bpo-44731: Simplify the union type implementation (GH-27318) (GH-27334)

Remove direct support of typing types in the C code because they are already supported by defining methods __or__ and __ror__ in the Python code. Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>

Author: Fidget-Spinner

Lib/test/test_types.py

@@ -776,31 +776,32 @@ def test_union_parameter_chaining(self):
  self.assertEqual((list[T] | list[S])[int, int], list[int])
 
  def test_union_parameter_substitution(self):
- def eq(actual, expected):
+ def eq(actual, expected, typed=True):
  self.assertEqual(actual, expected)
- self.assertIs(type(actual), type(expected))
+ if typed:
+ self.assertIs(type(actual), type(expected))
 
  T = typing.TypeVar('T')
  S = typing.TypeVar('S')
  NT = typing.NewType('NT', str)
  x = int | T | bytes
 
- eq(x[str], int | str | bytes)
- eq(x[list[int]], int | list[int] | bytes)
+ eq(x[str], int | str | bytes, typed=False)
+ eq(x[list[int]], int | list[int] | bytes, typed=False)
  eq(x[typing.List], int | typing.List | bytes)
  eq(x[typing.List[int]], int | typing.List[int] | bytes)
  eq(x[typing.Hashable], int | typing.Hashable | bytes)
  eq(x[collections.abc.Hashable],
- int | collections.abc.Hashable | bytes)
+ int | collections.abc.Hashable | bytes, typed=False)
  eq(x[typing.Callable[[int], str]],
  int | typing.Callable[[int], str] | bytes)
  eq(x[collections.abc.Callable[[int], str]],
- int | collections.abc.Callable[[int], str] | bytes)
+ int | collections.abc.Callable[[int], str] | bytes, typed=False)
  eq(x[typing.Tuple[int, str]], int | typing.Tuple[int, str] | bytes)
  eq(x[typing.Literal['none']], int | typing.Literal['none'] | bytes)
- eq(x[str | list], int | str | list | bytes)
+ eq(x[str | list], int | str | list | bytes, typed=False)
  eq(x[typing.Union[str, list]], typing.Union[int, str, list, bytes])
- eq(x[str | int], int | str | bytes)
+ eq(x[str | int], int | str | bytes, typed=False)
  eq(x[typing.Union[str, int]], typing.Union[int, str, bytes])
  eq(x[NT], int | NT | bytes)
  eq(x[S], int | S | bytes)
@@ -829,9 +830,9 @@ def test_union_from_args(self):
  with self.assertRaisesRegex(ValueError, r"args must be not empty"):
  types.Union._from_args(())
 
- alias = types.Union._from_args((int, str, T))
+ alias = types.Union._from_args((int, list[T], None))
 
- self.assertEqual(alias.__args__, (int, str, T))
+ self.assertEqual(alias.__args__, (int, list[T], type(None)))
  self.assertEqual(alias.__parameters__, (T,))
 
  result = types.Union._from_args((int,))
@@ -894,7 +895,6 @@ def test_or_type_repr(self):
  assert repr(int | None) == "int | None"
  assert repr(int | type(None)) == "int | None"
  assert repr(int | typing.GenericAlias(list, int)) == "int | list[int]"
- assert repr(int | typing.TypeVar('T')) == "int | ~T"
 
  def test_or_type_operator_with_genericalias(self):
  a = list[int]
@@ -939,9 +939,9 @@ def __module__(self):
  TypeVar = BadMeta('TypeVar', (), {})
  _SpecialForm = BadMeta('_SpecialForm', (), {})
  # Crashes in Issue44483
- with self.assertRaises(ZeroDivisionError):
+ with self.assertRaises((TypeError, ZeroDivisionError)):
  str | TypeVar()
- with self.assertRaises(ZeroDivisionError):
+ with self.assertRaises((TypeError, ZeroDivisionError)):
  str | _SpecialForm()
 
  @cpython_only

Lib/typing.py

@@ -375,6 +375,12 @@ def __reduce__(self):
  def __call__(self, *args, **kwds):
  raise TypeError(f"Cannot instantiate {self!r}")
 
+ def __or__(self, other):
+ return Union[self, other]
+
+ def __ror__(self, other):
+ return Union[other, self]
+
  def __instancecheck__(self, obj):
  raise TypeError(f"{self} cannot be used with isinstance()")
 

Objects/unionobject.c

@@ -115,31 +115,6 @@ union_subclasscheck(PyObject *self, PyObject *instance)
  Py_RETURN_FALSE;
 }
 
-static int
-is_typing_module(PyObject *obj)
-{
- _Py_IDENTIFIER(__module__);
- PyObject *module;
- if (_PyObject_LookupAttrId(obj, &PyId___module__, &module) < 0) {
- return -1;
- }
- int is_typing = (module != NULL &&
- PyUnicode_Check(module) &&
- _PyUnicode_EqualToASCIIString(module, "typing"));
- Py_XDECREF(module);
- return is_typing;
-}
-
-static int
-is_typing_name(PyObject *obj, const char *name)
-{
- PyTypeObject *type = Py_TYPE(obj);
- if (strcmp(type->tp_name, name) != 0) {
- return 0;
- }
- return is_typing_module((PyObject *)type);
-}
-
 static PyObject *
 union_richcompare(PyObject *a, PyObject *b, int op)
 {
@@ -251,52 +226,13 @@ dedup_and_flatten_args(PyObject* args)
  return new_args;
 }
 
-static int
-is_typevar(PyObject *obj)
-{
- return is_typing_name(obj, "TypeVar");
-}
-
-static int
-is_special_form(PyObject *obj)
-{
- return is_typing_name(obj, "_SpecialForm");
-}
-
-static int
-is_new_type(PyObject *obj)
-{
- PyTypeObject *type = Py_TYPE(obj);
- if (type != &PyFunction_Type) {
- return 0;
- }
- return is_typing_module(obj);
-}
-
-// Emulates short-circuiting behavior of the ``||`` operator
-// while also checking negative values.
-#define CHECK_RES(res) { \
- int result = res; \
- if (result) { \
- return result; \
- } \
-}
-
-// Returns 1 on true, 0 on false, and -1 on error.
 static int
 is_unionable(PyObject *obj)
 {
- if (obj == Py_None ||
+ return (obj == Py_None ||
  PyType_Check(obj) ||
  _PyGenericAlias_Check(obj) ||
- _PyUnion_Check(obj))
- {
- return 1;
- }
- CHECK_RES(is_typevar(obj));
- CHECK_RES(is_new_type(obj));
- CHECK_RES(is_special_form(obj));
- return 0;
+ _PyUnion_Check(obj));
 }
 
 static int
@@ -305,12 +241,9 @@ is_args_unionable(PyObject *args)
  Py_ssize_t nargs = PyTuple_GET_SIZE(args);
  for (Py_ssize_t iarg = 0; iarg < nargs; iarg++) {
  PyObject *arg = PyTuple_GET_ITEM(args, iarg);
- int is_arg_unionable = is_unionable(arg);
- if (is_arg_unionable <= 0) {
- if (is_arg_unionable == 0) {
- PyErr_Format(PyExc_TypeError,
- "Each union argument must be a type, got %.100R", arg);
- }
+ if (!is_unionable(arg)) {
+ PyErr_Format(PyExc_TypeError,
+ "Each union argument must be a type, got %.100R", arg);
  return 0;
  }
  }
@@ -320,14 +253,7 @@ is_args_unionable(PyObject *args)
 PyObject *
 _Py_union_type_or(PyObject* self, PyObject* other)
 {
- int r = is_unionable(self);
- if (r > 0) {
- r = is_unionable(other);
- }
- if (r < 0) {
- return NULL;
- }
- if (!r) {
+ if (!is_unionable(self) || !is_unionable(other)) {
  Py_RETURN_NOTIMPLEMENTED;
  }
 
@@ -465,7 +391,7 @@ union_from_args(PyObject *cls, PyObject *args)
  return NULL;
  }
 
- if (is_args_unionable(args) <= 0) {
+ if (!is_args_unionable(args)) {
  return NULL;
  }