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[ty] Support narrowing on isinstance()/issubclass() if the second argument is a dynamic, intersection, union or typevar type (#18900)

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Alex Waygood 2025-06-24 11:55:26 +01:00 • committed by GitHub
parent fd2cc37f90
commit 27eee5a1a8
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3 changed files with 246 additions and 9 deletions
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79
crates/ty_python_semantic/src/types/narrow.rs
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@ -9,8 +9,8 @@ use crate::semantic_index::predicate::{
use crate::types::function::KnownFunction;
use crate::types::infer::infer_same_file_expression_type;
use crate::types::{
IntersectionBuilder, KnownClass, SubclassOfType, Truthiness, Type, UnionBuilder,
infer_expression_types,
ClassLiteral, ClassType, IntersectionBuilder, KnownClass, SubclassOfInner, SubclassOfType,
Truthiness, Type, TypeVarBoundOrConstraints, UnionBuilder, infer_expression_types,
};
use ruff_db::parsed::{ParsedModuleRef, parsed_module};
@ -167,9 +167,13 @@ impl ClassInfoConstraintFunction {
/// The `classinfo` argument can be a class literal, a tuple of (tuples of) class literals. PEP 604
/// union types are not yet supported. Returns `None` if the `classinfo` argument has a wrong type.
fn generate_constraint<'db>(self, db: &'db dyn Db, classinfo: Type<'db>) -> Option<Type<'db>> {
let constraint_fn = |class| match self {
ClassInfoConstraintFunction::IsInstance => Type::instance(db, class),
ClassInfoConstraintFunction::IsSubclass => SubclassOfType::from(db, class),
let constraint_fn = |class: ClassLiteral<'db>| match self {
ClassInfoConstraintFunction::IsInstance => {
Type::instance(db, class.default_specialization(db))
}
ClassInfoConstraintFunction::IsSubclass => {
SubclassOfType::from(db, class.default_specialization(db))
}
};
match classinfo {
@ -186,13 +190,70 @@ impl ClassInfoConstraintFunction {
if class_literal.is_known(db, KnownClass::Any) {
None
} else {
Some(constraint_fn(class_literal.default_specialization(db)))
Some(constraint_fn(class_literal))
}
}
Type::SubclassOf(subclass_of_ty) => {
subclass_of_ty.subclass_of().into_class().map(constraint_fn)
Type::SubclassOf(subclass_of_ty) => match subclass_of_ty.subclass_of() {
SubclassOfInner::Class(ClassType::NonGeneric(class)) => Some(constraint_fn(class)),
// It's not valid to use a generic alias as the second argument to `isinstance()` or `issubclass()`,
// e.g. `isinstance(x, list[int])` fails at runtime.
SubclassOfInner::Class(ClassType::Generic(_)) => None,
SubclassOfInner::Dynamic(dynamic) => Some(Type::Dynamic(dynamic)),
},
Type::Dynamic(_) => Some(classinfo),
Type::Intersection(intersection) => {
if intersection.negative(db).is_empty() {
let mut builder = IntersectionBuilder::new(db);
for element in intersection.positive(db) {
builder = builder.add_positive(self.generate_constraint(db, *element)?);
}
Some(builder.build())
} else {
// TODO: can we do better here?
None
}
}
_ => None,
Type::Union(union) => {
let mut builder = UnionBuilder::new(db);
for element in union.elements(db) {
builder = builder.add(self.generate_constraint(db, *element)?);
}
Some(builder.build())
}
Type::TypeVar(type_var) => match type_var.bound_or_constraints(db)? {
TypeVarBoundOrConstraints::UpperBound(bound) => self.generate_constraint(db, bound),
TypeVarBoundOrConstraints::Constraints(constraints) => {
self.generate_constraint(db, Type::Union(constraints))
}
},
// It's not valid to use a generic alias as the second argument to `isinstance()` or `issubclass()`,
// e.g. `isinstance(x, list[int])` fails at runtime.
Type::GenericAlias(_) => None,
Type::AlwaysFalsy
| Type::AlwaysTruthy
| Type::BooleanLiteral(_)
| Type::BoundMethod(_)
| Type::BoundSuper(_)
| Type::BytesLiteral(_)
| Type::Callable(_)
| Type::DataclassDecorator(_)
| Type::Never
| Type::MethodWrapper(_)
| Type::ModuleLiteral(_)
| Type::FunctionLiteral(_)
| Type::ProtocolInstance(_)
| Type::PropertyInstance(_)
| Type::SpecialForm(_)
| Type::NominalInstance(_)
| Type::LiteralString
| Type::StringLiteral(_)
| Type::IntLiteral(_)
| Type::KnownInstance(_)
| Type::TypeIs(_)
| Type::WrapperDescriptor(_)
| Type::DataclassTransformer(_) => None,
}
}
}