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Merged
dcreager merged 4 commits into from
Dec 13, 2025
Merged

[ty] Allow gradual lower/upper bounds in a constraint set #21957

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40b5666
allow gradual bounds
dcreager Dec 12, 2025
7d5b1e5
add some more tests
dcreager Dec 12, 2025
0d90fe7
order specialized types consistently
dcreager Dec 13, 2025
431a9d3
Merge remote-tracking branch 'origin/main' into dcreager/gradual-bounds
dcreager Dec 13, 2025
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84 changes: 81 additions & 3 deletions crates/ty_python_semantic/resources/mdtest/generics/specialize_constrained.md
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Original file line number Diff line number Diff line change
Expand Up @@ -16,7 +16,7 @@ An unbounded typevar can specialize to any type. We will specialize the typevar
bound of all of the types that satisfy the constraint set.

```py
from typing import Never
from typing import Any, Never
from ty_extensions import ConstraintSet, generic_context

# fmt: off
Expand All @@ -26,6 +26,8 @@ def unbounded[T]():
reveal_type(generic_context(unbounded).specialize_constrained(ConstraintSet.always()))
# revealed: ty_extensions.Specialization[T@unbounded = object]
reveal_type(generic_context(unbounded).specialize_constrained(ConstraintSet.range(Never, T, object)))
# revealed: ty_extensions.Specialization[T@unbounded = Any]
reveal_type(generic_context(unbounded).specialize_constrained(ConstraintSet.range(Never, T, Any)))
# revealed: None
reveal_type(generic_context(unbounded).specialize_constrained(ConstraintSet.never()))

Expand Down Expand Up @@ -68,6 +70,10 @@ class Unrelated: ...
def bounded[T: Base]():
# revealed: ty_extensions.Specialization[T@bounded = Base]
reveal_type(generic_context(bounded).specialize_constrained(ConstraintSet.always()))
# revealed: ty_extensions.Specialization[T@bounded = Base]
reveal_type(generic_context(bounded).specialize_constrained(ConstraintSet.range(Never, T, object)))
# revealed: ty_extensions.Specialization[T@bounded = Base & Any]
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@carljm carljm Dec 12, 2025

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Nice, this seems like the right solution here

reveal_type(generic_context(bounded).specialize_constrained(ConstraintSet.range(Never, T, Any)))
# revealed: None
reveal_type(generic_context(bounded).specialize_constrained(ConstraintSet.never()))

Expand All @@ -94,26 +100,42 @@ def bounded_by_gradual[T: Any]():
# TODO: revealed: ty_extensions.Specialization[T@bounded_by_gradual = Any]
# revealed: ty_extensions.Specialization[T@bounded_by_gradual = object]
reveal_type(generic_context(bounded_by_gradual).specialize_constrained(ConstraintSet.always()))
# revealed: ty_extensions.Specialization[T@bounded_by_gradual = object]
reveal_type(generic_context(bounded_by_gradual).specialize_constrained(ConstraintSet.range(Never, T, object)))
# revealed: ty_extensions.Specialization[T@bounded_by_gradual = Any]
reveal_type(generic_context(bounded_by_gradual).specialize_constrained(ConstraintSet.range(Never, T, Any)))
# revealed: None
reveal_type(generic_context(bounded_by_gradual).specialize_constrained(ConstraintSet.never()))

# revealed: ty_extensions.Specialization[T@bounded_by_gradual = Base]
reveal_type(generic_context(bounded_by_gradual).specialize_constrained(ConstraintSet.range(Never, T, Base)))
# revealed: ty_extensions.Specialization[T@bounded_by_gradual = object]
reveal_type(generic_context(bounded_by_gradual).specialize_constrained(ConstraintSet.range(Base, T, object)))

# revealed: ty_extensions.Specialization[T@bounded_by_gradual = Unrelated]
reveal_type(generic_context(bounded_by_gradual).specialize_constrained(ConstraintSet.range(Never, T, Unrelated)))

def bounded_by_gradual_list[T: list[Any]]():
# revealed: ty_extensions.Specialization[T@bounded_by_gradual_list = Top[list[Any]]]
reveal_type(generic_context(bounded_by_gradual_list).specialize_constrained(ConstraintSet.always()))
# revealed: ty_extensions.Specialization[T@bounded_by_gradual_list = list[object]]
reveal_type(generic_context(bounded_by_gradual_list).specialize_constrained(ConstraintSet.range(Never, T, list[object])))
# revealed: ty_extensions.Specialization[T@bounded_by_gradual_list = list[Any]]
reveal_type(generic_context(bounded_by_gradual_list).specialize_constrained(ConstraintSet.range(Never, T, list[Any])))
# revealed: None
reveal_type(generic_context(bounded_by_gradual_list).specialize_constrained(ConstraintSet.never()))

# revealed: ty_extensions.Specialization[T@bounded_by_gradual_list = list[Base]]
reveal_type(generic_context(bounded_by_gradual_list).specialize_constrained(ConstraintSet.range(Never, T, list[Base])))
# TODO: revealed: ty_extensions.Specialization[T@bounded_by_gradual_list = list[Base]]
# revealed: ty_extensions.Specialization[T@bounded_by_gradual_list = Top[list[Any]]]
reveal_type(generic_context(bounded_by_gradual_list).specialize_constrained(ConstraintSet.range(list[Base], T, object)))

# revealed: ty_extensions.Specialization[T@bounded_by_gradual_list = list[Unrelated]]
reveal_type(generic_context(bounded_by_gradual_list).specialize_constrained(ConstraintSet.range(Never, T, list[Unrelated])))
# TODO: revealed: ty_extensions.Specialization[T@bounded_by_gradual_list = list[Unrelated]]
# revealed: ty_extensions.Specialization[T@bounded_by_gradual_list = Top[list[Any]]]
reveal_type(generic_context(bounded_by_gradual_list).specialize_constrained(ConstraintSet.range(list[Unrelated], T, object)))
```

## Constrained typevar
Expand Down Expand Up @@ -142,12 +164,21 @@ def constrained[T: (Base, Unrelated)]():
# revealed: None
reveal_type(generic_context(constrained).specialize_constrained(ConstraintSet.always()))
# revealed: None
reveal_type(generic_context(constrained).specialize_constrained(ConstraintSet.range(Never, T, object)))
# revealed: None
reveal_type(generic_context(constrained).specialize_constrained(ConstraintSet.range(Never, T, Any)))
Comment on lines 166 to +169
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@carljm carljm Dec 12, 2025

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These are None because we have no basis for picking between Base and Unrelated, so we'll just fall back to Unknown?

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@dcreager dcreager Dec 13, 2025

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That's right

# revealed: None
reveal_type(generic_context(constrained).specialize_constrained(ConstraintSet.never()))

# revealed: ty_extensions.Specialization[T@constrained = Base]
reveal_type(generic_context(constrained).specialize_constrained(ConstraintSet.range(Never, T, Base)))
# revealed: ty_extensions.Specialization[T@constrained = Base]
reveal_type(generic_context(constrained).specialize_constrained(ConstraintSet.range(Base, T, object)))

# revealed: ty_extensions.Specialization[T@constrained = Unrelated]
reveal_type(generic_context(constrained).specialize_constrained(ConstraintSet.range(Never, T, Unrelated)))
# revealed: ty_extensions.Specialization[T@constrained = Unrelated]
reveal_type(generic_context(constrained).specialize_constrained(ConstraintSet.range(Unrelated, T, object)))

# revealed: ty_extensions.Specialization[T@constrained = Base]
reveal_type(generic_context(constrained).specialize_constrained(ConstraintSet.range(Never, T, Super)))
Expand Down Expand Up @@ -178,15 +209,25 @@ def constrained_by_gradual[T: (Base, Any)]():
# TODO: revealed: ty_extensions.Specialization[T@constrained_by_gradual = Any]
# revealed: ty_extensions.Specialization[T@constrained_by_gradual = Base]
reveal_type(generic_context(constrained_by_gradual).specialize_constrained(ConstraintSet.range(Never, T, object)))
# TODO: revealed: ty_extensions.Specialization[T@constrained_by_gradual = Any]
# revealed: ty_extensions.Specialization[T@constrained_by_gradual = Base & Any]
reveal_type(generic_context(constrained_by_gradual).specialize_constrained(ConstraintSet.range(Never, T, Any)))
# revealed: None
reveal_type(generic_context(constrained_by_gradual).specialize_constrained(ConstraintSet.never()))

# TODO: revealed: ty_extensions.Specialization[T@constrained_by_gradual = Any]
# revealed: ty_extensions.Specialization[T@constrained_by_gradual = Base]
reveal_type(generic_context(constrained_by_gradual).specialize_constrained(ConstraintSet.range(Never, T, Base)))
# TODO: revealed: ty_extensions.Specialization[T@constrained_by_gradual = Any]
# revealed: ty_extensions.Specialization[T@constrained_by_gradual = Base]
reveal_type(generic_context(constrained_by_gradual).specialize_constrained(ConstraintSet.range(Base, T, object)))

# TODO: revealed: ty_extensions.Specialization[T@constrained_by_gradual = Any]
# revealed: ty_extensions.Specialization[T@constrained_by_gradual = Unrelated]
reveal_type(generic_context(constrained_by_gradual).specialize_constrained(ConstraintSet.range(Never, T, Unrelated)))
# TODO: revealed: ty_extensions.Specialization[T@constrained_by_gradual = Any]
# revealed: ty_extensions.Specialization[T@constrained_by_gradual = object]
reveal_type(generic_context(constrained_by_gradual).specialize_constrained(ConstraintSet.range(Unrelated, T, object)))

# TODO: revealed: ty_extensions.Specialization[T@constrained_by_gradual = Any]
# revealed: ty_extensions.Specialization[T@constrained_by_gradual = Base]
Expand All @@ -206,6 +247,11 @@ def constrained_by_two_gradual[T: (Any, Any)]():
# TODO: revealed: ty_extensions.Specialization[T@constrained_by_gradual = Any]
# revealed: ty_extensions.Specialization[T@constrained_by_two_gradual = object]
reveal_type(generic_context(constrained_by_two_gradual).specialize_constrained(ConstraintSet.always()))
# TODO: revealed: ty_extensions.Specialization[T@constrained_by_two_gradual = Any]
# revealed: ty_extensions.Specialization[T@constrained_by_two_gradual = object]
reveal_type(generic_context(constrained_by_two_gradual).specialize_constrained(ConstraintSet.range(Never, T, object)))
# revealed: ty_extensions.Specialization[T@constrained_by_two_gradual = Any]
reveal_type(generic_context(constrained_by_two_gradual).specialize_constrained(ConstraintSet.range(Never, T, Any)))
# revealed: None
reveal_type(generic_context(constrained_by_two_gradual).specialize_constrained(ConstraintSet.never()))

Expand Down Expand Up @@ -233,14 +279,24 @@ def constrained_by_two_gradual[T: (Any, Any)]():
def constrained_by_gradual_list[T: (list[Base], list[Any])]():
# revealed: ty_extensions.Specialization[T@constrained_by_gradual_list = list[Base]]
reveal_type(generic_context(constrained_by_gradual_list).specialize_constrained(ConstraintSet.always()))
# revealed: ty_extensions.Specialization[T@constrained_by_gradual_list = list[object]]
reveal_type(generic_context(constrained_by_gradual_list).specialize_constrained(ConstraintSet.range(Never, T, list[object])))
# TODO: revealed: ty_extensions.Specialization[T@constrained_by_gradual_list = list[Any]]
# revealed: ty_extensions.Specialization[T@constrained_by_gradual_list = list[Base] & list[Any]]
reveal_type(generic_context(constrained_by_gradual_list).specialize_constrained(ConstraintSet.range(Never, T, list[Any])))
# revealed: None
reveal_type(generic_context(constrained_by_gradual_list).specialize_constrained(ConstraintSet.never()))

# revealed: ty_extensions.Specialization[T@constrained_by_gradual_list = list[Base]]
reveal_type(generic_context(constrained_by_gradual_list).specialize_constrained(ConstraintSet.range(Never, T, list[Base])))
# TODO: revealed: ty_extensions.Specialization[T@constrained_by_gradual = list[Any]]
# revealed: ty_extensions.Specialization[T@constrained_by_gradual_list = list[Base]]
reveal_type(generic_context(constrained_by_gradual_list).specialize_constrained(ConstraintSet.range(list[Base], T, object)))

# revealed: ty_extensions.Specialization[T@constrained_by_gradual_list = list[Unrelated]]
reveal_type(generic_context(constrained_by_gradual_list).specialize_constrained(ConstraintSet.range(Never, T, list[Unrelated])))
# TODO: revealed: ty_extensions.Specialization[T@constrained_by_gradual = list[Unrelated]]
# revealed: ty_extensions.Specialization[T@constrained_by_gradual_list = Top[list[Any]]]
reveal_type(generic_context(constrained_by_gradual_list).specialize_constrained(ConstraintSet.range(list[Unrelated], T, object)))

# TODO: revealed: ty_extensions.Specialization[T@constrained_by_gradual = list[Any]]
# revealed: ty_extensions.Specialization[T@constrained_by_gradual_list = list[Super]]
Expand All @@ -257,14 +313,25 @@ def constrained_by_gradual_list[T: (list[Base], list[Any])]():
def constrained_by_gradual_list_reverse[T: (list[Any], list[Base])]():
# revealed: ty_extensions.Specialization[T@constrained_by_gradual_list_reverse = list[Base]]
reveal_type(generic_context(constrained_by_gradual_list_reverse).specialize_constrained(ConstraintSet.always()))
# revealed: ty_extensions.Specialization[T@constrained_by_gradual_list_reverse = list[object]]
reveal_type(generic_context(constrained_by_gradual_list_reverse).specialize_constrained(ConstraintSet.range(Never, T, list[object])))
# TODO: revealed: ty_extensions.Specialization[T@constrained_by_gradual_list_reverse = list[Any]]
# revealed: ty_extensions.Specialization[T@constrained_by_gradual_list_reverse = list[Base] & list[Any]]
reveal_type(generic_context(constrained_by_gradual_list_reverse).specialize_constrained(ConstraintSet.range(Never, T, list[Any])))
# revealed: None
reveal_type(generic_context(constrained_by_gradual_list_reverse).specialize_constrained(ConstraintSet.never()))

# revealed: ty_extensions.Specialization[T@constrained_by_gradual_list_reverse = list[Base]]
reveal_type(generic_context(constrained_by_gradual_list_reverse).specialize_constrained(ConstraintSet.range(Never, T, list[Base])))
# revealed: ty_extensions.Specialization[T@constrained_by_gradual_list_reverse = list[Base]]
reveal_type(generic_context(constrained_by_gradual_list_reverse).specialize_constrained(ConstraintSet.range(list[Base], T, object)))

# TODO: revealed: ty_extensions.Specialization[T@constrained_by_gradual = list[Any]]
# revealed: ty_extensions.Specialization[T@constrained_by_gradual_list_reverse = list[Unrelated]]
reveal_type(generic_context(constrained_by_gradual_list_reverse).specialize_constrained(ConstraintSet.range(Never, T, list[Unrelated])))
# TODO: revealed: ty_extensions.Specialization[T@constrained_by_gradual = list[Unrelated]]
# revealed: ty_extensions.Specialization[T@constrained_by_gradual_list_reverse = Top[list[Any]]]
reveal_type(generic_context(constrained_by_gradual_list_reverse).specialize_constrained(ConstraintSet.range(list[Unrelated], T, object)))

# TODO: revealed: ty_extensions.Specialization[T@constrained_by_gradual = list[Any]]
# revealed: ty_extensions.Specialization[T@constrained_by_gradual_list_reverse = list[Super]]
Expand All @@ -280,15 +347,26 @@ def constrained_by_two_gradual_lists[T: (list[Any], list[Any])]():
# TODO: revealed: ty_extensions.Specialization[T@constrained_by_gradual = list[Any]]
# revealed: ty_extensions.Specialization[T@constrained_by_two_gradual_lists = Top[list[Any]]]
reveal_type(generic_context(constrained_by_two_gradual_lists).specialize_constrained(ConstraintSet.always()))
# TODO: revealed: ty_extensions.Specialization[T@constrained_by_two_gradual_lists = list[Any]]
# revealed: ty_extensions.Specialization[T@constrained_by_two_gradual_lists = Top[list[Any]]]
reveal_type(generic_context(constrained_by_two_gradual_lists).specialize_constrained(ConstraintSet.range(Never, T, object)))
# revealed: ty_extensions.Specialization[T@constrained_by_two_gradual_lists = list[Any]]
reveal_type(generic_context(constrained_by_two_gradual_lists).specialize_constrained(ConstraintSet.range(Never, T, list[Any])))
# revealed: None
reveal_type(generic_context(constrained_by_two_gradual_lists).specialize_constrained(ConstraintSet.never()))

# TODO: revealed: ty_extensions.Specialization[T@constrained_by_gradual = list[Any]]
# revealed: ty_extensions.Specialization[T@constrained_by_two_gradual_lists = list[Base]]
reveal_type(generic_context(constrained_by_two_gradual_lists).specialize_constrained(ConstraintSet.range(Never, T, list[Base])))
# TODO: revealed: ty_extensions.Specialization[T@constrained_by_gradual = list[Base]]
# revealed: ty_extensions.Specialization[T@constrained_by_two_gradual_lists = Top[list[Any]]]
reveal_type(generic_context(constrained_by_two_gradual_lists).specialize_constrained(ConstraintSet.range(list[Base], T, object)))

# TODO: revealed: ty_extensions.Specialization[T@constrained_by_gradual = list[Any]]
# revealed: ty_extensions.Specialization[T@constrained_by_two_gradual_lists = list[Unrelated]]
reveal_type(generic_context(constrained_by_two_gradual_lists).specialize_constrained(ConstraintSet.range(Never, T, list[Unrelated])))
# TODO: revealed: ty_extensions.Specialization[T@constrained_by_gradual = list[Unrelated]]
# revealed: ty_extensions.Specialization[T@constrained_by_two_gradual_lists = Top[list[Any]]]
reveal_type(generic_context(constrained_by_two_gradual_lists).specialize_constrained(ConstraintSet.range(list[Unrelated], T, object)))

# TODO: revealed: ty_extensions.Specialization[T@constrained_by_gradual = list[Any]]
# revealed: ty_extensions.Specialization[T@constrained_by_two_gradual_lists = list[Super]]
Expand Down
28 changes: 25 additions & 3 deletions crates/ty_python_semantic/src/types/builder.rs
View file
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Original file line number Diff line number Diff line change
Expand Up @@ -668,28 +668,41 @@ pub(crate) struct IntersectionBuilder<'db> {
// but if a union is added to the intersection, we'll distribute ourselves over that union and
// create a union of intersections.
intersections: Vec<InnerIntersectionBuilder<'db>>,
order_elements: bool,
db: &'db dyn Db,
}

impl<'db> IntersectionBuilder<'db> {
pub(crate) fn new(db: &'db dyn Db) -> Self {
Self {
db,
order_elements: false,
intersections: vec![InnerIntersectionBuilder::default()],
}
}

fn empty(db: &'db dyn Db) -> Self {
Self {
db,
order_elements: false,
intersections: vec![],
}
}

pub(crate) fn order_elements(mut self, val: bool) -> Self {
self.order_elements = val;
self
}

pub(crate) fn add_positive(self, ty: Type<'db>) -> Self {
self.add_positive_impl(ty, &mut vec![])
}

pub(crate) fn add_positive_in_place(&mut self, ty: Type<'db>) {
let updated = std::mem::replace(self, Self::empty(self.db)).add_positive(ty);
*self = updated;
}

pub(crate) fn add_positive_impl(
mut self,
ty: Type<'db>,
Expand Down Expand Up @@ -898,13 +911,16 @@ impl<'db> IntersectionBuilder<'db> {
pub(crate) fn build(mut self) -> Type<'db> {
// Avoid allocating the UnionBuilder unnecessarily if we have just one intersection:
if self.intersections.len() == 1 {
self.intersections.pop().unwrap().build(self.db)
self.intersections
.pop()
.unwrap()
.build(self.db, self.order_elements)
} else {
UnionType::from_elements(
self.db,
self.intersections
.into_iter()
.map(|inner| inner.build(self.db)),
.map(|inner| inner.build(self.db, self.order_elements)),
)
}
}
Expand Down Expand Up @@ -1238,7 +1254,7 @@ impl<'db> InnerIntersectionBuilder<'db> {
}
}

fn build(mut self, db: &'db dyn Db) -> Type<'db> {
fn build(mut self, db: &'db dyn Db, order_elements: bool) -> Type<'db> {
self.simplify_constrained_typevars(db);

// If any typevars are in `self.positive`, speculatively solve all bounded type variables
Expand Down Expand Up @@ -1279,6 +1295,12 @@ impl<'db> InnerIntersectionBuilder<'db> {
_ => {
self.positive.shrink_to_fit();
self.negative.shrink_to_fit();
if order_elements {
self.positive
.sort_unstable_by(|l, r| union_or_intersection_elements_ordering(db, l, r));
self.negative
.sort_unstable_by(|l, r| union_or_intersection_elements_ordering(db, l, r));
}
Type::Intersection(IntersectionType::new(db, self.positive, self.negative))
}
}
Expand Down
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