Optimize argnames() (#2215)

Arguments cannot be parenthesized in Python 3.

The unit test for this was already removed in
8ae94aa.

astroid/nodes/scoped_nodes/scoped_nodes.py

@@ -954,7 +954,7 @@ def argnames(self) -> list[str]:
         :rtype: list(str)
         """
         if self.args.arguments:  # maybe None with builtin functions
-            names = _rec_get_names(self.args.arguments)
+            names = [elt.name for elt in self.args.arguments]
         else:
             names = []
         if self.args.vararg:
@@ -1246,7 +1246,7 @@ def argnames(self) -> list[str]:
         :rtype: list(str)
         """
         if self.args.arguments:  # maybe None with builtin functions
-            names = _rec_get_names(self.args.arguments)
+            names = [elt.name for elt in self.args.arguments]
         else:
             names = []
         if self.args.vararg:
@@ -1654,18 +1654,6 @@ async def func(things):
     """
 
 
-def _rec_get_names(args, names: list[str] | None = None) -> list[str]:
-    """return a list of all argument names"""
-    if names is None:
-        names = []
-    for arg in args:
-        if isinstance(arg, node_classes.Tuple):
-            _rec_get_names(arg.elts, names)
-        else:
-            names.append(arg.name)
-    return names
-
-
 def _is_metaclass(klass, seen=None, context: InferenceContext | None = None) -> bool:
     """Return if the given class can be
     used as a metaclass.

tests/test_scoped_nodes.py

@@ -529,6 +529,10 @@ def test_argnames(self) -> None:
             astroid["f"].argnames(), ["a", "b", "args", "c", "d", "kwargs"]
         )
 
+    def test_argnames_lambda(self) -> None:
+        lambda_node = extract_node("lambda a, b, c, *args, **kwargs: ...")
+        self.assertEqual(lambda_node.argnames(), ["a", "b", "c", "args", "kwargs"])
+
     def test_positional_only_argnames(self) -> None:
         code = "def f(a, b, /, c=None, *args, d, **kwargs): pass"
         astroid = builder.parse(code, __name__)