public static interface DistExecutor.SafeReferent
DistExecutor.callWhenOn(Dist, Supplier)
above.
SafeReferents assert that they are defined as a separate method outside the scope of the calling class.
Implementations need to be defined in a separate class to the referring site, with appropriate
visibility to be accessible at the callsite (generally, avoid private methods).
Valid:
DistExecutor.safeCallWhenOn(Dist.CLIENT, ()->AnotherClass::clientOnlyMethod);
Invalid:
DistExecutor.safeCallWhenOn(Dist.CLIENT, ()->()->Minecraft.getInstance().world);