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Rework starargs with union argument #19651

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Rework starargs with union argument #19651

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245cba3
rework starargs with union argument
randolf-scholz Aug 13, 2025
f2d254c
Use typing.Unpack in tests
randolf-scholz Aug 14, 2025
df7b3f0
reworked argmapper with star args
randolf-scholz Aug 14, 2025
5e239a3
always use the solver meachnism
randolf-scholz Aug 15, 2025
6cbb237
fixed infer_constraints
randolf-scholz Aug 15, 2025
115bf00
cleanup
randolf-scholz Aug 15, 2025
08db3da
Merge branch 'master' into fix_list_comprehension
randolf-scholz Aug 15, 2025
fac1e07
address review
randolf-scholz Aug 15, 2025
68bc671
Merge branch 'python:master' into fix_list_comprehension
randolf-scholz Aug 15, 2025
e8dcf88
check paramspec flavor
randolf-scholz Aug 15, 2025
fe4289a
Revert "check paramspec flavor"
randolf-scholz Aug 15, 2025
0139c12
update parse_star_args_type docstring
randolf-scholz Aug 15, 2025
109b4f3
update parse_star_args_type docstring
randolf-scholz Aug 15, 2025
0a6d757
Merge branch 'master' into fix_list_comprehension
randolf-scholz Aug 16, 2025
e169d3e
address review
randolf-scholz Aug 16, 2025
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address review
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@randolf-scholz
randolf-scholz committed Aug 16, 2025
commit e169d3e33ac75a463c257aaf32d00ac0e0ee0cc8
28 changes: 15 additions & 13 deletions mypy/argmap.py
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Original file line number Diff line number Diff line change
Expand Up @@ -4,7 +4,7 @@

from collections.abc import Sequence
from typing import TYPE_CHECKING, Callable, cast
from typing_extensions import NewType, TypeGuard
from typing_extensions import NewType, TypeGuard, TypeIs

from mypy import nodes
from mypy.maptype import map_instance_to_supertype
Expand Down Expand Up @@ -278,11 +278,12 @@ def expand_actual_type(
return original_actual

def is_iterable(self, typ: Type) -> bool:
"""Check if the type is an iterable, i.e. implements the Iterable Protocol."""
from mypy.subtypes import is_subtype

return is_subtype(typ, self.context.iterable_type)

def is_iterable_instance_type(self, typ: Type) -> TypeGuard[IterableType]:
def is_iterable_instance_type(self, typ: Type) -> TypeIs[IterableType]:
"""Check if the type is an Iterable[T]."""
p_t = get_proper_type(typ)
return isinstance(p_t, Instance) and p_t.type == self.context.iterable_type.type
Expand All @@ -300,8 +301,6 @@ def _solve_as_iterable(self, typ: Type) -> IterableType | AnyType:
from mypy.nodes import ARG_POS
from mypy.solve import solve_constraints

iterable_kind = self.context.iterable_type.type

# We first create an upcast function:
# def [T] (Iterable[T]) -> Iterable[T]: ...
# and then solve for T, given the input type as the argument.
Expand All @@ -310,21 +309,20 @@ def _solve_as_iterable(self, typ: Type) -> IterableType | AnyType:
"T",
TypeVarId(-1),
values=[],
upper_bound=AnyType(TypeOfAny.special_form),
default=AnyType(TypeOfAny.special_form),
upper_bound=AnyType(TypeOfAny.from_omitted_generics),
default=AnyType(TypeOfAny.from_omitted_generics),
)
target = Instance(iterable_kind, [T])

target = self._make_iterable_instance_type(T)
upcast_callable = CallableType(
variables=[T],
arg_types=[target],
arg_kinds=[ARG_POS],
arg_names=[None],
ret_type=T,
ret_type=target,
fallback=self.context.function_type,
)
constraints = infer_constraints_for_callable(
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Can mypy.infer.infer_function_type_arguments replace this and following line at once?

upcast_callable, [typ], [ARG_POS], [None], [[0]], context=self.context
upcast_callable, [typ], [ARG_POS], [None], [[0]], self.context
)

(sol,), _ = solve_constraints([T], constraints)
Expand All @@ -334,7 +332,11 @@ def _solve_as_iterable(self, typ: Type) -> IterableType | AnyType:
return self._make_iterable_instance_type(sol)

def as_iterable_type(self, typ: Type) -> IterableType | AnyType:
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can we reuse logic from analyze_iterable_item_type_without_expression or similar?

"""Reinterpret a type as Iterable[T], or return AnyType if not possible."""
"""Reinterpret a type as Iterable[T], or return AnyType if not possible.

This function specially handles certain types like UnionType, TupleType, and UnpackType.
Otherwise, the upcasting is performed using the solver.
"""
p_t = get_proper_type(typ)
if self.is_iterable_instance_type(p_t) or isinstance(p_t, AnyType):
return p_t
Expand Down Expand Up @@ -386,8 +388,8 @@ def parse_star_args_type(
) -> TupleType | IterableType | ParamSpecType | AnyType:
"""Parse the type of a ``*args`` argument.

Returns one of TupleType, IterableType, ParamSpecType,
or AnyType(TypeOfAny.from_error) if the type cannot be parsed or is invalid.
Returns one of TupleType, IterableType, ParamSpecType or AnyType.
Returns AnyType(TypeOfAny.from_error) if the type cannot be parsed or is invalid.
"""
p_t = get_proper_type(typ)
if isinstance(p_t, (TupleType, ParamSpecType, AnyType)):
Expand Down
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