TYP,BUG: Reduce argument validation in C-based __class_getitem__

numpy/core/src/multiarray/methods.c

@@ -2829,7 +2829,7 @@ array_class_getitem(PyObject *cls, PyObject *args)
     Py_ssize_t args_len;
 
     args_len = PyTuple_Check(args) ? PyTuple_Size(args) : 1;
-    if (args_len != 2) {
+    if ((args_len > 2) || (args_len == 0)) {
         return PyErr_Format(PyExc_TypeError,
                             "Too %s arguments for %s",
                             args_len > 2 ? "many" : "few",

numpy/core/src/multiarray/scalartypes.c.src

@@ -1855,7 +1855,7 @@ numbertype_class_getitem_abc(PyObject *cls, PyObject *args)
     }
 
     args_len = PyTuple_Check(args) ? PyTuple_Size(args) : 1;
-    if (args_len != args_len_expected) {
+    if ((args_len > args_len_expected) || (args_len == 0)) {
         return PyErr_Format(PyExc_TypeError,
                             "Too %s arguments for %s",
                             args_len > args_len_expected ? "many" : "few",

numpy/core/tests/test_arraymethod.py

@@ -3,9 +3,11 @@
 this is private API, but when added, public API may be added here.
 """
 
+from __future__ import annotations
+
 import sys
 import types
-from typing import Any, Type
+from typing import Any
 
 import pytest
 
@@ -63,28 +65,25 @@ def test_invalid_arguments(self, args, error):
 
 
 @pytest.mark.skipif(sys.version_info < (3, 9), reason="Requires python 3.9")
+@pytest.mark.parametrize(
+    "cls", [np.ndarray, np.recarray, np.chararray, np.matrix, np.memmap]
+)
 class TestClassGetItem:
-    @pytest.mark.parametrize(
-        "cls", [np.ndarray, np.recarray, np.chararray, np.matrix, np.memmap]
-    )
-    def test_class_getitem(self, cls: Type[np.ndarray]) -> None:
+    def test_class_getitem(self, cls: type[np.ndarray]) -> None:
         """Test `ndarray.__class_getitem__`."""
         alias = cls[Any, Any]
         assert isinstance(alias, types.GenericAlias)
         assert alias.__origin__ is cls
 
     @pytest.mark.parametrize("arg_len", range(4))
-    def test_subscript_tuple(self, arg_len: int) -> None:
+    def test_subscript_tup(self, cls: type[np.ndarray], arg_len: int) -> None:
         arg_tup = (Any,) * arg_len
-        if arg_len == 2:
-            assert np.ndarray[arg_tup]
+        if arg_len in (1, 2):
+            assert cls[arg_tup]
         else:
-            with pytest.raises(TypeError):
-                np.ndarray[arg_tup]
-
-    def test_subscript_scalar(self) -> None:
-        with pytest.raises(TypeError):
-            np.ndarray[Any]
+            match = f"Too {'few' if arg_len == 0 else 'many'} arguments"
+            with pytest.raises(TypeError, match=match):
+                cls[arg_tup]
 
 
 @pytest.mark.skipif(sys.version_info >= (3, 9), reason="Requires python 3.8")

numpy/core/tests/test_scalar_methods.py

@@ -153,6 +153,16 @@ def test_abc_complexfloating(self) -> None:
         assert isinstance(alias, types.GenericAlias)
         assert alias.__origin__ is np.complexfloating
 
+    @pytest.mark.parametrize("arg_len", range(4))
+    def test_abc_complexfloating_subscript_tuple(self, arg_len: int) -> None:
+        arg_tup = (Any,) * arg_len
+        if arg_len in (1, 2):
+            assert np.complexfloating[arg_tup]
+        else:
+            match = f"Too {'few' if arg_len == 0 else 'many'} arguments"
+            with pytest.raises(TypeError, match=match):
+                np.complexfloating[arg_tup]
+
     @pytest.mark.parametrize("cls", [np.generic, np.flexible, np.character])
     def test_abc_non_numeric(self, cls: Type[np.generic]) -> None:
         with pytest.raises(TypeError):