[Sealed types] Proper sealing of hierarchy rejected in incremental builds if permitted class is generic

[konczdev]

The compiler incorrectly reports that a generic class is not a permitted subtype in a sealed class hierarchy, even when it's explicitly listed in the permits clause.

Minimal example to reproduce:

public sealed abstract class Message permits Request {
    private final String id;
    
    protected Message(String id) {
        this.id = id;
    }
}

public final class Request<T> extends Message {  // Error here
    private final T payload;
    
    public Request(String id, T payload) {
        super(id);
        this.payload = payload;
    }
}

Expected behavior:

• The code should compile since Request is explicitly listed in Message's permits clause
• The addition of generic type parameters should not affect the sealed class hierarchy

Actual behavior:

• Compiler error: "The class Request cannot extend the class Message as it is not a permitted subtype of Message"
• Removing the generic type parameter makes the error disappear

This appears to be a bug in handling generic type parameters within sealed class hierarchies.

Java version: 17 (Eclipse Temurin jdk-17.0.11+9)

Eclipse IDE for Eclipse Committers (includes Incubating components)

Version: 2024-12 (4.34.0)
Build id: 20241128-0757

[srikanth-sankaran]

This appears to be a bug in handling generic type parameters within sealed class hierarchies.

Java version: 17 (Eclipse Temurin jdk-17.0.11+9)

Eclipse IDE for Eclipse Committers (includes Incubating components)

Version: 2024-12 (4.34.0) Build id: 20241128-0757

I don't think these version numbers look right.

This problem is not reproducible on Eclipse SDK 4.33 or 4.34 or on master/HEAD.

I intend to close this as not reproducible.

It is likely the Temurin build is using an ancient version of JDT plugins.

[konczdev]

@srikanth-sankaran
Here is a freshly downloaded Eclipse IDE for Java Developers

[konczdev]

JDT plugin versions:

[konczdev]

@srikanth-sankaran I made an observation: if I clean the project the error is gone until I touch the affected file and save. After saving the error shows.

[srikanth-sankaran]

@srikanth-sankaran I made an observation: if I clean the project the error is gone until I touch the affected file and save. After saving the error shows.

Thanks for that tip - reproduced. Looks like a defect in incremental building. Investigating ...

[srikanth-sankaran]

Works fine in 3.43. Mea cupla :-(

[konczdev]

Thank you!