*sigh*

gistfile1.txt

Original:
public enum EnumTest {
    ONE() { {
        System.out.println("ONE");
    } },
    TWO() { {
        System.out.println("TWO");
    } };
}

Fernflower:
<CRASH>: 0 byte file EnumTest

Procyon:
public enum EnumTest
{
    ONE,
    TWO;
}

CFR:
public enum EnumTest {
{
    ONE{
    }
    ,
    TWO{
    };
    

    private EnumTest(String string2, int string2) {
    }

    /* synthetic */ EnumTest(String string22, int string22, EnumTest string22) {
        int n;
        EnumTest enumTest;
        String string3;
        enumTest(string3, n);
    }

}