port: advance VC6 typeobject frontier and preserve regression coverage

scripts/vc6-setobject-frozenset-vectorcall-c89.test.py

@@ -0,0 +1,39 @@
+#!/usr/bin/env python3
+"""Check frozenset_vectorcall's C89 declarations and evaluation order."""
+import re
+import sys
+from pathlib import Path
+
+source = Path(sys.argv[1]).read_text()
+match = re.search(
+    r"static PyObject \*\nfrozenset_vectorcall\(PyObject \*type, PyObject \* const\*args,"
+    r"\s*size_t nargsf, PyObject \*kwnames\)\n\{(.*?)\n\}",
+    source,
+    re.S,
+)
+assert match, "frozenset_vectorcall not found"
+body = match.group(1)
+assert re.match(r"\s*Py_ssize_t nargs;\s*PyObject \*iterable;", body), (
+    "nargs and iterable must be declared without initializers in the initial block"
+)
+expected = """
+    Py_ssize_t nargs;
+    PyObject *iterable;
+
+    if (!_PyArg_NoKwnames("frozenset", kwnames)) {
+        return NULL;
+    }
+
+    nargs = PyVectorcall_NARGS(nargsf);
+    if (!_PyArg_CheckPositional("frozenset", nargs, 0, 1)) {
+        return NULL;
+    }
+
+    iterable = (nargs ? args[0] : NULL);
+    return make_new_frozenset(_PyType_CAST(type), iterable);
+"""
+assert re.sub(r"\s+", "", body) == re.sub(r"\s+", "", expected), (
+    "preserve keyword rejection, nargs evaluation, positional rejection, guarded "
+    "iterable evaluation, and construction in their original order"
+)
+print("frozenset_vectorcall C89 declarations and evaluation order: PASS")