[commands] Require number of parameters at instantiation time

This allows it to bypass annotation evaluation for arguments that don't
matter like self and context.

discord/utils.py

@@ -1061,6 +1061,21 @@ def resolve_annotation(
     return evaluate_annotation(annotation, globalns, locals, cache)
 
 
+def is_inside_class(func: Callable[..., Any]) -> bool:
+    # For methods defined in a class, the qualname has a dotted path
+    # denoting which class it belongs to. So, e.g. for A.foo the qualname
+    # would be A.foo while a global foo() would just be foo.
+    #
+    # Unfortuately, for nested functions this breaks. So inside an outer
+    # function named outer, those two would end up having a qualname with
+    # outer.<locals>.A.foo and outer.<locals>.foo
+
+    if func.__qualname__ == func.__name__:
+        return False
+    (remaining, _, _) = func.__qualname__.rpartition('.')
+    return not remaining.endswith('<locals>')
+
+
 TimestampStyle = Literal['f', 'F', 'd', 'D', 't', 'T', 'R']