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[easy] Fix runtime checkable protocol unsafe overlap with inheritance test case #1695

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[easy] Fix runtime checkable protocol unsafe overlap with inheritance test case #1695

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[easy] Fix runtime checkable protocol unsafe overlap with inheritance…
fangyi-zhou Nov 26, 2025
1612039
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fangyi-zhou Nov 26, 2025
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38 changes: 22 additions & 16 deletions pyrefly/lib/alt/special_calls.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -372,6 +372,7 @@ impl<'a, Ans: LookupAnswer> AnswersSolver<'a, Ans> {
// fresh vars and solve them during the is_subset_eq check below.
let protocol_instance_ty = self.instantiate_fresh_class(cls);
if let Some(object_type) = &object_type {
let mut unsafe_overlap_errors = vec![];
for field_name in &protocol_metadata.members {
if !self.has_attr(object_type, field_name) {
// It's okay if the field is missing, since
Expand All @@ -395,24 +396,29 @@ impl<'a, Ans: LookupAnswer> AnswersSolver<'a, Ans> {
"runtime_checkable_protocol_unsafe_overlap",
);
if !self.is_subset_eq(&field_ty, &protocol_field_ty) {
errors.add(
range,
ErrorInfo::Kind(ErrorKind::InvalidArgument),
vec1![
format!(
"Runtime checkable protocol `{}` has an unsafe overlap with type `{}`",
cls.name(),
self.for_display(object_type.clone())
),
format!(
"Attribute `{}` has incompatible types: expected `{}`, got `{}`",
field_name,
self.for_display(protocol_field_ty),
self.for_display(field_ty),
),
]);
unsafe_overlap_errors.push(
format!(
"Attribute `{}` has incompatible types: expected `{}`, got `{}`",
field_name,
self.for_display(protocol_field_ty),
self.for_display(field_ty),
),
);
}
}
if !unsafe_overlap_errors.is_empty() {
let mut full_msg = vec1![format!(
"Runtime checkable protocol `{}` has an unsafe overlap with type `{}`",
cls.name(),
self.for_display(object_type.clone())
)];
full_msg.extend(unsafe_overlap_errors);
errors.add(
range,
ErrorInfo::Kind(ErrorKind::InvalidArgument),
full_msg,
);
}
}
}
}
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9 changes: 4 additions & 5 deletions pyrefly/lib/test/protocol.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -668,23 +668,22 @@ issubclass(No, UnsafeProtocol) # E: Runtime checkable protocol `UnsafeProtocol`
);

testcase!(
bug = "@runtime_checkable doesn't propagate through inheritance",
test_runtime_checkable_unsafe_overlap_with_inheritance,
r#"
from typing import Protocol, runtime_checkable
@runtime_checkable
class UnsafeProtocol(Protocol):
def foo(self) -> int: ...
@runtime_checkable # E: @runtime_checkable can only be applied to Protocol classes
class ChildUnsafeProtocol(UnsafeProtocol):
@runtime_checkable
class ChildUnsafeProtocol(UnsafeProtocol, Protocol):
def bar(self) -> str: ...
class No:
def foo(self) -> str:
return "not an int"
def bar(self) -> int:
return 42
isinstance(No(), ChildUnsafeProtocol)
issubclass(No, ChildUnsafeProtocol)
isinstance(No(), ChildUnsafeProtocol) # E: Runtime checkable protocol `ChildUnsafeProtocol` has an unsafe overlap with type `No`
issubclass(No, ChildUnsafeProtocol) # E: Runtime checkable protocol `ChildUnsafeProtocol` has an unsafe overlap with type `No`
"#,
);

Expand Down