[3.15] gh-156466: fix cleanup on error in codegen_setup_annotations_scope (#156473) (GH-156498)

(cherry picked from commit 24e5a55)

Author: iritkatriel

Python/codegen.c

@@ -709,16 +709,8 @@ codegen_enter_scope(compiler *c, identifier name, int scope_type,
 }
 
 static int
-codegen_setup_annotations_scope(compiler *c, location loc,
-                                void *key, PyObject *name)
+codegen_emit_annotations_prologue(compiler *c, location loc)
 {
-    _PyCompile_CodeUnitMetadata umd = {
-        .u_posonlyargcount = 1,
-    };
-    RETURN_IF_ERROR(
-        codegen_enter_scope(c, name, COMPILE_SCOPE_ANNOTATIONS,
-                            key, loc.lineno, NULL, &umd));
-
     // if .format > VALUE_WITH_FAKE_GLOBALS: raise NotImplementedError
     PyObject *value_with_fake_globals = PyLong_FromLong(_Py_ANNOTATE_FORMAT_VALUE_WITH_FAKE_GLOBALS);
     if (value_with_fake_globals == NULL) {
@@ -738,6 +730,21 @@ codegen_setup_annotations_scope(compiler *c, location loc,
     return SUCCESS;
 }
 
+static int
+codegen_setup_annotations_scope(compiler *c, location loc,
+                                void *key, PyObject *name)
+{
+    _PyCompile_CodeUnitMetadata umd = {
+        .u_posonlyargcount = 1,
+    };
+    RETURN_IF_ERROR(
+        codegen_enter_scope(c, name, COMPILE_SCOPE_ANNOTATIONS,
+                            key, loc.lineno, NULL, &umd));
+
+    RETURN_IF_ERROR_IN_SCOPE(c, codegen_emit_annotations_prologue(c, loc));
+    return SUCCESS;
+}
+
 static int
 codegen_leave_annotations_scope(compiler *c, location loc)
 {