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Title: Rework starargs with union argument by randolf-scholz · Pull Request #19651 · python/mypy · GitHub

Open Graph Title: Rework starargs with union argument by randolf-scholz · Pull Request #19651 · python/mypy

X Title: Rework starargs with union argument by randolf-scholz · Pull Request #19651 · python/mypy

Description: Makes *args inference smarter by special casing UnionType *(tuple[A, B, C] | tuple[None|None|None]) gets treated like tuple[A | None, B | None, C | None] inside ArgTypeExpander (applies if all union member are fixed size tuples of equal length *(Iterable[X] | Iterable[Y]) gets treated like *Iterable[X | Y] inside ArgTypeExpander (applies if ① is not triggered) This gives some better inference in some cases: x: list[str | None] | list[str] reveal_type([*x]) # master: list[Any] PR: list[str | None] x2: tuple[int, int] | tuple[None, None] reveal_type( (*x2,) ) # master: tuple[Any, ...] PR: tuple[int | None, int | None] x3: tuple[int, int] | tuple[None, None, None] reveal_type( (*x3,) ) # master: tuple[Any, ...] PR: tuple[int | None, ...] See added unit tests for more examples. Fixes: #19662 Fixes: #19659 Fixes: #17161 Fixes: #15747 Fixes: #14470 Fixes: #15969 See Also: #19650, cc @hauntsaninja Dev notes: If we detect that the union has non-tuple elements or tuples of different sizes, we upcast-reinterpret every union member as some Iterable[T], then apply each union member, and then return the union of the results. Handling unions of finite size tuples with different sizes in infeasible, due to combinatoric explosion1 map_actuals_to_formals added special case for union of same sized tuples. ExpressionChecker.check_arg: added some extra logic that applies if the callee_type is UnpackType, but the actual_type got expanded from Unpack_type to something else. Previously, this only worked "by accident" because the expander was guaranteed to return AnyType(TypeOfAny.from_errors) in this case. ArgTypeExpander: Create a NewType alias IterableType for Iteralble[T], and helper functions is_iterable, is_iterable_instance_type, _make_iterable_instance_type. added _solve_as_iterable function that uses the solver to interpret a type as Iterable[T] added as_iterable_type that applies a few special cases (UnionType, etc. before calling the solver) added parse_star_args_type that converts the argument of *args to one of TupleType | IterableType | ParamSpecType | AnyType visit_tuple_expr: Applies ArgTypeExpander(*parse_star_args_type) to ensure consistent behavior across [*args], {*args} and (*args). Footnotes consider f(*x1, *x2, ..., *xn). If each $x_k$ is comprised of a union of $m_k$ differently sized tuples, then there are $m_1⋅m_2⋅…⋅m_k$ possible paths. ↩

Open Graph Description: Makes *args inference smarter by special casing UnionType *(tuple[A, B, C] | tuple[None|None|None]) gets treated like tuple[A | None, B | None, C | None] inside ArgTypeExpander (applies if all uni...

X Description: Makes *args inference smarter by special casing UnionType *(tuple[A, B, C] | tuple[None|None|None]) gets treated like tuple[A | None, B | None, C | None] inside ArgTypeExpander (applies if all uni...

Opengraph URL: https://github.com/python/mypy/pull/19651

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