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[ty] Allow tuple[Any, ...] to assign to tuple[int, *tuple[int, ...]] #21803

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Merged
charliermarsh merged 2 commits into from
Dec 5, 2025
Merged

[ty] Allow tuple[Any, ...] to assign to tuple[int, *tuple[int, ...]] #21803

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c7cf881
Allow tuple[Any, ...] to assign to tuple[int, *tuple[int, ...]]
charliermarsh Dec 5, 2025
bc4cc80
Add test
charliermarsh Dec 5, 2025
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10 changes: 10 additions & 0 deletions crates/ty_python_semantic/resources/mdtest/type_properties/is_assignable_to.md
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Original file line number Diff line number Diff line change
Expand Up @@ -537,6 +537,9 @@ static_assert(is_assignable_to(tuple[Any, ...], tuple[Any, Any]))
static_assert(is_assignable_to(tuple[Any, ...], tuple[int, ...]))
static_assert(is_assignable_to(tuple[Any, ...], tuple[int]))
static_assert(is_assignable_to(tuple[Any, ...], tuple[int, int]))
static_assert(is_assignable_to(tuple[Any, ...], tuple[int, *tuple[int, ...]]))
static_assert(is_assignable_to(tuple[Any, ...], tuple[*tuple[int, ...], int]))
static_assert(is_assignable_to(tuple[Any, ...], tuple[int, *tuple[int, ...], int]))
```

This also applies when `tuple[Any, ...]` is unpacked into a mixed tuple.
Expand All @@ -560,6 +563,10 @@ static_assert(is_assignable_to(tuple[*tuple[Any, ...], int], tuple[int, ...]))
static_assert(is_assignable_to(tuple[*tuple[Any, ...], int], tuple[int]))
static_assert(is_assignable_to(tuple[*tuple[Any, ...], int], tuple[int, int]))

# `*tuple[Any, ...]` can materialize to a tuple of any length as a special case,
# so this passes:
static_assert(is_assignable_to(tuple[*tuple[Any, ...], Any], tuple[*tuple[Any, ...], Any, Any]))

static_assert(is_assignable_to(tuple[int, *tuple[Any, ...], int], tuple[int, *tuple[Any, ...], int]))
static_assert(is_assignable_to(tuple[int, *tuple[Any, ...], int], tuple[Any, ...]))
static_assert(not is_assignable_to(tuple[int, *tuple[Any, ...], int], tuple[Any]))
Expand All @@ -580,6 +587,9 @@ static_assert(not is_assignable_to(tuple[int, ...], tuple[Any, Any]))
static_assert(is_assignable_to(tuple[int, ...], tuple[int, ...]))
static_assert(not is_assignable_to(tuple[int, ...], tuple[int]))
static_assert(not is_assignable_to(tuple[int, ...], tuple[int, int]))
static_assert(not is_assignable_to(tuple[int, ...], tuple[int, *tuple[int, ...]]))
static_assert(not is_assignable_to(tuple[int, ...], tuple[*tuple[int, ...], int]))
static_assert(not is_assignable_to(tuple[int, ...], tuple[int, *tuple[int, ...], int]))

static_assert(is_assignable_to(tuple[int, *tuple[int, ...]], tuple[int, *tuple[Any, ...]]))
static_assert(is_assignable_to(tuple[int, *tuple[int, ...]], tuple[Any, ...]))
Expand Down
36 changes: 30 additions & 6 deletions crates/ty_python_semantic/src/types/tuple.rs
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Expand Up @@ -994,10 +994,22 @@ impl<'db> VariableLengthTuple<Type<'db>> {
relation_visitor,
disjointness_visitor,
),
EitherOrBoth::Right(_) => {
EitherOrBoth::Right(other_ty) => {
// The rhs has a required element that the lhs is not guaranteed to
// provide.
return ConstraintSet::from(false);
// provide, unless the lhs has a dynamic variable-length portion
// that can materialize to provide it (for assignability only),
// as in `tuple[Any, ...]` matching `tuple[int, int]`.
if !relation.is_assignability() || !self.variable.is_dynamic() {
return ConstraintSet::from(false);
}
self.variable.has_relation_to_impl(
db,
other_ty,
inferable,
relation,
relation_visitor,
disjointness_visitor,
)
}
};
if result
Expand Down Expand Up @@ -1033,10 +1045,22 @@ impl<'db> VariableLengthTuple<Type<'db>> {
relation_visitor,
disjointness_visitor,
),
EitherOrBoth::Right(_) => {
EitherOrBoth::Right(other_ty) => {
// The rhs has a required element that the lhs is not guaranteed to
// provide.
return ConstraintSet::from(false);
// provide, unless the lhs has a dynamic variable-length portion
// that can materialize to provide it (for assignability only),
// as in `tuple[Any, ...]` matching `tuple[int, int]`.
if !relation.is_assignability() || !self.variable.is_dynamic() {
return ConstraintSet::from(false);
}
self.variable.has_relation_to_impl(
db,
*other_ty,
inferable,
relation,
relation_visitor,
disjointness_visitor,
)
}
};
if result
Expand Down
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