gh-137814: [3.14] Fix __qualname__ of __annotate__ functions in the interpreter

I'd still like to do #137842 on 3.15+, but that requires changing bytecode and we can't
really afford to do that in 3.14. So to fix this in 3.14, let's patch things up in the
ceval loop instead.

This is safe because the compiler only sets __annotate__ to just-created dedicated
annotate functions.

Author: JelleZijlstra

Include/internal/pycore_opcode_metadata.h

@@ -836,6 +836,23 @@ def test_complex_comprehension_inlining_exec(self):
         lamb = list(genexp)[0]
         self.assertEqual(lamb(), 42)
 
+    def test_annotate_qualname(self):
+        code = """
+        def f() -> None:
+            def nested() -> None: pass
+            return nested
+        class Outer:
+            x: int
+            def method(self, x: int):
+                pass
+        """
+        ns = run_code(code)
+        method = ns["Outer"].method
+        self.assertEqual(ns["f"].__annotate__.__qualname__, "f.__annotate__")
+        self.assertEqual(ns["f"]().__annotate__.__qualname__, "f.<locals>.nested.__annotate__")
+        self.assertEqual(method.__annotate__.__qualname__, "Outer.method.__annotate__")
+        self.assertEqual(ns["Outer"].__annotate__.__qualname__, "Outer.__annotate__")
+
     # gh-138349
     def test_module_level_annotation_plus_listcomp(self):
         cases = [

Include/internal/pycore_uop_metadata.h

@@ -0,0 +1,2 @@
+Fix the ``__qualname__`` attribute of ``__annotate__`` functions on
+functions.

Lib/test/test_type_annotations.py

@@ -4970,6 +4970,13 @@ dummy_func(
             PyObject **ptr = (PyObject **)(((char *)func) + offset);
             assert(*ptr == NULL);
             *ptr = attr;
+            if (oparg == MAKE_FUNCTION_ANNOTATE && PyFunction_Check(attr)) {
+                // gh-137814: Fix the qualname of __annotate__ functions
+                PyFunctionObject *func_obj = (PyFunctionObject *)attr;
+                PyObject *fixed_qualname = PyUnicode_FromFormat("%U.__annotate__", ((PyFunctionObject *)func)->func_qualname);
+                ERROR_IF(fixed_qualname == NULL);
+                Py_SETREF(func_obj->func_qualname, fixed_qualname);
+            }
         }
 
         inst(RETURN_GENERATOR, (-- res)) {