From fe780a04a230c006136a6a84956e847dca4f630e Mon Sep 17 00:00:00 2001
From: Gnome <david2005thomas@gmail.com>
Date: Thu, 2 Sep 2021 13:07:07 +0100
Subject: [PATCH] Add some basic error handling for registration

---
 discord/ext/commands/bot.py    |  2 --
 discord/ext/commands/core.py   | 10 ++++++----
 discord/ext/commands/errors.py | 19 +++++++++++++++++++
 3 files changed, 25 insertions(+), 6 deletions(-)

diff --git a/discord/ext/commands/bot.py b/discord/ext/commands/bot.py
index e1a553e9..885fa3b3 100644
--- a/discord/ext/commands/bot.py
+++ b/discord/ext/commands/bot.py
@@ -1130,8 +1130,6 @@ class BotBase(GroupMixin):
         command = self.get_command(command_name)
         if command is None:
             raise errors.CommandNotFound(f'Command "{command_name}" is not found')
-        elif not command.slash_command:
-            return
 
         # Ensure the interaction channel is usable
         channel = interaction.channel
diff --git a/discord/ext/commands/core.py b/discord/ext/commands/core.py
index ea94a9b5..b51d67d2 100644
--- a/discord/ext/commands/core.py
+++ b/discord/ext/commands/core.py
@@ -1211,10 +1211,12 @@ class Command(_BaseCommand, Generic[CogT, P, T]):
                 annotation, origin = annotation.__args__[0], None
 
             if origin is None:
-                option["type"] = next(
-                    (num for t, num in application_option_type_lookup.items()
-                    if issubclass(annotation, t)), 3
-                )
+                generator = (num for t, num in application_option_type_lookup.items() if issubclass(annotation, t))
+                try:
+                    option["type"] = next(generator, 3)
+                except Exception as err:
+                    raise ApplicationCommandRegistrationError(self)
+
             elif origin is Literal and len(origin.__args__) <= 25: # type: ignore
                 option["choices"] = [{
                     "name": literal_value,
diff --git a/discord/ext/commands/errors.py b/discord/ext/commands/errors.py
index 93834385..01dbaee2 100644
--- a/discord/ext/commands/errors.py
+++ b/discord/ext/commands/errors.py
@@ -33,6 +33,7 @@ if TYPE_CHECKING:
 
     from .converter import Converter
     from .context import Context
+    from .core import Command
     from .cooldowns import Cooldown, BucketType
     from .flags import Flag
     from discord.abc import GuildChannel
@@ -93,6 +94,7 @@ __all__ = (
     'ExtensionFailed',
     'ExtensionNotFound',
     'CommandRegistrationError',
+    'ApplicationCommandRegistrationError',
     'FlagError',
     'BadFlagArgument',
     'MissingFlagArgument',
@@ -915,6 +917,23 @@ class CommandRegistrationError(ClientException):
         type_ = 'alias' if alias_conflict else 'command'
         super().__init__(f'The {type_} {name} is already an existing command or alias.')
 
+class ApplicationCommandRegistrationError(ClientException):
+    """An exception raised when a command cannot be converted to an
+    application command.
+
+    This inherits from :exc:`discord.ClientException`
+
+    .. versionadded:: 2.0
+
+    Attributes
+    ----------
+    command: :class:`Command`
+        The command that failed to be converted.
+    """
+    def __init__(self, command: Command) -> None:
+        self.command = command
+        super().__init__(f"{command.qualified_name} failed to converted to an application command.")
+
 class FlagError(BadArgument):
     """The base exception type for all flag parsing related errors.