fix: same fix applied to group

src/click/core.py

@@ -1857,6 +1857,16 @@ def decorator(f: t.Callable[..., t.Any]) -> Command:
 
         return decorator
 
+    @t.overload
+    def group(self, __func: t.Callable[..., t.Any]) -> "Group":
+        ...
+
+    @t.overload
+    def group(
+        self, *args: t.Any, **kwargs: t.Any
+    ) -> t.Callable[[t.Callable[..., t.Any]], "Group"]:
+        ...
+
     def group(
         self, *args: t.Any, **kwargs: t.Any
     ) -> t.Union[t.Callable[[t.Callable[..., t.Any]], "Group"], "Group"]:
@@ -1879,8 +1889,10 @@ def group(
         func: t.Optional[t.Callable] = None
 
         if args and callable(args[0]):
+            assert len(args) == 1, "Please use group(...)(callable) instead"
+            assert not kwargs, "Please use group(...)(callable) instead"
             func = args[0]
-            args = args[1:]
+            args = ()
 
         if self.group_class is not None and kwargs.get("cls") is None:
             if self.group_class is type:

src/click/decorators.py

@@ -228,17 +228,16 @@ def decorator(f: t.Callable[..., t.Any]) -> Command:
 
 @t.overload
 def group(
-    name: t.Optional[str] = None,
-    **attrs: t.Any,
-) -> t.Callable[[F], Group]:
+    __name: t.Callable,
+) -> Group:
     ...
 
 
 @t.overload
 def group(
-    name: t.Callable,
+    name: t.Optional[str] = None,
     **attrs: t.Any,
-) -> Group:
+) -> t.Callable[[F], Group]:
     ...