This reverts commit 12512076.

class java.lang.NullPointerException: null
java.util.Objects.requireNonNull(Objects.java:203)
java.util.Optional.<init>(Optional.java:96)
java.util.Optional.of(Optional.java:108)
org.aminb.alloy.catalyst.SSRVisitor.putCandidateIfAbsent(SSRVisitor.java:52)
…

I don’t know why I even try with Java…