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Add more tests for variable substitution in generics #31170

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Feb 6, 2022
Merged

Add more tests for variable substitution in generics #31170

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27 changes: 27 additions & 0 deletions Lib/test/test_typing.py
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Original file line number Diff line number Diff line change
Expand Up @@ -255,6 +255,15 @@ def test_no_bivariant(self):
with self.assertRaises(ValueError):
TypeVar('T', covariant=True, contravariant=True)

def test_bad_var_substitution(self):
T = TypeVar('T')
for arg in (), (int, str):
with self.subTest(arg=arg):
with self.assertRaises(TypeError):
List[T][arg]
with self.assertRaises(TypeError):
list[T][arg]


class UnionTests(BaseTestCase):

Expand Down Expand Up @@ -568,8 +577,11 @@ def test_var_substitution(self):
C2 = Callable[[KT, T], VT]
C3 = Callable[..., T]
self.assertEqual(C1[str], Callable[[int, str], str])
if Callable is typing.Callable:
self.assertEqual(C1[None], Callable[[int, type(None)], type(None)])
self.assertEqual(C2[int, float, str], Callable[[int, float], str])
self.assertEqual(C3[int], Callable[..., int])
self.assertEqual(C3[NoReturn], Callable[..., NoReturn])

# multi chaining
C4 = C2[int, VT, str]
Expand Down Expand Up @@ -4981,6 +4993,17 @@ class X(Generic[P, P2]):
self.assertEqual(G1.__args__, ((int, str), (bytes,)))
self.assertEqual(G2.__args__, ((int,), (str, bytes)))

def test_bad_var_substitution(self):
T = TypeVar('T')
P = ParamSpec('P')
bad_args = (42, int, None, T, int|str, Union[int, str])
for arg in bad_args:
with self.subTest(arg=arg):
with self.assertRaises(TypeError):
typing.Callable[P, T][arg, str]
with self.assertRaises(TypeError):
collections.abc.Callable[P, T][arg, str]

def test_no_paramspec_in__parameters__(self):
# ParamSpec should not be found in __parameters__
# of generics. Usages outside Callable, Concatenate
Expand Down Expand Up @@ -5010,6 +5033,10 @@ def test_paramspec_in_nested_generics(self):
self.assertEqual(G1.__parameters__, (P, T))
self.assertEqual(G2.__parameters__, (P, T))
self.assertEqual(G3.__parameters__, (P, T))
C = Callable[[int, str], float]
self.assertEqual(G1[[int, str], float], List[C])
self.assertEqual(G2[[int, str], float], list[C])
self.assertEqual(G3[[int, str], float], list[C] | int)


class ConcatenateTests(BaseTestCase):
Expand Down