8000 gh-88965: typing: fix type substitution of a list of types after ini… · python/cpython@adb0621 · GitHub
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gh-88965: typing: fix type substitution of a list of types after initial ParamSpec substitution (#102808)
Previously, this used to fail: ```py from typing import * T = TypeVar("T") P = ParamSpec("P") class X(Generic[P]): f: Callable[P, int] Y = X[[int, T]] Z = Y[str] ``` Co-authored-by: Alex Waygood <Alex.Waygood@Gmail.com>
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‎Lib/test/test_typing.py

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Original file line numberDiff line numberDiff line change
@@ -7679,6 +7679,127 @@ def test_bad_var_substitution(self):
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with self.assertRaises(TypeError):
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collections.abc.Callable[P, T][arg, str]
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7682+
def test_type_var_subst_for_other_type_vars(self):
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T = TypeVar('T')
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T2 = TypeVar('T2')
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P = ParamSpec('P')
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P2 = ParamSpec('P2')
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Ts = TypeVarTuple('Ts')
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class Base(Generic[P]):
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pass
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A1 = Base[T]
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self.assertEqual(A1.__parameters__, (T,))
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self.assertEqual(A1.__args__, ((T,),))
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self.assertEqual(A1[int], Base[int])
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A2 = Base[[T]]
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self.assertEqual(A2.__parameters__, (T,))
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self.assertEqual(A2.__args__, ((T,),))
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self.assertEqual(A2[int], Base[int])
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A3 = Base[[int, T]]
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self.assertEqual(A3.__parameters__, (T,))
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self.assertEqual(A3.__args__, ((int, T),))
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self.assertEqual(A3[str], Base[[int, str]])
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A4 = Base[[T, int, T2]]
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self.assertEqual(A4.__parameters__, (T, T2))
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self.assertEqual(A4.__args__, ((T, int, T2),))
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self.assertEqual(A4[str, bool], Base[[str, int, bool]])
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A5 = Base[[*Ts, int]]
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self.assertEqual(A5.__parameters__, (Ts,))
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self.assertEqual(A5.__args__, ((*Ts, int),))
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self.assertEqual(A5[str, bool], Base[[str, bool, int]])
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A5_2 = Base[[int, *Ts]]
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self.assertEqual(A5_2.__parameters__, (Ts,))
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self.assertEqual(A5_2.__args__, ((int, *Ts),))
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self.assertEqual(A5_2[str, bool], Base[[int, str, bool]])
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A6 = Base[[T, *Ts]]
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self.assertEqual(A6.__parameters__, (T, Ts))
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self.assertEqual(A6.__args__, ((T, *Ts),))
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self.assertEqual(A6[int, str, bool], Base[[int, str, bool]])
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A7 = Base[[T, T]]
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self.assertEqual(A7.__parameters__, (T,))
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self.assertEqual(A7.__args__, ((T, T),))
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self.assertEqual(A7[int], Base[[int, int]])
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A8 = Base[[T, list[T]]]
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self.assertEqual(A8.__parameters__, (T,))
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self.assertEqual(A8.__args__, ((T, list[T]),))
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self.assertEqual(A8[int], Base[[int, list[int]]])
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A9 = Base[[Tuple[*Ts], *Ts]]
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self.assertEqual(A9.__parameters__, (Ts,))
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self.assertEqual(A9.__args__, ((Tuple[*Ts], *Ts),))
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self.assertEqual(A9[int, str], Base[Tuple[int, str], int, str])
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A10 = Base[P2]
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self.assertEqual(A10.__parameters__, (P2,))
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self.assertEqual(A10.__args__, (P2,))
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self.assertEqual(A10[[int, str]], Base[[int, str]])
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class DoubleP(Generic[P, P2]):
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pass
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B1 = DoubleP[P, P2]
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self.assertEqual(B1.__parameters__, (P, P2))
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self.assertEqual(B1.__args__, (P, P2))
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self.assertEqual(B1[[int, str], [bool]], DoubleP[[int, str], [bool]])
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self.assertEqual(B1[[], []], DoubleP[[], []])
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B2 = DoubleP[[int, str], P2]
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self.assertEqual(B2.__parameters__, (P2,))
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self.assertEqual(B2.__args__, ((int, str), P2))
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self.assertEqual(B2[[bool, bool]], DoubleP[[int, str], [bool, bool]])
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self.assertEqual(B2[[]], DoubleP[[int, str], []])
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B3 = DoubleP[P, [bool, bool]]
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self.assertEqual(B3.__parameters__, (P,))
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self.assertEqual(B3.__args__, (P, (bool, bool)))
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self.assertEqual(B3[[int, str]], DoubleP[[int, str], [bool, bool]])
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self.assertEqual(B3[[]], DoubleP[[], [bool, bool]])
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B4 = DoubleP[[T, int], [bool, T2]]
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self.assertEqual(B4.__parameters__, (T, T2))
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self.assertEqual(B4.__args__, ((T, int), (bool, T2)))
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self.assertEqual(B4[str, float], DoubleP[[str, int], [bool, float]])
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B5 = DoubleP[[*Ts, int], [bool, T2]]
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self.assertEqual(B5.__parameters__, (Ts, T2))
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self.assertEqual(B5.__args__, ((*Ts, int), (bool, T2)))
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self.assertEqual(B5[str, bytes, float],
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DoubleP[[str, bytes, int], [bool, float]])
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B6 = DoubleP[[T, int], [bool, *Ts]]
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self.assertEqual(B6.__parameters__, (T, Ts))
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self.assertEqual(B6.__args__, ((T, int), (bool, *Ts)))
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self.assertEqual(B6[str, bytes, float],
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DoubleP[[str, int], [bool, bytes, float]])
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class PandT(Generic[P, T]):
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pass
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C1 = PandT[P, T]
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self.assertEqual(C1.__parameters__, (P, T))
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self.assertEqual(C1.__args__, (P, T))
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self.assertEqual(C1[[int, str], bool], PandT[[int, str], bool])
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C2 = PandT[[int, T], T]
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self.assertEqual(C2.__parameters__, (T,))
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self.assertEqual(C2.__args__, ((int, T), T))
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self.assertEqual(C2[str], PandT[[int, str], str])
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C3 = PandT[[int, *Ts], T]
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self.assertEqual(C3.__parameters__, (Ts, T))
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self.assertEqual(C3.__args__, ((int, *Ts), T))
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self.assertEqual(C3[str, bool, bytes], PandT[[int, str, bool], bytes])
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def test_paramspec_in_nested_generics(self):
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# Although ParamSpec should not be found in __parameters__ of most
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# generics, they probably should be found when nested in

‎Lib/typing.py

Lines changed: 26 additions & 7 deletions
Original file line numberDiff line numberDiff line change
@@ -255,10 +255,17 @@ def _collect_parameters(args):
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"""
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parameters = []
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for t in args:
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# We don't want __parameters__ descriptor of a bare Python class.
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if isinstance(t, type):
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continue
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if hasattr(t, '__typing_subst__'):
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# We don't want __parameters__ descriptor of a bare Python class.
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pass
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elif isinstance(t, tuple):
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# `t` might be a tuple, when `ParamSpec` is substituted with
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# `[T, int]`, or `[int, *Ts]`, etc.
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for x in t:
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for collected in _collect_parameters([x]):
266+
if collected not in parameters:
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parameters.append(collected)
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elif hasattr(t, '__typing_subst__'):
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if t not in parameters:
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parameters.append(t)
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else:
@@ -1441,10 +1448,12 @@ def _determine_new_args(self, args):
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raise TypeError(f"Too {'many' if alen > plen else 'few'} arguments for {self};"
14421449
f" actual {alen}, expected {plen}")
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new_arg_by_param = dict(zip(params, args))
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return tuple(self._make_substitution(self.__args__, new_arg_by_param))
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def _make_substitution(self, args, new_arg_by_param):
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"""Create a list of new type arguments."""
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new_args = []
1446-
for old_arg in self.__args__:
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for old_arg in args:
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if isinstance(old_arg, type):
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new_args.append(old_arg)
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continue
@@ -1488,10 +1497,20 @@ def _determine_new_args(self, args):
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# should join all these types together in a flat list
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# `(float, int, str)` - so again, we should `extend`.
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new_args.extend(new_arg)
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elif isinstance(old_arg, tuple):
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# Corner case:
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# P = ParamSpec('P')
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# T = TypeVar('T')
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# class Base(Generic[P]): ...
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# Can be substituted like this:
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# X = Base[[int, T]]
1507+
# In this case, `old_arg` will be a tuple:
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new_args.append(
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tuple(self._make_substitution(old_arg, new_arg_by_param)),
1510+
)
14911511
else:
14921512
new_args.append(new_arg)
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1494-
return tuple(new_args)
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return new_args
14951514

14961515
def copy_with(self, args):
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return self.__class__(self.__origin__, args, name=self._name, inst=self._inst,

‎Misc/NEWS.d/next/Library/2023-03-18-14-59-21.gh-issue-88965.kA70Km.rst

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@@ -0,0 +1,7 @@
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typing: Fix a bug relating to substitution in custom classes generic over a
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:class:`~typing.ParamSpec`. Previously, if the ``ParamSpec`` was substituted
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with a parameters list that itself contained a :class:`~typing.TypeVar`, the
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``TypeVar`` in the parameters list could not be subsequently substituted. This
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is now fixed.
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Patch by Nikita Sobolev.

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