exhaustiveness checks on literals are now possible with the move to py38

pylib/anki/rsbackend.py

@@ -32,7 +32,6 @@ from anki.dbproxy import Row as DBRow
 from anki.dbproxy import ValueForDB
 from anki.fluent_pb2 import FluentString as TR
 from anki.rsbackend_gen import RustBackendGenerated
-from anki.types import assert_impossible_literal
 
 if TYPE_CHECKING:
     from anki.fluent_pb2 import FluentStringValue as TRValue

pylib/anki/types.py

@@ -1,16 +1,5 @@
-import enum
+from typing import NoReturn
-from typing import Any, NoReturn
 
 
-class _Impossible(enum.Enum):
+def assert_exhaustive(arg: NoReturn) -> NoReturn:
-    pass
-
-
-def assert_impossible(arg: NoReturn) -> NoReturn:
-    raise Exception(f"unexpected arg received: {type(arg)} {arg}")
-
-
-# mypy is not yet smart enough to do exhaustiveness checking on literal types,
-# so this will fail at runtime instead of typecheck time :-(
-def assert_impossible_literal(arg: Any) -> NoReturn:
     raise Exception(f"unexpected arg received: {type(arg)} {arg}")

qt/aqt/mediasync.py

@@ -16,7 +16,7 @@ from anki.rsbackend import (
     NetworkError,
     ProgressKind,
 )
-from anki.types import assert_impossible
+from anki.types import assert_exhaustive
 from anki.utils import intTime
 from aqt import gui_hooks
 from aqt.qt import QDialog, QDialogButtonBox, QPushButton, QTextCursor, QTimer, qconnect
@@ -206,7 +206,7 @@ class MediaSyncDialog(QDialog):
         elif isinstance(entry.entry, MediaSyncProgress):
             txt = self._logentry_to_text(entry.entry)
         else:
-            assert_impossible(entry.entry)
+            assert_exhaustive(entry.entry)
         return self._time_and_text(entry.time, txt)
 
     def _logentry_to_text(self, e: MediaSyncProgress) -> str: