Allow Transformer.transform to be synchronous as well.

discord/app_commands/transformers.py

@@ -48,7 +48,7 @@ from .errors import AppCommandError, TransformerError
 from .models import AppCommandChannel, AppCommandThread, Choice
 from ..channel import StageChannel, StoreChannel, VoiceChannel, TextChannel, CategoryChannel
 from ..enums import AppCommandOptionType, ChannelType
-from ..utils import MISSING
+from ..utils import MISSING, maybe_coroutine
 from ..user import User
 from ..role import Role
 from ..member import Member
@@ -137,7 +137,8 @@ class CommandParameter:
                 return choice
 
             try:
-                return await self._annotation.transform(interaction, value)
+                # ParamSpec doesn't understand that transform is a callable since it's unbound
+                return await maybe_coroutine(self._annotation.transform, interaction, value)  # type: ignore
             except AppCommandError:
                 raise
             except Exception as e:
@@ -224,7 +225,7 @@ class Transformer:
 
     @classmethod
     async def transform(cls, interaction: Interaction, value: Any) -> Any:
-        """|coro|
+        """|maybecoro|
 
         Transforms the converted option value into another value.