From 629f36e7d78f034580572dc93659cae9082b48fe Mon Sep 17 00:00:00 2001
From: Rapptz <rapptz@gmail.com>
Date: Tue, 5 Apr 2022 06:40:31 -0400
Subject: [PATCH] [commands] Add fallback behaviour to the default parameter
 instances

This allows users to explicitly override the default annotation for
CurrentAuthor and CurrentChannel since they're wider than what most
users would expect
---
 discord/ext/commands/core.py       | 11 ++++++++++-
 discord/ext/commands/parameters.py | 18 +++++++++++++++++-
 2 files changed, 27 insertions(+), 2 deletions(-)

diff --git a/discord/ext/commands/core.py b/discord/ext/commands/core.py
index cf1d8ff88..3e2eb4688 100644
--- a/discord/ext/commands/core.py
+++ b/discord/ext/commands/core.py
@@ -138,7 +138,16 @@ def get_signature_parameters(
         default = parameter.default
         if isinstance(default, Parameter):  # update from the default
             if default.annotation is not Parameter.empty:
-                parameter._annotation = default.annotation
+                # There are a few cases to care about here.
+                # x: TextChannel = commands.CurrentChannel
+                # x = commands.CurrentChannel
+                # In both of these cases, the default parameter has an explicit annotation
+                # but in the second case it's only used as the fallback.
+                if default._fallback:
+                    if parameter.annotation is Parameter.empty:
+                        parameter._annotation = default.annotation
+                else:
+                    parameter._annotation = default.annotation
 
             parameter._default = default.default
             parameter._displayed_default = default._displayed_default
diff --git a/discord/ext/commands/parameters.py b/discord/ext/commands/parameters.py
index 1204dd5e3..4bc4bdeee 100644
--- a/discord/ext/commands/parameters.py
+++ b/discord/ext/commands/parameters.py
@@ -31,6 +31,16 @@ from typing import TYPE_CHECKING, Any, Literal, Optional, OrderedDict, Union
 from discord.utils import MISSING, maybe_coroutine
 
 from .errors import NoPrivateMessage
+from .converter import GuildConverter
+
+from discord import (
+    Member,
+    User,
+    TextChannel,
+    VoiceChannel,
+    DMChannel,
+    Thread,
+)
 
 if TYPE_CHECKING:
     from typing_extensions import Self
@@ -77,7 +87,7 @@ class Parameter(inspect.Parameter):
     .. versionadded:: 2.0
     """
 
-    __slots__ = ('_displayed_default',)
+    __slots__ = ('_displayed_default', '_fallback')
 
     def __init__(
         self,
@@ -93,6 +103,7 @@ class Parameter(inspect.Parameter):
         self._default = default
         self._annotation = annotation
         self._displayed_default = displayed_default
+        self._fallback = False
 
     def replace(
         self,
@@ -218,12 +229,16 @@ An alias for :func:`parameter`.
 Author = parameter(
     default=attrgetter('author'),
     displayed_default='<you>',
+    converter=Union[Member, User],
 )
+Author._fallback = True
 
 CurrentChannel = parameter(
     default=attrgetter('channel'),
     displayed_default='<this channel>',
+    converter=Union[TextChannel, DMChannel, Thread, VoiceChannel],
 )
+CurrentChannel._fallback = True
 
 
 def default_guild(ctx: Context) -> Guild:
@@ -235,6 +250,7 @@ def default_guild(ctx: Context) -> Guild:
 CurrentGuild = parameter(
     default=default_guild,
     displayed_default='<this server>',
+    converter=GuildConverter,
 )