The two calls of Array.newInstance will return primitive array types if this.type represents a primitive type. The unchecked casts to T[] (erased to Object[]) will subsequently fail.

This issue is most likely academic, since the intended types for T will be functional interface types, but the issue exists in theory.

I suggest checking whether the backing type is primitive in the constructor (via Class#isPrimitive) and throwing IllegalArgumentException if that is the case.

Well, to really create this, you need extremely edgy code like this:

Event<Integer> event = EventFactory.createArrayBacked(int.class/* or Integer.TYPE */, invokers -> {
  /* computes and return an integer, who the heck knows how it's calculated*/
});

Meanwhile, this works:

Event<Integer> event = EventFactory.createArrayBacked(Integer.class, invokers -> {
  /* computes and return an integer, who the heck knows how it's calculated*/
});

This is really a non-issue.

EventFactory.createArrayBacked(int.class, intArray -> 0);

is enough to crash. This will be solved by #1369 anyway.

With #1369 merged, this will now cause a crash in the event ctor... Good enough imo.