order specialized types consistently

crates/ty_python_semantic/resources/mdtest/generics/specialize_constrained.md

@@ -316,7 +316,7 @@ def constrained_by_gradual_list_reverse[T: (list[Any], list[Base])]():
     # 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[Any] & list[Base]]
+    # 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()))

crates/ty_python_semantic/src/types/builder.rs

@@ -668,6 +668,7 @@ 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,
 }
 
@@ -675,6 +676,7 @@ impl<'db> IntersectionBuilder<'db> {
     pub(crate) fn new(db: &'db dyn Db) -> Self {
         Self {
             db,
+            order_elements: false,
             intersections: vec![InnerIntersectionBuilder::default()],
         }
     }
@@ -682,14 +684,25 @@ impl<'db> IntersectionBuilder<'db> {
     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>,
@@ -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)),
             )
         }
     }
@@ -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
@@ -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))
             }
         }

crates/ty_python_semantic/src/types/constraints.rs

@@ -78,8 +78,8 @@ use salsa::plumbing::AsId;
 use crate::types::generics::{GenericContext, InferableTypeVars, Specialization};
 use crate::types::visitor::{TypeCollector, TypeVisitor, walk_type_with_recursion_guard};
 use crate::types::{
-    BoundTypeVarIdentity, BoundTypeVarInstance, IntersectionType, Type, TypeVarBoundOrConstraints,
+    BoundTypeVarIdentity, BoundTypeVarInstance, IntersectionBuilder, IntersectionType, Type,
-    UnionType, walk_bound_type_var_type,
+    TypeVarBoundOrConstraints, UnionBuilder, UnionType, walk_bound_type_var_type,
 };
 use crate::{Db, FxOrderSet};
 
@@ -3380,8 +3380,8 @@ impl<'db> GenericContext<'db> {
             // do with that, so instead we just report the ambiguity as a specialization failure.
             let mut satisfied = false;
             let mut unconstrained = false;
-            let mut greatest_lower_bound = Type::Never;
+            let mut greatest_lower_bound = UnionBuilder::new(db).order_elements(true);
-            let mut least_upper_bound = Type::object();
+            let mut least_upper_bound = IntersectionBuilder::new(db).order_elements(true);
             let identity = bound_typevar.identity(db);
             tracing::trace!(
                 target: "ty_python_semantic::types::constraints::specialize_constrained",
@@ -3400,10 +3400,8 @@ impl<'db> GenericContext<'db> {
                             upper_bound = %upper_bound.display(db),
                             "found representative type",
                         );
-                        greatest_lower_bound =
+                         greatest_lower_bound.add_in_place(lower_bound);
-                            UnionType::from_elements(db, [greatest_lower_bound, lower_bound]);
+                         least_upper_bound.add_positive_in_place(upper_bound);
-                        least_upper_bound =
-                            IntersectionType::from_elements(db, [least_upper_bound, upper_bound]);
                     }
                     None => {
                         unconstrained = true;
@@ -3437,6 +3435,8 @@ impl<'db> GenericContext<'db> {
 
             // If `lower ≰ upper`, then there is no type that satisfies all of the paths in the
             // BDD. That's an ambiguous specialization, as described above.
+            let greatest_lower_bound = greatest_lower_bound.build();
+            let least_upper_bound = least_upper_bound.build();
             if !greatest_lower_bound.is_assignable_to(db, least_upper_bound) {
                 tracing::debug!(
                     target: "ty_python_semantic::types::constraints::specialize_constrained",