gh-116171: Argument Clinic: disallow overriding return converter for __init__ methods (#116172)

Author: erlend-aasland

Lib/test/clinic.test.c

@@ -5327,47 +5327,6 @@ Test__pyarg_parsestackandkeywords_impl(TestObj *self, PyTypeObject *cls,
 /*[clinic end generated code: output=4fda8a7f2547137c input=fc72ef4b4cfafabc]*/
 
 
-/*[clinic input]
-Test.__init__ -> long
-Test overriding the __init__ return converter
-[clinic start generated code]*/
-
-PyDoc_STRVAR(Test___init____doc__,
-"Test()\n"
-"--\n"
-"\n"
-"Test overriding the __init__ return converter");
-
-static long
-Test___init___impl(TestObj *self);
-
-static int
-Test___init__(PyObject *self, PyObject *args, PyObject *kwargs)
-{
-    int return_value = -1;
-    PyTypeObject *base_tp = TestType;
-    long _return_value;
-
-    if ((Py_IS_TYPE(self, base_tp) ||
-         Py_TYPE(self)->tp_new == base_tp->tp_new) &&
-        !_PyArg_NoPositional("Test", args)) {
-        goto exit;
-    }
-    if ((Py_IS_TYPE(self, base_tp) ||
-         Py_TYPE(self)->tp_new == base_tp->tp_new) &&
-        !_PyArg_NoKeywords("Test", kwargs)) {
-        goto exit;
-    }
-    _return_value = Test___init___impl((TestObj *)self);
-    if ((_return_value == -1) && PyErr_Occurred()) {
-        goto exit;
-    }
-    return_value = PyLong_FromLong(_return_value);
-
-exit:
-    return return_value;
-}
-
 static long
 Test___init___impl(TestObj *self)
 /*[clinic end generated code: output=daf6ee12c4e443fb input=311af0dc7f17e8e9]*/

Lib/test/test_clinic.py

@@ -2146,6 +2146,14 @@ class Foo "" ""
                 expected_error = err_template.format(invalid_kind)
                 self.expect_failure(block, expected_error, lineno=3)
 
+    def test_init_cannot_define_a_return_type(self):
+        block = """
+            class Foo "" ""
+            Foo.__init__ -> long
+        """
+        expected_error = "__init__ methods cannot define a return type"
+        self.expect_failure(block, expected_error, lineno=1)
+
     def test_invalid_getset(self):
         annotations = ["@getter", "@setter"]
         for annotation in annotations:

Tools/clinic/clinic.py

@@ -5092,6 +5092,8 @@ def resolve_return_converter(
         if forced_converter:
             if self.kind in {GETTER, SETTER}:
                 fail(f"@{self.kind.name.lower()} method cannot define a return type")
+            if self.kind is METHOD_INIT:
+                fail("__init__ methods cannot define a return type")
             ast_input = f"def x() -> {forced_converter}: pass"
             try:
                 module_node = ast.parse(ast_input)