Unable to use EnumSet in JSweet 2

[joelmo]

I have this code that gives me this error, using EnumMap also gives a similar error:
ERROR: type 'Permission' does not satisfy the constraint 'Enum<Permission>' at src\shared\Service.java(7)

Here is the code.

Service.java:
package shared;

import java.util.EnumSet;

public interface Service {

    public void setPermissions(EnumSet<Permission> permissions);

}

...

Permission.java:
package shared;

public enum Permission {
    READ, WRITE
}

[lgrignon]

@joelmo Thanks for reporting. Not that easy to fix.
The quickest workaround would be to loosen the generic constraint here https://github.com/j4ts/j4ts/blob/master/src/main/java/java/util/EnumSet.java#L33 to avoid extends Enum if you want to give it a try

[joelmo]

I tried to find where that constraint is enforced in jsweet but didn't find where. The error message is confusing. Maybe jsweet doesn't translate enums into Enum<T?

[lgrignon]

That constraint is enforced by TypeScript compiler (tsc).
Indeed, it's specified in Java definition
public abstract class EnumSet<E extends Enum<E>> extends AbstractSet<E> {
Hence will be transpiled as a TS generic constraint.

The problem is that your enum is transpiled to a standard TS enum which does not extend Enum of course (not possible in TS by the way). I recommend you try with this contraint removed. It's not a major one.

That being said, it could be nice that JSweet deals with this specificity when using J4TS, but it would require a non negligible amount of work.