gh-107704: Argument Clinic: add support for deprecating keyword use of parameters (GH-107984)

It is now possible to deprecate passing keyword arguments for
keyword-or-positional parameters with Argument Clinic, using the new
'/ [from X.Y]' syntax.
(To be read as "positional-only from Python version X.Y")

Co-authored-by: Erlend E. Aasland <erlend@python.org>
Co-authored-by: Alex Waygood <Alex.Waygood@Gmail.com>

Doc/howto/clinic.rst

@@ -1941,54 +1941,70 @@ The generated docstring ends up looking like this:
 
 
 .. _clinic-howto-deprecate-positional:
+.. _clinic-howto-deprecate-keyword:
 
-How to deprecate passing parameters positionally
+How to deprecate passing parameters positionally or by keyword
-------------------------------------------------
+--------------------------------------------------------------
 
 Argument Clinic provides syntax that makes it possible to generate code that
-deprecates passing :term:`arguments <argument>` positionally.
+deprecates passing :term:`arguments <argument>` for positional-or-keyword
+:term:`parameters <parameter>` positionally or by keyword.
 For example, say we've got a module-level function :py:func:`!foo.myfunc`
-that has three :term:`parameters <parameter>`:
+that has five parameters: a positional-only parameter *a*, three
-positional-or-keyword parameters *a* and *b*, and a keyword-only parameter *c*::
+positional-or-keyword parameters *b*, *c* and *d*, and a keyword-only
+parameter *e*::
 
    /*[clinic input]
    module foo
    myfunc
        a: int
+       /
        b: int
-       *
        c: int
+       d: int
+       *
+       e: int
    [clinic start generated output]*/
 
-We now want to make the *b* parameter keyword-only;
+We now want to make the *b* parameter positional-only and the *d* parameter
-however, we'll have to wait two releases before making this change,
+keyword-only;
+however, we'll have to wait two releases before making these changes,
 as mandated by Python's backwards-compatibility policy (see :pep:`387`).
 For this example, imagine we're in the development phase for Python 3.12:
 that means we'll be allowed to introduce deprecation warnings in Python 3.12
-whenever the *b* parameter is passed positionally,
+whenever an argument for the *b* parameter is passed by keyword or an argument
-and we'll be allowed to make it keyword-only in Python 3.14 at the earliest.
+for the *d* parameter is passed positionally, and we'll be allowed to make
+them positional-only and keyword-only respectively in Python 3.14 at
+the earliest.
 
 We can use Argument Clinic to emit the desired deprecation warnings
-using the ``* [from ...]`` syntax,
+using the ``[from ...]`` syntax, by adding the line ``/ [from 3.14]`` right
-by adding the line ``* [from 3.14]`` right above the *b* parameter::
+below the *b* parameter and adding the line ``* [from 3.14]`` right above
+the *d* parameter::
 
    /*[clinic input]
    module foo
    myfunc
        a: int
-       * [from 3.14]
+       /
        b: int
-       *
+       / [from 3.14]
        c: int
+       * [from 3.14]
+       d: int
+       *
+       e: int
    [clinic start generated output]*/
 
 Next, regenerate Argument Clinic code (``make clinic``),
 and add unit tests for the new behaviour.
 
 The generated code will now emit a :exc:`DeprecationWarning`
-when an :term:`argument` for the :term:`parameter` *b* is passed positionally.
+when an :term:`argument` for the :term:`parameter` *d* is passed positionally
+(e.g ``myfunc(1, 2, 3, 4, e=5)``) or an argument for the parameter *b* is
+passed by keyword (e.g ``myfunc(1, b=2, c=3, d=4, e=5)``).
 C preprocessor directives are also generated for emitting
-compiler warnings if the ``* [from ...]`` line has not been removed
+compiler warnings if the ``[from ...]`` lines have not been removed
 from the Argument Clinic input when the deprecation period is over,
 which means when the alpha phase of the specified Python version kicks in.
 
@@ -2001,21 +2017,26 @@ Luckily for us, compiler warnings are now generated:
 .. code-block:: none
 
    In file included from Modules/foomodule.c:139:
-   Modules/clinic/foomodule.c.h:139:8: warning: In 'foomodule.c', update parameter(s) 'a' and 'b' in the clinic input of 'mymod.myfunc' to be keyword-only. [-W#warnings]
+   Modules/clinic/foomodule.c.h:139:8: warning: In 'foomodule.c', update the clinic input of 'mymod.myfunc'. [-W#warnings]
-    #    warning "In 'foomodule.c', update parameter(s) 'a' and 'b' in the clinic input of 'mymod.myfunc' to be keyword-only. [-W#warnings]"
+    #    warning "In 'foomodule.c', update the clinic input of 'mymod.myfunc'. [-W#warnings]"
          ^
 
-We now close the deprecation phase by making *b* keyword-only;
+We now close the deprecation phase by making *a* positional-only and *c*
-replace the ``* [from ...]`` line above *b*
+keyword-only;
-with the ``*`` from the line above *c*::
+replace the ``/ [from ...]`` line below *b* with the ``/`` from the line
+below *a* and the ``* [from ...]`` line above *d* with the ``*`` from
+the line above *e*::
 
    /*[clinic input]
    module foo
    myfunc
        a: int
-       *
        b: int
+       /
        c: int
+       *
+       d: int
+       e: int
    [clinic start generated output]*/
 
 Finally, run ``make clinic`` to regenerate the Argument Clinic code,

Lib/test/test_clinic.py

@@ -1611,7 +1611,7 @@ class ClinicParserTest(TestCase):
             "module foo\nfoo.bar\n  this: int\n  *",
             "module foo\nfoo.bar\n  this: int\n  *\nDocstring.",
         )
-        err = "Function 'foo.bar' specifies '*' without any parameters afterwards."
+        err = "Function 'bar' specifies '*' without following parameters."
         for block in dataset:
             with self.subTest(block=block):
                 self.expect_failure(block, err)
@@ -1679,7 +1679,7 @@ class ClinicParserTest(TestCase):
             Docstring.
         """
         err = (
-            "Function 'foo.bar': expected format '* [from major.minor]' "
+            "Function 'bar': expected format '[from major.minor]' "
             "where 'major' and 'minor' are integers; got '3'"
         )
         self.expect_failure(block, err, lineno=3)
@@ -1693,7 +1693,7 @@ class ClinicParserTest(TestCase):
             Docstring.
         """
         err = (
-            "Function 'foo.bar': expected format '* [from major.minor]' "
+            "Function 'bar': expected format '[from major.minor]' "
             "where 'major' and 'minor' are integers; got 'a.b'"
         )
         self.expect_failure(block, err, lineno=3)
@@ -1707,7 +1707,7 @@ class ClinicParserTest(TestCase):
             Docstring.
         """
         err = (
-            "Function 'foo.bar': expected format '* [from major.minor]' "
+            "Function 'bar': expected format '[from major.minor]' "
             "where 'major' and 'minor' are integers; got '1.2.3'"
         )
         self.expect_failure(block, err, lineno=3)
@@ -1721,8 +1721,24 @@ class ClinicParserTest(TestCase):
             Docstring.
         """
         err = (
-            "Function 'foo.bar' specifies '* [from ...]' without "
+            "Function 'bar' specifies '* [from ...]' without "
-            "any parameters afterwards"
+            "following parameters."
+        )
+        self.expect_failure(block, err, lineno=4)
+
+    def test_parameters_required_after_depr_star2(self):
+        block = """
+            module foo
+            foo.bar
+                a: int
+                * [from 3.14]
+                *
+                b: int
+            Docstring.
+        """
+        err = (
+            "Function 'bar' specifies '* [from ...]' without "
+            "following parameters."
         )
         self.expect_failure(block, err, lineno=4)
 
@@ -1735,7 +1751,7 @@ class ClinicParserTest(TestCase):
                 * [from 3.14]
             Docstring.
         """
-        err = "Function 'foo.bar': '* [from ...]' must come before '*'"
+        err = "Function 'bar': '* [from ...]' must come before '*'"
         self.expect_failure(block, err, lineno=4)
 
     def test_depr_star_duplicate(self):
@@ -1749,7 +1765,49 @@ class ClinicParserTest(TestCase):
                 c: int
             Docstring.
         """
-        err = "Function 'foo.bar' uses '[from ...]' more than once"
+        err = "Function 'bar' uses '* [from ...]' more than once."
+        self.expect_failure(block, err, lineno=5)
+
+    def test_depr_star_duplicate2(self):
+        block = """
+            module foo
+            foo.bar
+                a: int
+                * [from 3.14]
+                b: int
+                * [from 3.15]
+                c: int
+            Docstring.
+        """
+        err = "Function 'bar' uses '* [from ...]' more than once."
+        self.expect_failure(block, err, lineno=5)
+
+    def test_depr_slash_duplicate(self):
+        block = """
+            module foo
+            foo.bar
+                a: int
+                / [from 3.14]
+                b: int
+                / [from 3.14]
+                c: int
+            Docstring.
+        """
+        err = "Function 'bar' uses '/ [from ...]' more than once."
+        self.expect_failure(block, err, lineno=5)
+
+    def test_depr_slash_duplicate2(self):
+        block = """
+            module foo
+            foo.bar
+                a: int
+                / [from 3.14]
+                b: int
+                / [from 3.15]
+                c: int
+            Docstring.
+        """
+        err = "Function 'bar' uses '/ [from ...]' more than once."
         self.expect_failure(block, err, lineno=5)
 
     def test_single_slash(self):
@@ -1765,6 +1823,34 @@ class ClinicParserTest(TestCase):
         )
         self.expect_failure(block, err)
 
+    def test_parameters_required_before_depr_slash(self):
+        block = """
+            module foo
+            foo.bar
+                / [from 3.14]
+            Docstring.
+        """
+        err = (
+            "Function 'bar' specifies '/ [from ...]' without "
+            "preceding parameters."
+        )
+        self.expect_failure(block, err, lineno=2)
+
+    def test_parameters_required_before_depr_slash2(self):
+        block = """
+            module foo
+            foo.bar
+                a: int
+                /
+                / [from 3.14]
+            Docstring.
+        """
+        err = (
+            "Function 'bar' specifies '/ [from ...]' without "
+            "preceding parameters."
+        )
+        self.expect_failure(block, err, lineno=4)
+
     def test_double_slash(self):
         block = """
             module foo
@@ -1787,12 +1873,61 @@ class ClinicParserTest(TestCase):
                z: int
                /
         """
-        err = (
+        err = "Function 'bar': '/' must precede '*'"
-            "Function 'bar' mixes keyword-only and positional-only parameters, "
-            "which is unsupported."
-        )
         self.expect_failure(block, err)
 
+    def test_depr_star_must_come_after_slash(self):
+        block = """
+            module foo
+            foo.bar
+                a: int
+                * [from 3.14]
+                /
+                b: int
+            Docstring.
+        """
+        err = "Function 'bar': '/' must precede '* [from ...]'"
+        self.expect_failure(block, err, lineno=4)
+
+    def test_depr_star_must_come_after_depr_slash(self):
+        block = """
+            module foo
+            foo.bar
+                a: int
+                * [from 3.14]
+                / [from 3.14]
+                b: int
+            Docstring.
+        """
+        err = "Function 'bar': '/ [from ...]' must precede '* [from ...]'"
+        self.expect_failure(block, err, lineno=4)
+
+    def test_star_must_come_after_depr_slash(self):
+        block = """
+            module foo
+            foo.bar
+                a: int
+                *
+                / [from 3.14]
+                b: int
+            Docstring.
+        """
+        err = "Function 'bar': '/ [from ...]' must precede '*'"
+        self.expect_failure(block, err, lineno=4)
+
+    def test_depr_slash_must_come_after_slash(self):
+        block = """
+            module foo
+            foo.bar
+                a: int
+                / [from 3.14]
+                /
+                b: int
+            Docstring.
+        """
+        err = "Function 'bar': '/' must precede '/ [from ...]'"
+        self.expect_failure(block, err, lineno=4)
+
     def test_parameters_not_permitted_after_slash_for_now(self):
         block = """
             module foo
@@ -2589,11 +2724,33 @@ class ClinicFunctionalTest(unittest.TestCase):
     locals().update((name, getattr(ac_tester, name))
                     for name in dir(ac_tester) if name.startswith('test_'))
 
-    def check_depr_star(self, pnames, fn, *args, **kwds):
+    def check_depr_star(self, pnames, fn, *args, name=None, **kwds):
+        if name is None:
+            name = fn.__qualname__
+            if isinstance(fn, type):
+                name = f'{fn.__module__}.{name}'
         regex = (
             fr"Passing( more than)?( [0-9]+)? positional argument(s)? to "
-            fr"{fn.__name__}\(\) is deprecated. Parameter(s)? {pnames} will "
+            fr"{re.escape(name)}\(\) is deprecated. Parameters? {pnames} will "
-            fr"become( a)? keyword-only parameter(s)? in Python 3\.14"
+            fr"become( a)? keyword-only parameters? in Python 3\.14"
+        )
+        with self.assertWarnsRegex(DeprecationWarning, regex) as cm:
+            # Record the line number, so we're sure we've got the correct stack
+            # level on the deprecation warning.
+            _, lineno = fn(*args, **kwds), sys._getframe().f_lineno
+        self.assertEqual(cm.filename, __file__)
+        self.assertEqual(cm.lineno, lineno)
+
+    def check_depr_kwd(self, pnames, fn, *args, name=None, **kwds):
+        if name is None:
+            name = fn.__qualname__
+            if isinstance(fn, type):
+                name = f'{fn.__module__}.{name}'
+        pl = 's' if ' ' in pnames else ''
+        regex = (
+            fr"Passing keyword argument{pl} {pnames} to "
+            fr"{re.escape(name)}\(\) is deprecated. Corresponding parameter{pl} "
+            fr"will become positional-only in Python 3\.14."
         )
         with self.assertWarnsRegex(DeprecationWarning, regex) as cm:
             # Record the line number, so we're sure we've got the correct stack
@@ -3067,46 +3224,67 @@ class ClinicFunctionalTest(unittest.TestCase):
                 self.assertEqual(func(), name)
 
     def test_depr_star_new(self):
-        regex = re.escape(
+        cls = ac_tester.DeprStarNew
-            "Passing positional arguments to _testclinic.DeprStarNew() is "
+        cls()
-            "deprecated. Parameter 'a' will become a keyword-only parameter "
+        cls(a=None)
-            "in Python 3.14."
+        self.check_depr_star("'a'", cls, None)
-        )
-        with self.assertWarnsRegex(DeprecationWarning, regex) as cm:
-            ac_tester.DeprStarNew(None)
-        self.assertEqual(cm.filename, __file__)
 
     def test_depr_star_new_cloned(self):
-        regex = re.escape(
+        fn = ac_tester.DeprStarNew().cloned
-            "Passing positional arguments to _testclinic.DeprStarNew.cloned() "
+        fn()
-            "is deprecated. Parameter 'a' will become a keyword-only parameter "
+        fn(a=None)
-            "in Python 3.14."
+        self.check_depr_star("'a'", fn, None, name='_testclinic.DeprStarNew.cloned')
-        )
-        obj = ac_tester.DeprStarNew(a=None)
-        with self.assertWarnsRegex(DeprecationWarning, regex) as cm:
-            obj.cloned(None)
-        self.assertEqual(cm.filename, __file__)
 
     def test_depr_star_init(self):
-        regex = re.escape(
+        cls = ac_tester.DeprStarInit
-            "Passing positional arguments to _testclinic.DeprStarInit() is "
+        cls()
-            "deprecated. Parameter 'a' will become a keyword-only parameter "
+        cls(a=None)
-            "in Python 3.14."
+        self.check_depr_star("'a'", cls, None)
-        )
-        with self.assertWarnsRegex(DeprecationWarning, regex) as cm:
-            ac_tester.DeprStarInit(None)
-        self.assertEqual(cm.filename, __file__)
 
     def test_depr_star_init_cloned(self):
-        regex = re.escape(
+        fn = ac_tester.DeprStarInit().cloned
-            "Passing positional arguments to _testclinic.DeprStarInit.cloned() "
+        fn()
-            "is deprecated. Parameter 'a' will become a keyword-only parameter "
+        fn(a=None)
-            "in Python 3.14."
+        self.check_depr_star("'a'", fn, None, name='_testclinic.DeprStarInit.cloned')
-        )
+
-        obj = ac_tester.DeprStarInit(a=None)
+    def test_depr_star_init_noinline(self):
-        with self.assertWarnsRegex(DeprecationWarning, regex) as cm:
+        cls = ac_tester.DeprStarInitNoInline
-            obj.cloned(None)
+        self.assertRaises(TypeError, cls, "a")
-        self.assertEqual(cm.filename, __file__)
+        cls(a="a", b="b")
+        cls(a="a", b="b", c="c")
+        cls("a", b="b")
+        cls("a", b="b", c="c")
+        check = partial(self.check_depr_star, "'b' and 'c'", cls)
+        check("a", "b")
+        check("a", "b", "c")
+        check("a", "b", c="c")
+        self.assertRaises(TypeError, cls, "a", "b", "c", "d")
+
+    def test_depr_kwd_new(self):
+        cls = ac_tester.DeprKwdNew
+        cls()
+        cls(None)
+        self.check_depr_kwd("'a'", cls, a=None)
+
+    def test_depr_kwd_init(self):
+        cls = ac_tester.DeprKwdInit
+        cls()
+        cls(None)
+        self.check_depr_kwd("'a'", cls, a=None)
+
+    def test_depr_kwd_init_noinline(self):
+        cls = ac_tester.DeprKwdInitNoInline
+        cls = ac_tester.depr_star_noinline
+        self.assertRaises(TypeError, cls, "a")
+        cls(a="a", b="b")
+        cls(a="a", b="b", c="c")
+        cls("a", b="b")
+        cls("a", b="b", c="c")
+        check = partial(self.check_depr_star, "'b' and 'c'", cls)
+        check("a", "b")
+        check("a", "b", "c")
+        check("a", "b", c="c")
+        self.assertRaises(TypeError, cls, "a", "b", "c", "d")
 
     def test_depr_star_pos0_len1(self):
         fn = ac_tester.depr_star_pos0_len1
@@ -3177,6 +3355,103 @@ class ClinicFunctionalTest(unittest.TestCase):
         check("a", "b", "c", d=0, e=0)
         check("a", "b", "c", "d", e=0)
 
+    def test_depr_star_noinline(self):
+        fn = ac_tester.depr_star_noinline
+        self.assertRaises(TypeError, fn, "a")
+        fn(a="a", b="b")
+        fn(a="a", b="b", c="c")
+        fn("a", b="b")
+        fn("a", b="b", c="c")
+        check = partial(self.check_depr_star, "'b' and 'c'", fn)
+        check("a", "b")
+        check("a", "b", "c")
+        check("a", "b", c="c")
+        self.assertRaises(TypeError, fn, "a", "b", "c", "d")
+
+    def test_depr_kwd_required_1(self):
+        fn = ac_tester.depr_kwd_required_1
+        fn("a", "b")
+        self.assertRaises(TypeError, fn, "a")
+        self.assertRaises(TypeError, fn, "a", "b", "c")
+        check = partial(self.check_depr_kwd, "'b'", fn)
+        check("a", b="b")
+        self.assertRaises(TypeError, fn, a="a", b="b")
+
+    def test_depr_kwd_required_2(self):
+        fn = ac_tester.depr_kwd_required_2
+        fn("a", "b", "c")
+        self.assertRaises(TypeError, fn, "a", "b")
+        self.assertRaises(TypeError, fn, "a", "b", "c", "d")
+        check = partial(self.check_depr_kwd, "'b' and 'c'", fn)
+        check("a", "b", c="c")
+        check("a", b="b", c="c")
+        self.assertRaises(TypeError, fn, a="a", b="b", c="c")
+
+    def test_depr_kwd_optional_1(self):
+        fn = ac_tester.depr_kwd_optional_1
+        fn("a")
+        fn("a", "b")
+        self.assertRaises(TypeError, fn)
+        self.assertRaises(TypeError, fn, "a", "b", "c")
+        check = partial(self.check_depr_kwd, "'b'", fn)
+        check("a", b="b")
+        self.assertRaises(TypeError, fn, a="a", b="b")
+
+    def test_depr_kwd_optional_2(self):
+        fn = ac_tester.depr_kwd_optional_2
+        fn("a")
+        fn("a", "b")
+        fn("a", "b", "c")
+        self.assertRaises(TypeError, fn)
+        self.assertRaises(TypeError, fn, "a", "b", "c", "d")
+        check = partial(self.check_depr_kwd, "'b' and 'c'", fn)
+        check("a", b="b")
+        check("a", c="c")
+        check("a", b="b", c="c")
+        check("a", c="c", b="b")
+        check("a", "b", c="c")
+        self.assertRaises(TypeError, fn, a="a", b="b", c="c")
+
+    def test_depr_kwd_optional_3(self):
+        fn = ac_tester.depr_kwd_optional_3
+        fn()
+        fn("a")
+        fn("a", "b")
+        fn("a", "b", "c")
+        self.assertRaises(TypeError, fn, "a", "b", "c", "d")
+        check = partial(self.check_depr_kwd, "'a', 'b' and 'c'", fn)
+        check("a", "b", c="c")
+        check("a", b="b")
+        check(a="a")
+
+    def test_depr_kwd_required_optional(self):
+        fn = ac_tester.depr_kwd_required_optional
+        fn("a", "b")
+        fn("a", "b", "c")
+        self.assertRaises(TypeError, fn)
+        self.assertRaises(TypeError, fn, "a")
+        self.assertRaises(TypeError, fn, "a", "b", "c", "d")
+        check = partial(self.check_depr_kwd, "'b' and 'c'", fn)
+        check("a", b="b")
+        check("a", b="b", c="c")
+        check("a", c="c", b="b")
+        check("a", "b", c="c")
+        self.assertRaises(TypeError, fn, "a", c="c")
+        self.assertRaises(TypeError, fn, a="a", b="b", c="c")
+
+    def test_depr_kwd_noinline(self):
+        fn = ac_tester.depr_kwd_noinline
+        fn("a", "b")
+        fn("a", "b", "c")
+        self.assertRaises(TypeError, fn, "a")
+        check = partial(self.check_depr_kwd, "'b' and 'c'", fn)
+        check("a", b="b")
+        check("a", b="b", c="c")
+        check("a", c="c", b="b")
+        check("a", "b", c="c")
+        self.assertRaises(TypeError, fn, "a", c="c")
+        self.assertRaises(TypeError, fn, a="a", b="b", c="c")
+
 
 class PermutationTests(unittest.TestCase):
     """Test permutation support functions."""

Misc/NEWS.d/next/Tools-Demos/2023-08-15-19-50-49.gh-issue-107704.Uu84vd.rst

@@ -0,0 +1,4 @@
+It is now possible to deprecate passing keyword arguments for
+keyword-or-positional parameters with Argument Clinic, using the new ``/
+[from X.Y]`` syntax. (To be read as *"positional-only from Python version
+X.Y"*.) See :ref:`clinic-howto-deprecate-keyword` for more information.

Modules/_sqlite/clinic/connection.c.h

@@ -16,6 +16,17 @@ pysqlite_connection_init_impl(pysqlite_Connection *self, PyObject *database,
                               int cache_size, int uri,
                               enum autocommit_mode autocommit);
 
+// Emit compiler warnings when we get to Python 3.15.
+#if PY_VERSION_HEX >= 0x030f00C0
+#  error "Update the clinic input of '_sqlite3.Connection.__init__'."
+#elif PY_VERSION_HEX >= 0x030f00A0
+#  ifdef _MSC_VER
+#    pragma message ("Update the clinic input of '_sqlite3.Connection.__init__'.")
+#  else
+#    warning "Update the clinic input of '_sqlite3.Connection.__init__'."
+#  endif
+#endif
+
 static int
 pysqlite_connection_init(PyObject *self, PyObject *args, PyObject *kwargs)
 {
@@ -59,28 +70,6 @@ pysqlite_connection_init(PyObject *self, PyObject *args, PyObject *kwargs)
     int uri = 0;
     enum autocommit_mode autocommit = LEGACY_TRANSACTION_CONTROL;
 
-    // Emit compiler warnings when we get to Python 3.15.
-    #if PY_VERSION_HEX >= 0x030f00C0
-    #  error \
-            "In connection.c, update parameter(s) 'timeout', 'detect_types', " \
-            "'isolation_level', 'check_same_thread', 'factory', " \
-            "'cached_statements' and 'uri' in the clinic input of " \
-            "'_sqlite3.Connection.__init__' to be keyword-only."
-    #elif PY_VERSION_HEX >= 0x030f00A0
-    #  ifdef _MSC_VER
-    #    pragma message ( \
-            "In connection.c, update parameter(s) 'timeout', 'detect_types', " \
-            "'isolation_level', 'check_same_thread', 'factory', " \
-            "'cached_statements' and 'uri' in the clinic input of " \
-            "'_sqlite3.Connection.__init__' to be keyword-only.")
-    #  else
-    #    warning \
-            "In connection.c, update parameter(s) 'timeout', 'detect_types', " \
-            "'isolation_level', 'check_same_thread', 'factory', " \
-            "'cached_statements' and 'uri' in the clinic input of " \
-            "'_sqlite3.Connection.__init__' to be keyword-only."
-    #  endif
-    #endif
     if (nargs > 1 && nargs <= 8) {
         if (PyErr_WarnEx(PyExc_DeprecationWarning,
                 "Passing more than 1 positional argument to _sqlite3.Connection()"
@@ -89,7 +78,7 @@ pysqlite_connection_init(PyObject *self, PyObject *args, PyObject *kwargs)
                 "'cached_statements' and 'uri' will become keyword-only "
                 "parameters in Python 3.15.", 1))
         {
-                goto exit;
+            goto exit;
         }
     }
     fastargs = _PyArg_UnpackKeywords(_PyTuple_CAST(args)->ob_item, nargs, kwargs, NULL, &_parser, 1, 8, 0, argsbuf);
@@ -1692,4 +1681,4 @@ exit:
 #ifndef DESERIALIZE_METHODDEF
     #define DESERIALIZE_METHODDEF
 #endif /* !defined(DESERIALIZE_METHODDEF) */
-/*[clinic end generated code: output=5a05e5294ad9d2ce input=a9049054013a1b77]*/
+/*[clinic end generated code: output=0ad9d55977a51b8f input=a9049054013a1b77]*/

Modules/_testclinic.c

@@ -1195,14 +1195,14 @@ clone_with_conv_f2_impl(PyObject *module, custom_t path)
 
 /*[clinic input]
 output push
-destination deprstar new file '{dirname}/clinic/_testclinic_depr_star.c.h'
+destination deprstar new file '{dirname}/clinic/_testclinic_depr.c.h'
 output everything deprstar
 #output methoddef_ifndef buffer 1
 output docstring_prototype suppress
 output parser_prototype suppress
 output impl_definition block
 [clinic start generated code]*/
-/*[clinic end generated code: output=da39a3ee5e6b4b0d input=f88f37038e00fb0a]*/
+/*[clinic end generated code: output=da39a3ee5e6b4b0d input=32116eac48a42d34]*/
 
 
 // Mock Python version 3.8
@@ -1211,7 +1211,7 @@ output impl_definition block
 #define PY_VERSION_HEX 0x03080000
 
 
-#include "clinic/_testclinic_depr_star.c.h"
+#include "clinic/_testclinic_depr.c.h"
 
 
 /*[clinic input]
@@ -1219,13 +1219,13 @@ class _testclinic.DeprStarNew "PyObject *" "PyObject"
 @classmethod
 _testclinic.DeprStarNew.__new__ as depr_star_new
     * [from 3.14]
-    a: object
+    a: object = None
 The deprecation message should use the class name instead of __new__.
 [clinic start generated code]*/
 
 static PyObject *
 depr_star_new_impl(PyTypeObject *type, PyObject *a)
-/*[clinic end generated code: output=bdbb36244f90cf46 input=f4ae7dafbc23c378]*/
+/*[clinic end generated code: output=bdbb36244f90cf46 input=fdd640db964b4dc1]*/
 {
     return type->tp_alloc(type, 0);
 }
@@ -1260,13 +1260,13 @@ static PyTypeObject DeprStarNew = {
 class _testclinic.DeprStarInit "PyObject *" "PyObject"
 _testclinic.DeprStarInit.__init__ as depr_star_init
     * [from 3.14]
-    a: object
+    a: object = None
 The deprecation message should use the class name instead of __init__.
 [clinic start generated code]*/
 
 static int
 depr_star_init_impl(PyObject *self, PyObject *a)
-/*[clinic end generated code: output=8d27b43c286d3ecc input=659ebc748d87fa86]*/
+/*[clinic end generated code: output=8d27b43c286d3ecc input=5575b77229d5e2be]*/
 {
     return 0;
 }
@@ -1298,6 +1298,116 @@ static PyTypeObject DeprStarInit = {
 };
 
 
+/*[clinic input]
+class _testclinic.DeprStarInitNoInline "PyObject *" "PyObject"
+_testclinic.DeprStarInitNoInline.__init__ as depr_star_init_noinline
+    a: object
+    * [from 3.14]
+    b: object
+    c: object = None
+    *
+    # Force to use _PyArg_ParseTupleAndKeywordsFast.
+    d: str(accept={str, robuffer}, zeroes=True) = ''
+[clinic start generated code]*/
+
+static int
+depr_star_init_noinline_impl(PyObject *self, PyObject *a, PyObject *b,
+                             PyObject *c, const char *d, Py_ssize_t d_length)
+/*[clinic end generated code: output=9b31fc167f1bf9f7 input=5a887543122bca48]*/
+{
+    return 0;
+}
+
+static PyTypeObject DeprStarInitNoInline = {
+    PyVarObject_HEAD_INIT(NULL, 0)
+    .tp_name = "_testclinic.DeprStarInitNoInline",
+    .tp_basicsize = sizeof(PyObject),
+    .tp_new = PyType_GenericNew,
+    .tp_init = depr_star_init_noinline,
+    .tp_flags = Py_TPFLAGS_DEFAULT,
+};
+
+
+/*[clinic input]
+class _testclinic.DeprKwdNew "PyObject *" "PyObject"
+@classmethod
+_testclinic.DeprKwdNew.__new__ as depr_kwd_new
+    a: object = None
+    / [from 3.14]
+The deprecation message should use the class name instead of __new__.
+[clinic start generated code]*/
+
+static PyObject *
+depr_kwd_new_impl(PyTypeObject *type, PyObject *a)
+/*[clinic end generated code: output=618d07afc5616149 input=6c7d13c471013c10]*/
+{
+    return type->tp_alloc(type, 0);
+}
+
+static PyTypeObject DeprKwdNew = {
+    PyVarObject_HEAD_INIT(NULL, 0)
+    .tp_name = "_testclinic.DeprKwdNew",
+    .tp_basicsize = sizeof(PyObject),
+    .tp_new = depr_kwd_new,
+    .tp_flags = Py_TPFLAGS_DEFAULT,
+};
+
+
+/*[clinic input]
+class _testclinic.DeprKwdInit "PyObject *" "PyObject"
+_testclinic.DeprKwdInit.__init__ as depr_kwd_init
+    a: object = None
+    / [from 3.14]
+The deprecation message should use the class name instead of __init__.
+[clinic start generated code]*/
+
+static int
+depr_kwd_init_impl(PyObject *self, PyObject *a)
+/*[clinic end generated code: output=6e02eb724a85d840 input=b9bf3c20f012d539]*/
+{
+    return 0;
+}
+
+static PyTypeObject DeprKwdInit = {
+    PyVarObject_HEAD_INIT(NULL, 0)
+    .tp_name = "_testclinic.DeprKwdInit",
+    .tp_basicsize = sizeof(PyObject),
+    .tp_new = PyType_GenericNew,
+    .tp_init = depr_kwd_init,
+    .tp_flags = Py_TPFLAGS_DEFAULT,
+};
+
+
+/*[clinic input]
+class _testclinic.DeprKwdInitNoInline "PyObject *" "PyObject"
+_testclinic.DeprKwdInitNoInline.__init__ as depr_kwd_init_noinline
+    a: object
+    /
+    b: object
+    c: object = None
+    / [from 3.14]
+    # Force to use _PyArg_ParseTupleAndKeywordsFast.
+    d: str(accept={str, robuffer}, zeroes=True) = ''
+[clinic start generated code]*/
+
+static int
+depr_kwd_init_noinline_impl(PyObject *self, PyObject *a, PyObject *b,
+                            PyObject *c, const char *d, Py_ssize_t d_length)
+/*[clinic end generated code: output=27759d70ddd25873 input=c19d982c8c70a930]*/
+{
+    return 0;
+}
+
+static PyTypeObject DeprKwdInitNoInline = {
+    PyVarObject_HEAD_INIT(NULL, 0)
+    .tp_name = "_testclinic.DeprKwdInitNoInline",
+    .tp_basicsize = sizeof(PyObject),
+    .tp_new = PyType_GenericNew,
+    .tp_init = depr_kwd_init_noinline,
+    .tp_flags = Py_TPFLAGS_DEFAULT,
+};
+
+
 /*[clinic input]
 depr_star_pos0_len1
     * [from 3.14]
@@ -1450,6 +1560,148 @@ depr_star_pos2_len2_with_kwd_impl(PyObject *module, PyObject *a, PyObject *b,
 }
 
 
+/*[clinic input]
+depr_star_noinline
+    a: object
+    * [from 3.14]
+    b: object
+    c: object = None
+    *
+    # Force to use _PyArg_ParseStackAndKeywords.
+    d: str(accept={str, robuffer}, zeroes=True) = ''
+[clinic start generated code]*/
+
+static PyObject *
+depr_star_noinline_impl(PyObject *module, PyObject *a, PyObject *b,
+                        PyObject *c, const char *d, Py_ssize_t d_length)
+/*[clinic end generated code: output=cc27dacf5c2754af input=d36cc862a2daef98]*/
+{
+    Py_RETURN_NONE;
+}
+
+
+/*[clinic input]
+depr_kwd_required_1
+    a: object
+    /
+    b: object
+    / [from 3.14]
+[clinic start generated code]*/
+
+static PyObject *
+depr_kwd_required_1_impl(PyObject *module, PyObject *a, PyObject *b)
+/*[clinic end generated code: output=1d8ab19ea78418af input=53f2c398b828462d]*/
+{
+    Py_RETURN_NONE;
+}
+
+
+/*[clinic input]
+depr_kwd_required_2
+    a: object
+    /
+    b: object
+    c: object
+    / [from 3.14]
+[clinic start generated code]*/
+
+static PyObject *
+depr_kwd_required_2_impl(PyObject *module, PyObject *a, PyObject *b,
+                         PyObject *c)
+/*[clinic end generated code: output=44a89cb82509ddde input=a2b0ef37de8a01a7]*/
+{
+    Py_RETURN_NONE;
+}
+
+
+/*[clinic input]
+depr_kwd_optional_1
+    a: object
+    /
+    b: object = None
+    / [from 3.14]
+[clinic start generated code]*/
+
+static PyObject *
+depr_kwd_optional_1_impl(PyObject *module, PyObject *a, PyObject *b)
+/*[clinic end generated code: output=a8a3d67efcc7b058 input=e416981eb78c3053]*/
+{
+    Py_RETURN_NONE;
+}
+
+
+/*[clinic input]
+depr_kwd_optional_2
+    a: object
+    /
+    b: object = None
+    c: object = None
+    / [from 3.14]
+[clinic start generated code]*/
+
+static PyObject *
+depr_kwd_optional_2_impl(PyObject *module, PyObject *a, PyObject *b,
+                         PyObject *c)
+/*[clinic end generated code: output=aa2d967f26fdb9f6 input=cae3afb783bfc855]*/
+{
+    Py_RETURN_NONE;
+}
+
+
+/*[clinic input]
+depr_kwd_optional_3
+    a: object = None
+    b: object = None
+    c: object = None
+    / [from 3.14]
+[clinic start generated code]*/
+
+static PyObject *
+depr_kwd_optional_3_impl(PyObject *module, PyObject *a, PyObject *b,
+                         PyObject *c)
+/*[clinic end generated code: output=a26025bf6118fd07 input=c9183b2f9ccaf992]*/
+{
+    Py_RETURN_NONE;
+}
+
+
+/*[clinic input]
+depr_kwd_required_optional
+    a: object
+    /
+    b: object
+    c: object = None
+    / [from 3.14]
+[clinic start generated code]*/
+
+static PyObject *
+depr_kwd_required_optional_impl(PyObject *module, PyObject *a, PyObject *b,
+                                PyObject *c)
+/*[clinic end generated code: output=e53a8b7a250d8ffc input=23237a046f8388f5]*/
+{
+    Py_RETURN_NONE;
+}
+
+
+/*[clinic input]
+depr_kwd_noinline
+    a: object
+    /
+    b: object
+    c: object = None
+    / [from 3.14]
+    # Force to use _PyArg_ParseStackAndKeywords.
+    d: str(accept={str, robuffer}, zeroes=True) = ''
+[clinic start generated code]*/
+
+static PyObject *
+depr_kwd_noinline_impl(PyObject *module, PyObject *a, PyObject *b,
+                       PyObject *c, const char *d, Py_ssize_t d_length)
+/*[clinic end generated code: output=f59da8113f2bad7c input=1d6db65bebb069d7]*/
+{
+    Py_RETURN_NONE;
+}
+
 // Reset PY_VERSION_HEX
 #undef PY_VERSION_HEX
 #define PY_VERSION_HEX _SAVED_PY_VERSION
@@ -1526,6 +1778,14 @@ static PyMethodDef tester_methods[] = {
     DEPR_STAR_POS2_LEN1_METHODDEF
     DEPR_STAR_POS2_LEN2_METHODDEF
     DEPR_STAR_POS2_LEN2_WITH_KWD_METHODDEF
+    DEPR_STAR_NOINLINE_METHODDEF
+    DEPR_KWD_REQUIRED_1_METHODDEF
+    DEPR_KWD_REQUIRED_2_METHODDEF
+    DEPR_KWD_OPTIONAL_1_METHODDEF
+    DEPR_KWD_OPTIONAL_2_METHODDEF
+    DEPR_KWD_OPTIONAL_3_METHODDEF
+    DEPR_KWD_REQUIRED_OPTIONAL_METHODDEF
+    DEPR_KWD_NOINLINE_METHODDEF
     {NULL, NULL}
 };
 
@@ -1549,6 +1809,18 @@ PyInit__testclinic(void)
     if (PyModule_AddType(m, &DeprStarInit) < 0) {
         goto error;
     }
+    if (PyModule_AddType(m, &DeprStarInitNoInline) < 0) {
+        goto error;
+    }
+    if (PyModule_AddType(m, &DeprKwdNew) < 0) {
+        goto error;
+    }
+    if (PyModule_AddType(m, &DeprKwdInit) < 0) {
+        goto error;
+    }
+    if (PyModule_AddType(m, &DeprKwdInitNoInline) < 0) {
+        goto error;
+    }
     return m;
 
 error:

Tools/c-analyzer/cpython/globals-to-fix.tsv

@@ -323,7 +323,11 @@ Modules/_testcapi/vectorcall.c	-	MethodDescriptorDerived_Type	-
 Modules/_testcapi/vectorcall.c	-	MethodDescriptorNopGet_Type	-
 Modules/_testcapi/vectorcall.c	-	MethodDescriptor2_Type	-
 Modules/_testclinic.c	-	DeprStarInit	-
+Modules/_testclinic.c	-	DeprStarInitNoInline	-
 Modules/_testclinic.c	-	DeprStarNew	-
+Modules/_testclinic.c	-	DeprKwdInit	-
+Modules/_testclinic.c	-	DeprKwdInitNoInline	-
+Modules/_testclinic.c	-	DeprKwdNew	-
 
 
 ##################################

Tools/clinic/clinic.py

@@ -849,25 +849,24 @@ class CLanguage(Language):
             #define {methoddef_name}
         #endif /* !defined({methoddef_name}) */
     """)
-    DEPRECATED_POSITIONAL_PROTOTYPE: Final[str] = r"""
+    COMPILER_DEPRECATION_WARNING_PROTOTYPE: Final[str] = r"""
         // Emit compiler warnings when we get to Python {major}.{minor}.
         #if PY_VERSION_HEX >= 0x{major:02x}{minor:02x}00C0
-        #  error \
+        #  error {message}
-                {cpp_message}
         #elif PY_VERSION_HEX >= 0x{major:02x}{minor:02x}00A0
         #  ifdef _MSC_VER
-        #    pragma message ( \
+        #    pragma message ({message})
-                {cpp_message})
         #  else
-        #    warning \
+        #    warning {message}
-                {cpp_message}
         #  endif
         #endif
-        if ({condition}) {{{{
+    """
+    DEPRECATION_WARNING_PROTOTYPE: Final[str] = r"""
+        if ({condition}) {{{{{errcheck}
             if (PyErr_WarnEx(PyExc_DeprecationWarning,
-                    {depr_message}, 1))
+                    {message}, 1))
             {{{{
-                    goto exit;
+                goto exit;
             }}}}
         }}}}
     """
@@ -893,6 +892,30 @@ class CLanguage(Language):
                 function = o
         return self.render_function(clinic, function)
 
+    def compiler_deprecated_warning(
+            self,
+            func: Function,
+            parameters: list[Parameter],
+    ) -> str | None:
+        minversion: VersionTuple | None = None
+        for p in parameters:
+            for version in p.deprecated_positional, p.deprecated_keyword:
+                if version and (not minversion or minversion > version):
+                    minversion = version
+        if not minversion:
+            return None
+
+        # Format the preprocessor warning and error messages.
+        assert isinstance(self.cpp.filename, str)
+        source = os.path.basename(self.cpp.filename)
+        message = f"Update the clinic input of {func.full_name!r}."
+        code = self.COMPILER_DEPRECATION_WARNING_PROTOTYPE.format(
+            major=minversion[0],
+            minor=minversion[1],
+            message=c_repr(message),
+        )
+        return normalize_snippet(code)
+
     def deprecate_positional_use(
             self,
             func: Function,
@@ -910,15 +933,7 @@ class CLanguage(Language):
         assert first_param.deprecated_positional == last_param.deprecated_positional
         thenceforth = first_param.deprecated_positional
         assert thenceforth is not None
-
-        # Format the preprocessor warning and error messages.
-        assert isinstance(self.cpp.filename, str)
-        source = os.path.basename(self.cpp.filename)
         major, minor = thenceforth
-        cpp_message = (
-            f"In {source}, update parameter(s) {pstr} in the clinic "
-            f"input of {func.full_name!r} to be keyword-only."
-        )
 
         # Format the deprecation message.
         if first_pos == 0:
@@ -927,7 +942,7 @@ class CLanguage(Language):
             condition = f"nargs == {first_pos+1}"
             if first_pos:
                 preamble = f"Passing {first_pos+1} positional arguments to "
-            depr_message = preamble + (
+            message = preamble + (
                 f"{func.fulldisplayname}() is deprecated. Parameter {pstr} will "
                 f"become a keyword-only parameter in Python {major}.{minor}."
             )
@@ -938,26 +953,93 @@ class CLanguage(Language):
                     f"Passing more than {first_pos} positional "
                     f"argument{'s' if first_pos != 1 else ''} to "
                 )
-            depr_message = preamble + (
+            message = preamble + (
                 f"{func.fulldisplayname}() is deprecated. Parameters {pstr} will "
                 f"become keyword-only parameters in Python {major}.{minor}."
             )
 
         # Append deprecation warning to docstring.
-        lines = textwrap.wrap(f"Note: {depr_message}")
+        docstring = textwrap.fill(f"Note: {message}")
-        docstring = "\n".join(lines)
         func.docstring += f"\n\n{docstring}\n"
-
         # Format and return the code block.
-        code = self.DEPRECATED_POSITIONAL_PROTOTYPE.format(
+        code = self.DEPRECATION_WARNING_PROTOTYPE.format(
             condition=condition,
-            major=major,
+            errcheck="",
-            minor=minor,
+            message=wrapped_c_string_literal(message, width=64,
-            cpp_message=wrapped_c_string_literal(cpp_message, suffix=" \\",
+                                             subsequent_indent=20),
-                                                 width=64,
+        )
-                                                 subsequent_indent=16),
+        return normalize_snippet(code, indent=4)
-            depr_message=wrapped_c_string_literal(depr_message, width=64,
+
-                                                  subsequent_indent=20),
+    def deprecate_keyword_use(
+            self,
+            func: Function,
+            params: dict[int, Parameter],
+            argname_fmt: str | None,
+    ) -> str:
+        assert len(params) > 0
+        names = [repr(p.name) for p in params.values()]
+        first_param = next(iter(params.values()))
+        last_param = next(reversed(params.values()))
+
+        # Pretty-print list of names.
+        pstr = pprint_words(names)
+
+        # For now, assume there's only one deprecation level.
+        assert first_param.deprecated_keyword == last_param.deprecated_keyword
+        thenceforth = first_param.deprecated_keyword
+        assert thenceforth is not None
+        major, minor = thenceforth
+
+        # Format the deprecation message.
+        containscheck = ""
+        conditions = []
+        for i, p in params.items():
+            if p.is_optional():
+                if argname_fmt:
+                    conditions.append(f"nargs < {i+1} && {argname_fmt % i}")
+                elif func.kind.new_or_init:
+                    conditions.append(f"nargs < {i+1} && PyDict_Contains(kwargs, &_Py_ID({p.name}))")
+                    containscheck = "PyDict_Contains"
+                else:
+                    conditions.append(f"nargs < {i+1} && PySequence_Contains(kwnames, &_Py_ID({p.name}))")
+                    containscheck = "PySequence_Contains"
+            else:
+                conditions = [f"nargs < {i+1}"]
+        condition = ") || (".join(conditions)
+        if len(conditions) > 1:
+            condition = f"(({condition}))"
+        if last_param.is_optional():
+            if func.kind.new_or_init:
+                condition = f"kwargs && PyDict_GET_SIZE(kwargs) && {condition}"
+            else:
+                condition = f"kwnames && PyTuple_GET_SIZE(kwnames) && {condition}"
+        if len(params) == 1:
+            what1 = "argument"
+            what2 = "parameter"
+        else:
+            what1 = "arguments"
+            what2 = "parameters"
+        message = (
+            f"Passing keyword {what1} {pstr} to {func.fulldisplayname}() is deprecated. "
+            f"Corresponding {what2} will become positional-only in Python {major}.{minor}."
+        )
+        if containscheck:
+            errcheck = f"""
+            if (PyErr_Occurred()) {{{{ // {containscheck}() above can fail
+                goto exit;
+            }}}}"""
+        else:
+            errcheck = ""
+        if argname_fmt:
+            # Append deprecation warning to docstring.
+            docstring = textwrap.fill(f"Note: {message}")
+            func.docstring += f"\n\n{docstring}\n"
+        # Format and return the code block.
+        code = self.DEPRECATION_WARNING_PROTOTYPE.format(
+            condition=condition,
+            errcheck=errcheck,
+            message=wrapped_c_string_literal(message, width=64,
+                                             subsequent_indent=20),
         )
         return normalize_snippet(code, indent=4)
 
@@ -1258,6 +1340,14 @@ class CLanguage(Language):
             parser_definition = parser_body(parser_prototype, *parser_code)
 
         else:
+            deprecated_positionals: dict[int, Parameter] = {}
+            deprecated_keywords: dict[int, Parameter] = {}
+            for i, p in enumerate(parameters):
+                if p.deprecated_positional:
+                    deprecated_positionals[i] = p
+                if p.deprecated_keyword:
+                    deprecated_keywords[i] = p
+
             has_optional_kw = (max(pos_only, min_pos) + min_kw_only < len(converters) - int(vararg != NO_VARARG))
             if vararg == NO_VARARG:
                 args_declaration = "_PyArg_UnpackKeywords", "%s, %s, %s" % (
@@ -1310,7 +1400,10 @@ class CLanguage(Language):
                 flags = 'METH_METHOD|' + flags
                 parser_prototype = self.PARSER_PROTOTYPE_DEF_CLASS
 
-            deprecated_positionals: dict[int, Parameter] = {}
+            if deprecated_keywords:
+                code = self.deprecate_keyword_use(f, deprecated_keywords, argname_fmt)
+                parser_code.append(code)
+
             add_label: str | None = None
             for i, p in enumerate(parameters):
                 if isinstance(p.converter, defining_class_converter):
@@ -1325,8 +1418,6 @@ class CLanguage(Language):
                     parser_code.append("%s:" % add_label)
                     add_label = None
                 if not p.is_optional():
-                    if p.deprecated_positional:
-                        deprecated_positionals[i] = p
                     parser_code.append(normalize_snippet(parsearg, indent=4))
                 elif i < pos_only:
                     add_label = 'skip_optional_posonly'
@@ -1356,8 +1447,6 @@ class CLanguage(Language):
                                 goto %s;
                             }}
                             """ % add_label, indent=4))
-                    if p.deprecated_positional:
-                        deprecated_positionals[i] = p
                     if i + 1 == len(parameters):
                         parser_code.append(normalize_snippet(parsearg, indent=4))
                     else:
@@ -1373,12 +1462,6 @@ class CLanguage(Language):
                             }}
                             """ % add_label, indent=4))
 
-            if deprecated_positionals:
-                code = self.deprecate_positional_use(f, deprecated_positionals)
-                assert parser_code is not None
-                # Insert the deprecation code before parameter parsing.
-                parser_code.insert(0, code)
-
             if parser_code is not None:
                 if add_label:
                     parser_code.append("%s:" % add_label)
@@ -1398,6 +1481,17 @@ class CLanguage(Language):
                             goto exit;
                         }}
                         """, indent=4)]
+                    if deprecated_positionals or deprecated_keywords:
+                        declarations += "\nPy_ssize_t nargs = PyTuple_GET_SIZE(args);"
+                if deprecated_keywords:
+                    code = self.deprecate_keyword_use(f, deprecated_keywords, None)
+                    parser_code.append(code)
+
+            if deprecated_positionals:
+                code = self.deprecate_positional_use(f, deprecated_positionals)
+                # Insert the deprecation code before parameter parsing.
+                parser_code.insert(0, code)
+
             parser_definition = parser_body(parser_prototype, *parser_code,
                                             declarations=declarations)
 
@@ -1478,6 +1572,10 @@ class CLanguage(Language):
 
         parser_definition = parser_definition.replace("{return_value_declaration}", return_value_declaration)
 
+        compiler_warning = self.compiler_deprecated_warning(f, parameters)
+        if compiler_warning:
+            parser_definition = compiler_warning + "\n\n" + parser_definition
+
         d = {
             "docstring_prototype" : docstring_prototype,
             "docstring_definition" : docstring_definition,
@@ -2739,6 +2837,7 @@ class Parameter:
     group: int = 0
     # (`None` signifies that there is no deprecation)
     deprecated_positional: VersionTuple | None = None
+    deprecated_keyword: VersionTuple | None = None
     right_bracket_count: int = dc.field(init=False, default=0)
 
     def __repr__(self) -> str:
@@ -4576,6 +4675,7 @@ class DSLParser:
     keyword_only: bool
     positional_only: bool
     deprecated_positional: VersionTuple | None
+    deprecated_keyword: VersionTuple | None
     group: int
     parameter_state: ParamState
     indent: IndentStack
@@ -4583,11 +4683,7 @@ class DSLParser:
     coexist: bool
     parameter_continuation: str
     preserve_output: bool
-    star_from_version_re = create_regex(
+    from_version_re = re.compile(r'([*/]) +\[from +(.+)\]')
-        before="* [from ",
-        after="]",
-        word=False,
-    )
 
     def __init__(self, clinic: Clinic) -> None:
         self.clinic = clinic
@@ -4612,6 +4708,7 @@ class DSLParser:
         self.keyword_only = False
         self.positional_only = False
         self.deprecated_positional = None
+        self.deprecated_keyword = None
         self.group = 0
         self.parameter_state: ParamState = ParamState.START
         self.indent = IndentStack()
@@ -5089,21 +5186,22 @@ class DSLParser:
             return
 
         line = line.lstrip()
-        match = self.star_from_version_re.match(line)
+        version: VersionTuple | None = None
+        match = self.from_version_re.fullmatch(line)
         if match:
-            self.parse_deprecated_positional(match.group(1))
+            line = match[1]
-            return
+            version = self.parse_version(match[2])
 
         func = self.function
         match line:
             case '*':
-                self.parse_star(func)
+                self.parse_star(func, version)
             case '[':
                 self.parse_opening_square_bracket(func)
             case ']':
                 self.parse_closing_square_bracket(func)
             case '/':
-                self.parse_slash(func)
+                self.parse_slash(func, version)
             case param:
                 self.parse_parameter(param)
 
@@ -5404,29 +5502,36 @@ class DSLParser:
                     "Annotations must be either a name, a function call, or a string."
                 )
 
-    def parse_deprecated_positional(self, thenceforth: str) -> None:
+    def parse_version(self, thenceforth: str) -> VersionTuple:
+        """Parse Python version in `[from ...]` marker."""
         assert isinstance(self.function, Function)
-        fname = self.function.full_name
 
-        if self.keyword_only:
-            fail(f"Function {fname!r}: '* [from ...]' must come before '*'")
-        if self.deprecated_positional:
-            fail(f"Function {fname!r} uses '[from ...]' more than once.")
         try:
             major, minor = thenceforth.split(".")
-            self.deprecated_positional = int(major), int(minor)
+            return int(major), int(minor)
         except ValueError:
             fail(
-                f"Function {fname!r}: expected format '* [from major.minor]' "
+                f"Function {self.function.name!r}: expected format '[from major.minor]' "
                 f"where 'major' and 'minor' are integers; got {thenceforth!r}"
             )
 
-    def parse_star(self, function: Function) -> None:
+    def parse_star(self, function: Function, version: VersionTuple | None) -> None:
-        """Parse keyword-only parameter marker '*'."""
+        """Parse keyword-only parameter marker '*'.
-        if self.keyword_only:
+
-            fail(f"Function {function.name!r} uses '*' more than once.")
+        The 'version' parameter signifies the future version from which
-        self.deprecated_positional = None
+        the marker will take effect (None means it is already in effect).
-        self.keyword_only = True
+        """
+        if version is None:
+            if self.keyword_only:
+                fail(f"Function {function.name!r} uses '*' more than once.")
+            self.check_remaining_star()
+            self.keyword_only = True
+        else:
+            if self.keyword_only:
+                fail(f"Function {function.name!r}: '* [from ...]' must come before '*'")
+            if self.deprecated_positional:
+                fail(f"Function {function.name!r} uses '* [from ...]' more than once.")
+        self.deprecated_positional = version
 
     def parse_opening_square_bracket(self, function: Function) -> None:
         """Parse opening parameter group symbol '['."""
@@ -5460,11 +5565,38 @@ class DSLParser:
                      f"has an unsupported group configuration. "
                      f"(Unexpected state {st}.c)")
 
-    def parse_slash(self, function: Function) -> None:
+    def parse_slash(self, function: Function, version: VersionTuple | None) -> None:
-        """Parse positional-only parameter marker '/'."""
+        """Parse positional-only parameter marker '/'.
-        if self.positional_only:
+
-            fail(f"Function {function.name!r} uses '/' more than once.")
+        The 'version' parameter signifies the future version from which
+        the marker will take effect (None means it is already in effect).
+        """
+        if version is None:
+            if self.deprecated_keyword:
+                fail(f"Function {function.name!r}: '/' must precede '/ [from ...]'")
+            if self.deprecated_positional:
+                fail(f"Function {function.name!r}: '/' must precede '* [from ...]'")
+            if self.keyword_only:
+                fail(f"Function {function.name!r}: '/' must precede '*'")
+            if self.positional_only:
+                fail(f"Function {function.name!r} uses '/' more than once.")
+        else:
+            if self.deprecated_keyword:
+                fail(f"Function {function.name!r} uses '/ [from ...]' more than once.")
+            if self.deprecated_positional:
+                fail(f"Function {function.name!r}: '/ [from ...]' must precede '* [from ...]'")
+            if self.keyword_only:
+                fail(f"Function {function.name!r}: '/ [from ...]' must precede '*'")
         self.positional_only = True
+        self.deprecated_keyword = version
+        if version is not None:
+            found = False
+            for p in reversed(function.parameters.values()):
+                found = p.kind is inspect.Parameter.POSITIONAL_OR_KEYWORD
+                break
+            if not found:
+                fail(f"Function {function.name!r} specifies '/ [from ...]' "
+                     f"without preceding parameters.")
         # REQUIRED and OPTIONAL are allowed here, that allows positional-only
         # without option groups to work (and have default values!)
         allowed = {
@@ -5476,19 +5608,13 @@ class DSLParser:
         if (self.parameter_state not in allowed) or self.group:
             fail(f"Function {function.name!r} has an unsupported group configuration. "
                  f"(Unexpected state {self.parameter_state}.d)")
-        if self.keyword_only:
-            fail(f"Function {function.name!r} mixes keyword-only and "
-                 "positional-only parameters, which is unsupported.")
         # fixup preceding parameters
         for p in function.parameters.values():
-            if p.is_vararg():
+            if p.kind is inspect.Parameter.POSITIONAL_OR_KEYWORD:
-                continue
+                if version is None:
-            if (p.kind is not inspect.Parameter.POSITIONAL_OR_KEYWORD and
+                    p.kind = inspect.Parameter.POSITIONAL_ONLY
-                not isinstance(p.converter, self_converter)
+                else:
-            ):
+                    p.deprecated_keyword = version
-                fail(f"Function {function.name!r} mixes keyword-only and "
-                     "positional-only parameters, which is unsupported.")
-            p.kind = inspect.Parameter.POSITIONAL_ONLY
 
     def state_parameter_docstring_start(self, line: str) -> None:
         assert self.indent.margin is not None, "self.margin.infer() has not yet been called to set the margin"
@@ -5773,6 +5899,29 @@ class DSLParser:
                              signature=signature,
                              parameters=parameters).rstrip()
 
+    def check_remaining_star(self, lineno: int | None = None) -> None:
+        assert isinstance(self.function, Function)
+
+        if self.keyword_only:
+            symbol = '*'
+        elif self.deprecated_positional:
+            symbol = '* [from ...]'
+        else:
+            return
+
+        no_param_after_symbol = True
+        for p in reversed(self.function.parameters.values()):
+            if self.keyword_only:
+                if p.kind == inspect.Parameter.KEYWORD_ONLY:
+                    return
+            elif self.deprecated_positional:
+                if p.deprecated_positional == self.deprecated_positional:
+                    return
+            break
+
+        fail(f"Function {self.function.name!r} specifies {symbol!r} "
+             f"without following parameters.", line_number=lineno)
+
     def do_post_block_processing_cleanup(self, lineno: int) -> None:
         """
         Called when processing the block is done.
@@ -5780,28 +5929,7 @@ class DSLParser:
         if not self.function:
             return
 
-        def check_remaining(
+        self.check_remaining_star(lineno)
-                symbol: str,
-                condition: Callable[[Parameter], bool]
-        ) -> None:
-            assert isinstance(self.function, Function)
-
-            if values := self.function.parameters.values():
-                last_param = next(reversed(values))
-                no_param_after_symbol = condition(last_param)
-            else:
-                no_param_after_symbol = True
-            if no_param_after_symbol:
-                fname = self.function.full_name
-                fail(f"Function {fname!r} specifies {symbol!r} "
-                     "without any parameters afterwards.", line_number=lineno)
-
-        if self.keyword_only:
-            check_remaining("*", lambda p: p.kind != inspect.Parameter.KEYWORD_ONLY)
-
-        if self.deprecated_positional:
-            check_remaining("* [from ...]", lambda p: not p.deprecated_positional)
-
         self.function.docstring = self.format_docstring()