pythongh-117613: Argument Clinic: disallow defining class parameter at module level (python#117950)

Author: neonene

Lib/test/test_clinic.py

@@ -2518,6 +2518,15 @@ class m.C "PyObject *" ""
         p = function.parameters['cls']
         self.assertEqual(p.kind, inspect.Parameter.POSITIONAL_ONLY)
 
+    def test_disallow_defining_class_at_module_level(self):
+        err = "A 'defining_class' parameter cannot be defined at module level."
+        block = """
+            module m
+            m.func
+                cls: defining_class
+        """
+        self.expect_failure(block, err, lineno=2)
+
 
 class ClinicExternalTest(TestCase):
     maxDiff = None

Tools/clinic/libclinic/dsl_parser.py

@@ -1102,6 +1102,8 @@ def bad_node(self, node: ast.AST) -> None:
                     fail("A 'defining_class' parameter cannot have a default value.")
                 if self.group:
                     fail("A 'defining_class' parameter cannot be in an optional group.")
+                if self.function.cls is None:
+                    fail("A 'defining_class' parameter cannot be defined at module level.")
                 kind = inspect.Parameter.POSITIONAL_ONLY
             else:
                 fail("A 'defining_class' parameter, if specified, must either "