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fix report unsafe __get__ return types #1317

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172 changes: 172 additions & 0 deletions pyrefly/lib/alt/class/class_field.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -31,6 +31,7 @@ use ruff_python_ast::name::Name;
use ruff_text_size::TextRange;
use starlark_map::small_map::SmallMap;
use starlark_map::small_set::SmallSet;
use vec1::Vec1;
use vec1::vec1;

use crate::alt::answers::LookupAnswer;
Expand Down Expand Up @@ -1264,6 +1265,7 @@ impl<'a, Ans: LookupAnswer> AnswersSolver<'a, Ans> {
} else {
value_ty
};
let descriptor_value_ty = value_ty.clone();

// Types provided in annotations shadow inferred types
let ty = if let Some(ann) = annotation {
Expand Down Expand Up @@ -1329,6 +1331,17 @@ impl<'a, Ans: LookupAnswer> AnswersSolver<'a, Ans> {
ty
};

if descriptor.is_some() {
self.validate_descriptor_annotation(
class,
name,
annotation,
&descriptor_value_ty,
range,
errors,
);
}

// Pin any vars in the type: leaking a var in a class field is particularly
// likely to lead to data races where downstream uses can pin inconsistently.
//
Expand Down Expand Up @@ -1470,6 +1483,165 @@ impl<'a, Ans: LookupAnswer> AnswersSolver<'a, Ans> {
None
}

fn collect_descriptor_classes_from_type(&self, out: &mut SmallSet<ClassType>, ty: &Type) {
match ty {
Type::ClassType(cls) => {
out.insert(cls.clone());
}
Type::Union(types) => {
for ty in types {
self.collect_descriptor_classes_from_type(out, ty);
}
}
_ => {}
}
}

fn descriptor_info_from_class(&self, cls: ClassType, range: TextRange) -> Option<Descriptor> {
let getter = self
.get_class_member(cls.class_object(), &dunder::GET)
.is_some();
let setter = self
.get_class_member(cls.class_object(), &dunder::SET)
.is_some();
if getter || setter {
Some(Descriptor {
range,
cls,
getter,
setter,
})
} else {
None
}
}

fn validate_descriptor_annotation(
&self,
class: &Class,
name: &Name,
annotation: Option<&Annotation>,
value_ty: &Type,
range: TextRange,
errors: &ErrorCollector,
) {
let Some(annotation) = annotation else {
return;
};
let expected_ty = annotation.get_type().clone();
if expected_ty.is_any() || expected_ty.is_error() {
return;
}

let mut descriptor_classes = SmallSet::new();
self.collect_descriptor_classes_from_type(&mut descriptor_classes, value_ty);

if descriptor_classes.is_empty() {
return;
}

let class_type = self.as_class_type_unchecked(class);
let mut messages = Vec::new();
let ignore_errors = self.error_swallower();

for cls in descriptor_classes {
if let Type::ClassType(expected_cls) = &expected_ty
&& expected_cls.class_object() == cls.class_object()
{
continue;
}
let Some(desc_info) = self.descriptor_info_from_class(cls.clone(), range) else {
continue;
};

if desc_info.getter {
if let Some(getter_method) =
self.resolve_descriptor_getter(&desc_info, &ignore_errors)
{
let instance_ret = self.call_descriptor_getter(
getter_method.clone(),
DescriptorBase::Instance(class_type.clone()),
range,
&ignore_errors,
None,
);
if !self.is_subset_eq(&instance_ret, &expected_ty) {
let actual_display = self
.for_display(instance_ret.deterministic_printing())
.deterministic_printing();
let expected_display = self
.for_display(expected_ty.clone().deterministic_printing())
.deterministic_printing();
messages.push(format!(
"Descriptor `{}` returns `{}` when accessed on instances of `{}`, which is not assignable to `{}`",
name,
actual_display,
class.name(),
expected_display,
));
}

let class_ret = self.call_descriptor_getter(
getter_method,
DescriptorBase::ClassDef(class.dupe()),
range,
&ignore_errors,
None,
);
if !self.is_subset_eq(&class_ret, &expected_ty) {
let actual_display = self
.for_display(class_ret.deterministic_printing())
.deterministic_printing();
let expected_display = self
.for_display(expected_ty.clone().deterministic_printing())
.deterministic_printing();
messages.push(format!(
"Descriptor `{}` returns `{}` when accessed on class `{}`, which is not assignable to `{}`",
name,
actual_display,
class.name(),
expected_display,
));
}
}
}

if desc_info.setter {
if let Some(setter_method) =
self.resolve_descriptor_setter(&desc_info, &ignore_errors)
{
let setter_check_errors = self.error_collector();
self.call_descriptor_setter(
setter_method.clone(),
class_type.clone(),
CallArg::ty(&expected_ty, range),
range,
&setter_check_errors,
None,
);
if !setter_check_errors.is_empty() {
let setter_display = self
.for_display(setter_method.deterministic_printing())
.deterministic_printing();
let expected_display = self
.for_display(expected_ty.clone().deterministic_printing())
.deterministic_printing();
messages.push(format!(
"Descriptor `{}` setter `{}` does not accept annotated type `{}`",
name, setter_display, expected_display,
));
}
}
}
}

if !messages.is_empty() {
if let Ok(msgs) = Vec1::try_from_vec(messages) {
errors.add(range, ErrorInfo::Kind(ErrorKind::BadAssignment), msgs);
}
}
}

/// Return (type of first inherited field, first inherited annotation). May not be from the same class!
/// For example, in:
/// class A:
Expand Down
26 changes: 26 additions & 0 deletions pyrefly/lib/test/descriptors.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -319,3 +319,29 @@ class A:
return self.d
"#,
);

testcase!(
test_descriptor_incompatible_get_return_annotation,
r#"
from typing import Literal
class A:
def __get__(self, obj, objtype) -> A | int: ...
class B(A):
def __get__(self, obj, objtype) -> Literal[1]: ...
class C:
a: A = B() # E: Descriptor `a` returns `Literal[1]` when accessed on instances of `C`, which is not assignable to `A`
"#,
);

testcase!(
test_descriptor_incompatible_set_annotation,
r#"
from typing import Any
class A:
def __set__(self, obj, value: Any) -> None: ...
class B(A):
def __set__(self, obj, value: str) -> None: ...
class C:
a: A = B() # E: Descriptor `a` setter `BoundMethod[B, (self: B, obj: Unknown, value: str) -> None]` does not accept annotated type `A`
"#,
);