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[3.11] typing: Add more tests for TypeVar (GH-104571) #104577

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Merged
JelleZijlstra merged 2 commits into from
May 17, 2023
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[3.11] typing: Add more tests for TypeVar (GH-104571) #104577

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[3.11] typing: Add more tests for TypeVar (GH-104571)
JelleZijlstra May 17, 2023
a1496e1
remove inapplicable test
JelleZijlstra May 17, 2023
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[3.11] typing: Add more tests for TypeVar (GH-104571) 
During the PEP 695 implementation at one point I made
TypeVar.__name__ return garbage, and all of test_typing passed.
So I decided to add a few more tests. In the process I discovered
a minor incompatibility from the C implementation of TypeVar:
empty constraints were returned as None instead of an empty tuple..
(cherry picked from commit 2693194)

Co-authored-by: Jelle Zijlstra <jelle.zijlstra@gmail.com>
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JelleZijlstra committed May 17, 2023
commit 856e8fd0888b284a88bacc60c824d22289af13d0
33 changes: 33 additions & 0 deletions Lib/test/test_typing.py
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Original file line number Diff line number Diff line change
Expand Up @@ -364,6 +364,32 @@ def test_basic_plain(self):
self.assertEqual(T, T)
# T is an instance of TypeVar
self.assertIsInstance(T, TypeVar)
self.assertEqual(T.__name__, 'T')
self.assertEqual(T.__constraints__, ())
self.assertIs(T.__bound__, None)
self.assertIs(T.__covariant__, False)
self.assertIs(T.__contravariant__, False)

def test_attributes(self):
T_bound = TypeVar('T_bound', bound=int)
self.assertEqual(T_bound.__name__, 'T_bound')
self.assertEqual(T_bound.__constraints__, ())
self.assertIs(T_bound.__bound__, int)

T_constraints = TypeVar('T_constraints', int, str)
self.assertEqual(T_constraints.__name__, 'T_constraints')
self.assertEqual(T_constraints.__constraints__, (int, str))
self.assertIs(T_constraints.__bound__, None)

T_co = TypeVar('T_co', covariant=True)
self.assertEqual(T_co.__name__, 'T_co')
self.assertIs(T_co.__covariant__, True)
self.assertIs(T_co.__contravariant__, False)

T_contra = TypeVar('T_contra', contravariant=True)
self.assertEqual(T_contra.__name__, 'T_contra')
self.assertIs(T_contra.__covariant__, False)
self.assertIs(T_contra.__contravariant__, True)

def test_typevar_instance_type_error(self):
T = TypeVar('T')
Expand Down Expand Up @@ -454,6 +480,12 @@ def test_no_bivariant(self):
with self.assertRaises(ValueError):
TypeVar('T', covariant=True, contravariant=True)

def test_cannot_combine_explicit_and_infer(self):
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with self.assertRaises(ValueError):
TypeVar('T', covariant=True, infer_variance=True)
with self.assertRaises(ValueError):
TypeVar('T', contravariant=True, infer_variance=True)

def test_var_substitution(self):
T = TypeVar('T')
subst = T.__typing_subst__
Expand Down Expand Up @@ -7426,6 +7458,7 @@ def test_basic_plain(self):
P = ParamSpec('P')
self.assertEqual(P, P)
self.assertIsInstance(P, ParamSpec)
self.assertEqual(P.__name__, 'P')

def test_valid_uses(self):
P = ParamSpec('P')
Expand Down