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[ty] Ban protocols from inheriting from non-protocol generic classes (#19941)

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Alex Waygood 2025-08-16 19:38:43 +01:00 • committed by GitHub
parent f4d8826428
commit 9ac39cee98
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2 changed files with 15 additions and 10 deletions
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8
crates/ty_python_semantic/resources/mdtest/protocols.md
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@ -150,6 +150,14 @@ class AlsoInvalid(MyProtocol, OtherProtocol, NotAProtocol, Protocol): ...
# revealed: tuple[<class 'AlsoInvalid'>, <class 'MyProtocol'>, <class 'OtherProtocol'>, <class 'NotAProtocol'>, typing.Protocol, typing.Generic, <class 'object'>] # revealed: tuple[<class 'AlsoInvalid'>, <class 'MyProtocol'>, <class 'OtherProtocol'>, <class 'NotAProtocol'>, typing.Protocol, typing.Generic, <class 'object'>]
reveal_type(AlsoInvalid.__mro__) reveal_type(AlsoInvalid.__mro__)
class NotAGenericProtocol[T]: ...
# error: [invalid-protocol] "Protocol class `StillInvalid` cannot inherit from non-protocol class `NotAGenericProtocol`"
class StillInvalid(NotAGenericProtocol[int], Protocol): ...
# revealed: tuple[<class 'StillInvalid'>, <class 'NotAGenericProtocol[int]'>, typing.Protocol, typing.Generic, <class 'object'>]
reveal_type(StillInvalid.__mro__)
``` ```
But two exceptions to this rule are `object` and `Generic`: But two exceptions to this rule are `object` and `Generic`:

17
crates/ty_python_semantic/src/types/infer.rs
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@ -1117,13 +1117,6 @@ impl<'db, 'ast> TypeInferenceBuilder<'db, 'ast> {
// - Check for inheritance from a `@final` classes // - Check for inheritance from a `@final` classes
// - If the class is a protocol class: check for inheritance from a non-protocol class // - If the class is a protocol class: check for inheritance from a non-protocol class
for (i, base_class) in class.explicit_bases(self.db()).iter().enumerate() { for (i, base_class) in class.explicit_bases(self.db()).iter().enumerate() {
if let Some((class, solid_base)) = base_class
.to_class_type(self.db())
.and_then(|class| Some((class, class.nearest_solid_base(self.db())?)))
{
solid_bases.insert(solid_base, i, class.class_literal(self.db()).0);
}
let base_class = match base_class { let base_class = match base_class {
Type::SpecialForm(SpecialFormType::Generic) => { Type::SpecialForm(SpecialFormType::Generic) => {
if let Some(builder) = self if let Some(builder) = self
@ -1155,13 +1148,17 @@ impl<'db, 'ast> TypeInferenceBuilder<'db, 'ast> {
); );
continue; continue;
} }
Type::ClassLiteral(class) => class, Type::ClassLiteral(class) => ClassType::NonGeneric(*class),
// dynamic/unknown bases are never `@final` Type::GenericAlias(class) => ClassType::Generic(*class),
_ => continue, _ => continue,
}; };
if let Some(solid_base) = base_class.nearest_solid_base(self.db()) {
solid_bases.insert(solid_base, i, base_class.class_literal(self.db()).0);
}
if is_protocol if is_protocol
&& !(base_class.is_protocol(self.db()) && !(base_class.class_literal(self.db()).0.is_protocol(self.db())
|| base_class.is_known(self.db(), KnownClass::Object)) || base_class.is_known(self.db(), KnownClass::Object))
{ {
if let Some(builder) = self if let Some(builder) = self