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bpo-43224: Implement substitution of unpacked TypeVarTuple in C (GH-3…
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…1828)

Co-authored-by: Matthew Rahtz <mrahtz@gmail.com>
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@serhiy-storchaka
serhiy-storchaka and Matthew Rahtz authored Apr 30, 2022
1 parent a29aa76 commit e8c2f72
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Showing 5 changed files with 152 additions and 41 deletions.
1 change: 1 addition & 0 deletions Include/internal/pycore_global_strings.h
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Original file line number Diff line number Diff line change
Expand Up @@ -202,6 +202,7 @@ struct _Py_global_strings {
STRUCT_FOR_ID(__truediv__)
STRUCT_FOR_ID(__trunc__)
STRUCT_FOR_ID(__typing_subst__)
STRUCT_FOR_ID(__typing_unpacked__)
STRUCT_FOR_ID(__warningregistry__)
STRUCT_FOR_ID(__weakref__)
STRUCT_FOR_ID(__xor__)
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1 change: 1 addition & 0 deletions Include/internal/pycore_runtime_init.h
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Original file line number Diff line number Diff line change
Expand Up @@ -825,6 +825,7 @@ extern "C" {
INIT_ID(__truediv__), \
INIT_ID(__trunc__), \
INIT_ID(__typing_subst__), \
INIT_ID(__typing_unpacked__), \
INIT_ID(__warningregistry__), \
INIT_ID(__weakref__), \
INIT_ID(__xor__), \
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63 changes: 39 additions & 24 deletions Lib/test/test_typing.py
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Expand Up @@ -754,89 +754,89 @@ class C(Generic[*Ts]): pass
tests = [
# Alias # Args # Expected result
('C[*Ts]', '[()]', 'C[()]'),
('tuple[*Ts]', '[()]', 'TypeError'), # Should be tuple[()]
('tuple[*Ts]', '[()]', 'tuple[()]'),
('Tuple[*Ts]', '[()]', 'Tuple[()]'),

('C[*Ts]', '[int]', 'C[int]'),
('tuple[*Ts]', '[int]', 'tuple[(int,),]'), # Should be tuple[int]
('tuple[*Ts]', '[int]', 'tuple[int]'),
('Tuple[*Ts]', '[int]', 'Tuple[int]'),

('C[*Ts]', '[int, str]', 'C[int, str]'),
('tuple[*Ts]', '[int, str]', 'TypeError'), # Should be tuple[int, str]
('tuple[*Ts]', '[int, str]', 'tuple[int, str]'),
('Tuple[*Ts]', '[int, str]', 'Tuple[int, str]'),

('C[*Ts]', '[*tuple_type[int]]', 'C[*tuple_type[int]]'), # Should be C[int]
('tuple[*Ts]', '[*tuple_type[int]]', 'tuple[(*tuple_type[int],),]'), # Should be tuple[int]
('tuple[*Ts]', '[*tuple_type[int]]', 'tuple[*tuple_type[int]]'), # Should be tuple[int]
('Tuple[*Ts]', '[*tuple_type[int]]', 'Tuple[*tuple_type[int]]'), # Should be Tuple[int]

('C[*Ts]', '[*tuple_type[*Ts]]', 'C[*tuple_type[*Ts]]'), # Should be C[*Ts]
('tuple[*Ts]', '[*tuple_type[*Ts]]', 'tuple[(*tuple_type[*Ts],),]'), # Should be tuple[*Ts]
('tuple[*Ts]', '[*tuple_type[*Ts]]', 'tuple[*tuple_type[*Ts]]'), # Should be tuple[*Ts]
('Tuple[*Ts]', '[*tuple_type[*Ts]]', 'Tuple[*tuple_type[*Ts]]'), # Should be Tuple[*Ts]

('C[*Ts]', '[*tuple_type[int, str]]', 'C[*tuple_type[int, str]]'), # Should be C[int, str]
('tuple[*Ts]', '[*tuple_type[int, str]]', 'tuple[(*tuple_type[int, str],),]'), # Should be tuple[int, str]
('tuple[*Ts]', '[*tuple_type[int, str]]', 'tuple[*tuple_type[int, str]]'), # Should be tuple[int, str]
('Tuple[*Ts]', '[*tuple_type[int, str]]', 'Tuple[*tuple_type[int, str]]'), # Should be Tuple[int, str]

('C[*Ts]', '[tuple_type[int, ...]]', 'C[tuple_type[int, ...]]'),
('tuple[*Ts]', '[tuple_type[int, ...]]', 'tuple[(tuple_type[int, ...],),]'), # Should be tuple[tuple_type[int, ...]]
('tuple[*Ts]', '[tuple_type[int, ...]]', 'tuple[tuple_type[int, ...]]'),
('Tuple[*Ts]', '[tuple_type[int, ...]]', 'Tuple[tuple_type[int, ...]]'),

('C[*Ts]', '[tuple_type[int, ...], tuple_type[str, ...]]', 'C[tuple_type[int, ...], tuple_type[str, ...]]'),
('tuple[*Ts]', '[tuple_type[int, ...], tuple_type[str, ...]]', 'TypeError'), # Should be tuple[tuple_type[int, ...], tuple_type[str, ...]]
('tuple[*Ts]', '[tuple_type[int, ...], tuple_type[str, ...]]', 'tuple[tuple_type[int, ...], tuple_type[str, ...]]'),
('Tuple[*Ts]', '[tuple_type[int, ...], tuple_type[str, ...]]', 'Tuple[tuple_type[int, ...], tuple_type[str, ...]]'),

('C[*Ts]', '[*tuple_type[int, ...]]', 'C[*tuple_type[int, ...]]'),
('tuple[*Ts]', '[*tuple_type[int, ...]]', 'tuple[(*tuple_type[int, ...],),]'), # Should be tuple[*tuple_type[int, ...]]
('tuple[*Ts]', '[*tuple_type[int, ...]]', 'tuple[*tuple_type[int, ...]]'),
('Tuple[*Ts]', '[*tuple_type[int, ...]]', 'Tuple[*tuple_type[int, ...]]'),

# Technically, multiple unpackings are forbidden by PEP 646, but we
# choose to be less restrictive at runtime, to allow folks room
# to experiment. So all three of these should be valid.
('C[*Ts]', '[*tuple_type[int, ...], *tuple_type[str, ...]]', 'C[*tuple_type[int, ...], *tuple_type[str, ...]]'),
# Should be tuple[*tuple_type[int, ...], *tuple_type[str, ...]], to match the other two.
('tuple[*Ts]', '[*tuple_type[int, ...], *tuple_type[str, ...]]', 'TypeError'),
('tuple[*Ts]', '[*tuple_type[int, ...], *tuple_type[str, ...]]', 'tuple[*tuple_type[int, ...], *tuple_type[str, ...]]'),
('Tuple[*Ts]', '[*tuple_type[int, ...], *tuple_type[str, ...]]', 'Tuple[*tuple_type[int, ...], *tuple_type[str, ...]]'),

('C[*Ts]', '[*Ts]', 'C[*Ts]'),
('tuple[*Ts]', '[*Ts]', 'tuple[(*Ts,),]'), # Should be tuple[*Ts]
('tuple[*Ts]', '[*Ts]', 'tuple[*Ts]'),
('Tuple[*Ts]', '[*Ts]', 'Tuple[*Ts]'),

('C[*Ts]', '[T, *Ts]', 'C[T, *Ts]'),
('tuple[*Ts]', '[T, *Ts]', 'TypeError'), # Should be tuple[T, *Ts]
('tuple[*Ts]', '[T, *Ts]', 'tuple[T, *Ts]'),
('Tuple[*Ts]', '[T, *Ts]', 'Tuple[T, *Ts]'),

('C[*Ts]', '[*Ts, T]', 'C[*Ts, T]'),
('tuple[*Ts]', '[*Ts, T]', 'TypeError'), # Should be tuple[*Ts, T]
('tuple[*Ts]', '[*Ts, T]', 'tuple[*Ts, T]'),
('Tuple[*Ts]', '[*Ts, T]', 'Tuple[*Ts, T]'),

('C[T, *Ts]', '[int]', 'C[int]'),
('tuple[T, *Ts]', '[int]', 'TypeError'), # Should be tuple[int]
('tuple[T, *Ts]', '[int]', 'tuple[int]'),
('Tuple[T, *Ts]', '[int]', 'Tuple[int]'),

('C[T, *Ts]', '[int, str]', 'C[int, str]'),
('tuple[T, *Ts]', '[int, str]', 'tuple[int, (str,)]'), # Should be tuple[int, str]
('tuple[T, *Ts]', '[int, str]', 'tuple[int, str]'),
('Tuple[T, *Ts]', '[int, str]', 'Tuple[int, str]'),

('C[T, *Ts]', '[int, str, bool]', 'C[int, str, bool]'),
('tuple[T, *Ts]', '[int, str, bool]', 'TypeError'), # Should be tuple[int, str, bool]
('tuple[T, *Ts]', '[int, str, bool]', 'tuple[int, str, bool]'),
('Tuple[T, *Ts]', '[int, str, bool]', 'Tuple[int, str, bool]'),

('C[T, *Ts]', '[*tuple[int, ...]]', 'C[*tuple[int, ...]]'), # Should be C[int, *tuple[int, ...]]
('C[T, *Ts]', '[*Tuple[int, ...]]', 'TypeError'), # Ditto
('tuple[T, *Ts]', '[*tuple_type[int, ...]]', 'TypeError'), # Should be tuple[int, *tuple[int, ...]]
('Tuple[T, *Ts]', '[*tuple[int, ...]]', 'Tuple[*tuple[int, ...]]'), # Ditto
('Tuple[T, *Ts]', '[*Tuple[int, ...]]', 'TypeError'), # Ditto
('tuple[T, *Ts]', '[*tuple[int, ...]]', 'tuple[*tuple[int, ...]]'), # Should be tuple[int, *tuple[int, ...]]
('tuple[T, *Ts]', '[*Tuple[int, ...]]', 'TypeError'), # Should be tuple[int, *Tuple[int, ...]]
('Tuple[T, *Ts]', '[*tuple[int, ...]]', 'Tuple[*tuple[int, ...]]'), # Should be Tuple[int, *tuple[int, ...]]
('Tuple[T, *Ts]', '[*Tuple[int, ...]]', 'TypeError'), # Should be Tuple[int, *Tuple[int, ...]]

('C[*Ts, T]', '[int]', 'C[int]'),
('tuple[*Ts, T]', '[int]', 'TypeError'), # Should be tuple[int]
('tuple[*Ts, T]', '[int]', 'tuple[int]'),
('Tuple[*Ts, T]', '[int]', 'Tuple[int]'),

('C[*Ts, T]', '[int, str]', 'C[int, str]'),
('tuple[*Ts, T]', '[int, str]', 'tuple[(int,), str]'), # Should be tuple[int, str]
('tuple[*Ts, T]', '[int, str]', 'tuple[int, str]'),
('Tuple[*Ts, T]', '[int, str]', 'Tuple[int, str]'),

('C[*Ts, T]', '[int, str, bool]', 'C[int, str, bool]'),
('tuple[*Ts, T]', '[int, str, bool]', 'TypeError'), # Should be tuple[int, str, bool]
('tuple[*Ts, T]', '[int, str, bool]', 'tuple[int, str, bool]'),
('Tuple[*Ts, T]', '[int, str, bool]', 'Tuple[int, str, bool]'),

('generic[T, *tuple_type[int, ...]]', '[str]', 'generic[str, *tuple_type[int, ...]]'),
Expand Down Expand Up @@ -945,7 +945,7 @@ def test_var_substitution(self):
T2 = TypeVar('T2')
class G(Generic[Unpack[Ts]]): pass

for A in G, Tuple:
for A in G, Tuple, tuple:
B = A[Unpack[Ts]]
self.assertEqual(B[()], A[()])
self.assertEqual(B[float], A[float])
Expand Down Expand Up @@ -984,6 +984,21 @@ def test_bad_var_substitution(self):
T2 = TypeVar('T2')
class G(Generic[Unpack[Ts]]): pass

for A in G, Tuple, tuple:
B = A[Ts]
with self.assertRaises(TypeError):
B[int, str]

C = A[T, T2]
with self.assertRaises(TypeError):
C[Unpack[Ts]]

def test_repr_is_correct(self):
Ts = TypeVarTuple('Ts')
T = TypeVar('T')
T2 = TypeVar('T2')
class G(Generic[Unpack[Ts]]): pass

for A in G, Tuple:
B = A[T, Unpack[Ts], str, T2]
with self.assertRaises(TypeError):
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10 changes: 7 additions & 3 deletions Lib/typing.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1019,7 +1019,7 @@ def __repr__(self):
return self.__name__

def __typing_subst__(self, arg):
raise AssertionError
raise TypeError("Substitution of bare TypeVarTuple is not supported")


class ParamSpecArgs(_Final, _Immutable, _root=True):
Expand Down Expand Up @@ -1686,11 +1686,15 @@ def __repr__(self):
return '*' + repr(self.__args__[0])

def __getitem__(self, args):
if (len(self.__parameters__) == 1 and
isinstance(self.__parameters__[0], TypeVarTuple)):
if self.__typing_unpacked__():
return args
return super().__getitem__(args)

def __typing_unpacked__(self):
# If x is Unpack[tuple[...]], __parameters__ will be empty.
return bool(self.__parameters__ and
isinstance(self.__parameters__[0], TypeVarTuple))


class Generic:
"""Abstract base class for generic types.
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