence
+from types import TracebackType
 from typing import TYPE_CHECKING, Any, cast, overload
 
 import attr
@@ -15,8 +16,6 @@
     from traceback import print_exception
 
 if TYPE_CHECKING:
-    from types import TracebackType
-
     from typing_extensions import Self
 ################################################################
 # MultiError
@@ -241,12 +240,9 @@ def __new__(  # type: ignore[misc]  # mypy says __new__ must return a class inst
             if all(isinstance(exc, Exception) for exc in exceptions):
                 from_class = NonBaseMultiError
 
-            # Mypy is really mad about the following line:
             # Ignoring arg-type: 'Argument 3 to "__new__" of "BaseExceptionGroup" has incompatible type "list[BaseException]"; expected "Sequence[_BaseExceptionT_co]"'
             # We have checked that exceptions is indeed a list of BaseException objects, this is fine.
-            # Ignoring type-var: 'Value of type variable "Self" of "__new__" of "BaseExceptionGroup" cannot be "object"'
-            # Not sure how mypy is getting 'object', this is also fine.
-            new_obj = super().__new__(from_class, "multiple tasks failed", exceptions)  # type: ignore[arg-type,type-var]
+            new_obj = super().__new__(from_class, "multiple tasks failed", exceptions)  # type: ignore[arg-type]
             assert isinstance(new_obj, (cls, NonBaseMultiError))
             return new_obj
 
@@ -372,6 +368,9 @@ class NonBaseMultiError(MultiError, _ExceptionGroup):
     have_tproxy = True
 
 if have_tproxy:
+    if TYPE_CHECKING:
+        import tputil
+
     # http://doc.pypy.org/en/latest/objspace-proxies.html
     def copy_tb(base_tb: TracebackType, tb_next: TracebackType | None) -> TracebackType:
         def controller(operation: tputil.ProxyOperation) -> Any | None:
@@ -430,14 +429,14 @@ def copy_tb(base_tb: TracebackType, tb_next: TracebackType | None) -> TracebackT
         # which it already is, so we're done. Otherwise, we have to actually
         # do some work:
         if tb_next is not None:
-            _ctypes.Py_INCREF(tb_next)
+            _ctypes.Py_INCREF(tb_next)  # type: ignore[attr-defined]
             c_new_tb.tb_next = id(tb_next)
 
         assert c_new_tb.tb_frame is not None
-        _ctypes.Py_INCREF(base_tb.tb_frame)
+        _ctypes.Py_INCREF(base_tb.tb_frame)  # type: ignore[attr-defined]
         old_tb_frame = new_tb.tb_frame
         c_new_tb.tb_frame = id(base_tb.tb_frame)
-        _ctypes.Py_DECREF(old_tb_frame)
+        _ctypes.Py_DECREF(old_tb_frame)  # type: ignore[attr-defined]
 
         c_new_tb.tb_lasti = base_tb.tb_lasti
         c_new_tb.tb_lineno = base_tb.tb_lineno
@@ -472,7 +471,7 @@ def concat_tb(
 if "IPython" in sys.modules:
     import IPython
 
-    ip = IPython.get_ipython()  # type: ignore[attr-defined]  # not explicitly exported
+    ip = IPython.get_ipython()
     if ip is not None:
         if ip.custom_exceptions != ():
             warnings.warn(
@@ -521,7 +520,9 @@ def trio_show_traceback(
 
     assert sys.excepthook is apport_python_hook.apport_excepthook
 
-    def replacement_excepthook(etype, value, tb):
+    def replacement_excepthook(
+        etype: type[BaseException], value: BaseException, tb: TracebackType
+    ) -> None:
         sys.stderr.write("".join(format_exception(etype, value, tb)))
 
     fake_sys = ModuleType("trio_fake_sys")

From 15a629ad7566599fcdc5fbaf70041a3254166de6 Mon Sep 17 00:00:00 2001
From: CoolCat467 <52022020+CoolCat467@users.noreply.github.com>
Date: Tue, 8 Aug 2023 22:10:47 -0500
Subject: [PATCH 07/13] More fixes from CI

---
 trio/_core/_multierror.py | 57 +++++++++++++++++----------------------
 1 file changed, 25 insertions(+), 32 deletions(-)

diff --git a/trio/_core/_multierror.py b/trio/_core/_multierror.py
index ca671b175b..bb9e5d09ee 100644
--- a/trio/_core/_multierror.py
+++ b/trio/_core/_multierror.py
@@ -363,35 +363,6 @@ class NonBaseMultiError(MultiError, _ExceptionGroup):
 try:
     import tputil
 except ImportError:
-    have_tproxy = False
-else:
-    have_tproxy = True
-
-if have_tproxy:
-    if TYPE_CHECKING:
-        import tputil
-
-    # http://doc.pypy.org/en/latest/objspace-proxies.html
-    def copy_tb(base_tb: TracebackType, tb_next: TracebackType | None) -> TracebackType:
-        def controller(operation: tputil.ProxyOperation) -> Any | None:
-            # Rationale for pragma: I looked fairly carefully and tried a few
-            # things, and AFAICT it's not actually possible to get any
-            # 'opname' that isn't __getattr__ or __getattribute__. So there's
-            # no missing test we could add, and no value in coverage nagging
-            # us about adding one.
-            if operation.opname in [
-                "__getattribute__",
-                "__getattr__",
-            ]:  # pragma: no cover
-                if operation.args[0] == "tb_next":
-                    return tb_next
-            return operation.delegate()  # Deligate is reverting to original behaviour
-
-        return cast(
-            TracebackType, tputil.make_proxy(controller, type(base_tb), base_tb)
-        )  # Returns proxy to traceback
-
-else:
     # ctypes it is
     import ctypes
 
@@ -417,6 +388,7 @@ def copy_tb(base_tb: TracebackType, tb_next: TracebackType | None) -> TracebackT
             raise ValueError
         except ValueError as exc:
             new_tb = exc.__traceback__
+            assert new_tb is not None
         c_new_tb = CTraceback.from_address(id(new_tb))
 
         # At the C level, tb_next either pointer to the next traceback or is
@@ -442,12 +414,33 @@ def copy_tb(base_tb: TracebackType, tb_next: TracebackType | None) -> TracebackT
         c_new_tb.tb_lineno = base_tb.tb_lineno
 
         try:
-            return new_tb
+            return cast(TracebackType, new_tb)
         finally:
             # delete references from locals to avoid creating cycles
             # see test_MultiError_catch_doesnt_create_cyclic_garbage
             del new_tb, old_tb_frame
 
+else:
+    # http://doc.pypy.org/en/latest/objspace-proxies.html
+    def copy_tb(base_tb: TracebackType, tb_next: TracebackType | None) -> TracebackType:
+        def controller(operation: tputil.ProxyOperation) -> Any | None:
+            # Rationale for pragma: I looked fairly carefully and tried a few
+            # things, and AFAICT it's not actually possible to get any
+            # 'opname' that isn't __getattr__ or __getattribute__. So there's
+            # no missing test we could add, and no value in coverage nagging
+            # us about adding one.
+            if operation.opname in [
+                "__getattribute__",
+                "__getattr__",
+            ]:  # pragma: no cover
+                if operation.args[0] == "tb_next":
+                    return tb_next
+            return operation.delegate()  # Deligate is reverting to original behaviour
+
+        return cast(
+            TracebackType, tputil.make_proxy(controller, type(base_tb), base_tb)
+        )  # Returns proxy to traceback
+
 
 def concat_tb(
     head: TracebackType | None, tail: TracebackType | None
@@ -521,11 +514,11 @@ def trio_show_traceback(
     assert sys.excepthook is apport_python_hook.apport_excepthook
 
     def replacement_excepthook(
-        etype: type[BaseException], value: BaseException, tb: TracebackType
+        etype: type[BaseException], value: BaseException, tb: TracebackType | None
     ) -> None:
         sys.stderr.write("".join(format_exception(etype, value, tb)))
 
     fake_sys = ModuleType("trio_fake_sys")
     fake_sys.__dict__.update(sys.__dict__)
-    fake_sys.__excepthook__ = replacement_excepthook  # type: ignore
+    fake_sys.__excepthook__ = replacement_excepthook
     apport_python_hook.sys = fake_sys

From 77cf68304151565436fee8b2322a4ffe51b37626 Mon Sep 17 00:00:00 2001
From: CoolCat467 <52022020+CoolCat467@users.noreply.github.com>
Date: Tue, 8 Aug 2023 22:18:48 -0500
Subject: [PATCH 08/13] Fixes from CI no. 3

---
 trio/_core/_multierror.py | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/trio/_core/_multierror.py b/trio/_core/_multierror.py
index bb9e5d09ee..8cbf411fc6 100644
--- a/trio/_core/_multierror.py
+++ b/trio/_core/_multierror.py
@@ -261,7 +261,7 @@ def __str__(self) -> str:
     def __repr__(self) -> str:
         return f"<MultiError: {self}>"
 
-    @overload  # type: ignore[override]  # Basically mypy is mad return type is not exactly the same as superclass
+    @overload
     def derive(self, __excs: Sequence[Exception]) -> NonBaseMultiError:
         ...
 
@@ -414,16 +414,19 @@ def copy_tb(base_tb: TracebackType, tb_next: TracebackType | None) -> TracebackT
         c_new_tb.tb_lineno = base_tb.tb_lineno
 
         try:
-            return cast(TracebackType, new_tb)
+            return new_tb
         finally:
             # delete references from locals to avoid creating cycles
             # see test_MultiError_catch_doesnt_create_cyclic_garbage
             del new_tb, old_tb_frame
 
 else:
+    if TYPE_CHECKING:
+        from tputil import ProxyOperation
+
     # http://doc.pypy.org/en/latest/objspace-proxies.html
     def copy_tb(base_tb: TracebackType, tb_next: TracebackType | None) -> TracebackType:
-        def controller(operation: tputil.ProxyOperation) -> Any | None:
+        def controller(operation: ProxyOperation) -> Any | None:
             # Rationale for pragma: I looked fairly carefully and tried a few
             # things, and AFAICT it's not actually possible to get any
             # 'opname' that isn't __getattr__ or __getattribute__. So there's
@@ -516,9 +519,11 @@ def trio_show_traceback(
     def replacement_excepthook(
         etype: type[BaseException], value: BaseException, tb: TracebackType | None
     ) -> None:
-        sys.stderr.write("".join(format_exception(etype, value, tb)))
+        # This does work, it's an overloaded function
+        sys.stderr.write("".join(format_exception(etype, value, tb)))  # type: ignore[arg-type]
 
     fake_sys = ModuleType("trio_fake_sys")
     fake_sys.__dict__.update(sys.__dict__)
-    fake_sys.__excepthook__ = replacement_excepthook
+    # Fake does not have __excepthook__ attribute, but we are about to replace real sys
+    fake_sys.__excepthook__ = replacement_excepthook  # type: ignore[attr-defined]
     apport_python_hook.sys = fake_sys

From 9b2c32d5b26163dbdd021d0bddc0f2648823d74a Mon Sep 17 00:00:00 2001
From: CoolCat467 <52022020+CoolCat467@users.noreply.github.com>
Date: Tue, 8 Aug 2023 22:29:08 -0500
Subject: [PATCH 09/13] Ignore `tputil.ProxyOperation` not being able to import
 error (lies)

---
 trio/_core/_multierror.py | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/trio/_core/_multierror.py b/trio/_core/_multierror.py
index 8cbf411fc6..a1e6545a86 100644
--- a/trio/_core/_multierror.py
+++ b/trio/_core/_multierror.py
@@ -421,12 +421,10 @@ def copy_tb(base_tb: TracebackType, tb_next: TracebackType | None) -> TracebackT
             del new_tb, old_tb_frame
 
 else:
-    if TYPE_CHECKING:
-        from tputil import ProxyOperation
-
     # http://doc.pypy.org/en/latest/objspace-proxies.html
     def copy_tb(base_tb: TracebackType, tb_next: TracebackType | None) -> TracebackType:
-        def controller(operation: ProxyOperation) -> Any | None:
+        # Mypy refuses to believe that ProxyOperation can be imported properly
+        def controller(operation: tputil.ProxyOperation) -> Any | None:  # type: ignore[no-any-unimported]
             # Rationale for pragma: I looked fairly carefully and tried a few
             # things, and AFAICT it's not actually possible to get any
             # 'opname' that isn't __getattr__ or __getattribute__. So there's

From 5ad1cab84968e3ce6384e95abb433802e0448c43 Mon Sep 17 00:00:00 2001
From: CoolCat467 <52022020+CoolCat467@users.noreply.github.com>
Date: Wed, 9 Aug 2023 08:58:33 -0500
Subject: [PATCH 10/13] Fixes suggested by @A5rocks

---
 trio/_core/_multierror.py | 18 ++++++++++--------
 1 file changed, 10 insertions(+), 8 deletions(-)

diff --git a/trio/_core/_multierror.py b/trio/_core/_multierror.py
index a1e6545a86..c09e5b2d23 100644
--- a/trio/_core/_multierror.py
+++ b/trio/_core/_multierror.py
@@ -204,8 +204,10 @@ class MultiError(_BaseExceptionGroup):
 
     """
 
+    __slots__ = ("collapse",)
+
     def __init__(
-        self, exceptions: list[BaseException], *, _collapse: bool = True
+        self, exceptions: Sequence[BaseException], *, _collapse: bool = True
     ) -> None:
         self.collapse = _collapse
 
@@ -218,7 +220,7 @@ def __init__(
         super().__init__("multiple tasks failed", exceptions)
 
     def __new__(  # type: ignore[misc]  # mypy says __new__ must return a class instance
-        cls, exceptions: Iterable[BaseException], *, _collapse: bool = True
+        cls, exceptions: Sequence[BaseException], *, _collapse: bool = True
     ) -> NonBaseMultiError | Self | BaseException:
         exceptions = list(exceptions)
         for exc in exceptions:
@@ -248,7 +250,7 @@ def __new__(  # type: ignore[misc]  # mypy says __new__ must return a class inst
 
     def __reduce__(
         self,
-    ) -> tuple[object, tuple[type[Self], list[BaseException]], dict[str, bool],]:
+    ) -> tuple[object, tuple[type[Self], list[BaseException]], dict[str, bool]]:
         return (
             self.__new__,
             (self.__class__, list(self.exceptions)),
@@ -262,19 +264,19 @@ def __repr__(self) -> str:
         return f"<MultiError: {self}>"
 
     @overload
-    def derive(self, __excs: Sequence[Exception]) -> NonBaseMultiError:
+    def derive(self, excs: Sequence[Exception], /) -> NonBaseMultiError:
         ...
 
     @overload
-    def derive(self, __excs: Sequence[BaseException]) -> MultiError:
+    def derive(self, excs: Sequence[BaseException], /) -> MultiError:
         ...
 
     def derive(
-        self, __excs: Sequence[Exception | BaseException]
+        self, excs: Sequence[Exception | BaseException], /
     ) -> NonBaseMultiError | MultiError:
         # We use _collapse=False here to get ExceptionGroup semantics, since derive()
         # is part of the PEP 654 API
-        exc = MultiError(list(__excs), _collapse=False)
+        exc = MultiError(excs, _collapse=False)
         exc.collapse = self.collapse
         return exc
 
@@ -522,6 +524,6 @@ def replacement_excepthook(
 
     fake_sys = ModuleType("trio_fake_sys")
     fake_sys.__dict__.update(sys.__dict__)
-    # Fake does not have __excepthook__ attribute, but we are about to replace real sys
+    # Fake does have __excepthook__ after __dict__ update, but type checkers don't recognize this
     fake_sys.__excepthook__ = replacement_excepthook  # type: ignore[attr-defined]
     apport_python_hook.sys = fake_sys

From 073ecb7278a200293e92a9bf931838200261985a Mon Sep 17 00:00:00 2001
From: CoolCat467 <52022020+CoolCat467@users.noreply.github.com>
Date: Wed, 9 Aug 2023 09:02:41 -0500
Subject: [PATCH 11/13] Remove unused import

---
 trio/_core/_multierror.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/trio/_core/_multierror.py b/trio/_core/_multierror.py
index c09e5b2d23..e1854184cf 100644
--- a/trio/_core/_multierror.py
+++ b/trio/_core/_multierror.py
@@ -2,7 +2,7 @@
 
 import sys
 import warnings
-from collections.abc import Callable, Iterable, Sequence
+from collections.abc import Callable, Sequence
 from types import TracebackType
 from typing import TYPE_CHECKING, Any, cast, overload
 

From dd2825a50773aca6317b9d59a0632f6683ed5b9c Mon Sep 17 00:00:00 2001
From: CoolCat467 <CoolCat467@users.noreply.github.com>
Date: Wed, 9 Aug 2023 10:46:56 -0500
Subject: [PATCH 12/13] Remove slots, causes test failures

---
 trio/_core/_multierror.py | 2 --
 1 file changed, 2 deletions(-)

diff --git a/trio/_core/_multierror.py b/trio/_core/_multierror.py
index e1854184cf..1dd675f474 100644
--- a/trio/_core/_multierror.py
+++ b/trio/_core/_multierror.py
@@ -204,8 +204,6 @@ class MultiError(_BaseExceptionGroup):
 
     """
 
-    __slots__ = ("collapse",)
-
     def __init__(
         self, exceptions: Sequence[BaseException], *, _collapse: bool = True
     ) -> None:

From 7a2ec85d9c7e078304ac0632af7aefef8485338b Mon Sep 17 00:00:00 2001
From: jakkdl <h6+github@pm.me>
Date: Mon, 14 Aug 2023 14:06:05 +0200
Subject: [PATCH 13/13] remove type: ignore no-any-unimported for now

---
 trio/_core/_multierror.py | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/trio/_core/_multierror.py b/trio/_core/_multierror.py
index 1dd675f474..6e4cb8b923 100644
--- a/trio/_core/_multierror.py
+++ b/trio/_core/_multierror.py
@@ -424,7 +424,8 @@ def copy_tb(base_tb: TracebackType, tb_next: TracebackType | None) -> TracebackT
     # http://doc.pypy.org/en/latest/objspace-proxies.html
     def copy_tb(base_tb: TracebackType, tb_next: TracebackType | None) -> TracebackType:
         # Mypy refuses to believe that ProxyOperation can be imported properly
-        def controller(operation: tputil.ProxyOperation) -> Any | None:  # type: ignore[no-any-unimported]
+        # TODO: will need no-any-unimported if/when that's toggled on
+        def controller(operation: tputil.ProxyOperation) -> Any | None:
             # Rationale for pragma: I looked fairly carefully and tried a few
             # things, and AFAICT it's not actually possible to get any
             # 'opname' that isn't __getattr__ or __getattribute__. So there's