Serialization requires an instance of the serializer, which cannot be obtained with the passed interface, abstract or sealed class.
Therefore, the specifying of such classes in `Serializable` annotation must be prohibited.
Fixes https://github.com/Kotlin/kotlinx.serialization/issues/2173
Relates #KT-58036
Merge-request: KT-MR-10753
Merged-by: Sergey Shanshin <Sergey.Shanshin@jetbrains.com>
Now annotations are resolved with following algorithm:
1. On COMPILER_REQUIRED_ANNOTATIONS we resolve all annotations
and store results if this is compiler annotation, plugin annotation,
or annotation with meta-annotation (meta annotations are checked
recursively with designated resolution if needed)
2. On TYPES stage we resolve all those annotations once again and if
some annotation changes resolution then we keep type from p.1 and
report error on this annotation, so user should disambiguate it
Ambiguity may occur because of nested annotations with same name as
plugin annotations:
```
annotation class SomeAnnotation // (1) plugin annotation
open class Base {
annotation class SomeAnnotation // (2)
}
class Derived : Base() {
@SomeAnnotation // <-----------------
class Inner
}
```
At COMPILER_REQUIRED_ANNOTATIONS annotation call will be resolved to (1)
because at this stage supertypes are not resolved yet, and we consider
only importing scopes. At the TYPES stage we will find correct
annotation from supertype
K2 plugin API has a limitation that meta annotations from plugin predicates
can't be used on nested annotations because their resolve process includes supertypes
resolve, that can be affected by the plugin itself. Therefore, @MetaSerializable
can't be applied to nested annotation classes in K2, which is reflected by
this diagnostic.
For old FE, diagnostic is lowered to WARNING with deprecation message.
Dmitrii Gridin