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use smallest individual constraint

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Douglas Creager 2025-09-02 14:36:43 -04:00
parent 7abff51010
commit 0bca607ab6
1 changed files with 14 additions and 10 deletions
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24
crates/ty_python_semantic/src/types/generics.rs
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@ -19,7 +19,7 @@ use crate::types::{
ApplyTypeMappingVisitor, BoundTypeVarInstance, FindLegacyTypeVarsVisitor, HasRelationToVisitor,
IsEquivalentVisitor, KnownClass, KnownInstanceType, MaterializationKind, NormalizedVisitor,
Type, TypeMapping, TypeRelation, TypeVarBoundOrConstraints, TypeVarInstance, TypeVarKind,
TypeVarVariance, UnionBuilder, UnionType, binding_type, declaration_type,
TypeVarVariance, UnionType, binding_type, declaration_type,
};
use crate::{Db, FxOrderSet};
@ -1114,26 +1114,30 @@ impl<'db> SpecializationBuilder<'db> {
Some(TypeVarBoundOrConstraints::Constraints(constraints)) => {
// If the type is assignable to _all_ of the constraints, then we
// specialize the typevar to the type itself. If the type is assignable to
// some but not all of them, we specialize the type to the union of the
// constraints that it was assignable to. Otherwise it's a specialization
// error.
let mut builder = UnionBuilder::new(self.db);
// some but not all of them, we specialize the typevar to the "smallest"
// constraint that the type is assignable to. Otherwise it's a
// specialization error.
let mut when_all_assignable = ConstraintSet::from(true);
let mut any_assignable = false;
let mut smallest_assignable = None;
for constraint in constraints.elements(self.db) {
let when_assignable: ConstraintSet =
ty.when_assignable_to(self.db, *constraint);
if when_assignable.is_always_satisfied() {
builder = builder.add(*constraint);
any_assignable = true;
// If the type is assignable to this constraint individually. We
// only track the smallest such constraint.
if let Some(existing) = smallest_assignable.replace(*constraint) {
if existing.is_assignable_to(self.db, *constraint) {
smallest_assignable.replace(existing);
}
}
}
when_all_assignable.intersect(self.db, &when_assignable);
}
if when_all_assignable.is_always_satisfied() {
self.add_type_mapping(bound_typevar, ty);
} else if any_assignable {
self.add_type_mapping(bound_typevar, builder.build());
} else if let Some(smallest_assignable) = smallest_assignable {
self.add_type_mapping(bound_typevar, smallest_assignable);
} else {
return Err(SpecializationError::MismatchedConstraint {
bound_typevar,