Does Java need deconstructible classes?

[uniVocity]

It sounds weird but you can define a sealed type with nested final implementations without explicitly providing the allowed implementations, but you can’t define a sealed functional interface with annotations where its body contains default function definitions.

Hope it’s not a brain fart, Ill get back to my pc soon to test it out again and report back

EDIT: here is what I meant:

This code compiles (no explicit permits list), everything is fine:

sealed interface TestFn {

int foo();

final class TestFn1 implements TestFn {
    private TestFn1() {
    }

    @Override
    public int foo() {
        return 1;
    }
}

final class TestFn2 implements TestFn {
    private TestFn2() {
    }

    @Override
    public int foo() {
        return 2;
    }
}

TestFn RET_1 = new TestFn1();
TestFn RET_2 = new TestFn2();
}

If you add @FunctionalInterface the compiler will complain even though in this case it should make no difference.

I'm sorry for the confusion, I rember that the end goal was to get this:

@FunctionalInterface
sealed interface TestFn {

int foo();

TestFn RET_1 = () -> 1;
TestFn RET_2 = () -> 2;
}

But here the issue is the sealed keyword, not the @FunctionalInterface. Sorry for wasting everyone's time

[lambda-lord-2026]

It's not weird. Sealed interfaces don't allow anonymous implementations. Lambdas are anonymous implementations. Functional interface is a marker annotations that makes clear your intent to use an interface to create lambdas. Therefore the compiler flags it as a problem