[The-Alchemist]

Motivation

A language sometimes needs a reference constant operand whose value is null, for example an optional type or a missing default. ConstantsBuffer.add(null) threw NullPointerException because it started with Objects.requireNonNull. Serialization already records null with CODE_$CREATE_NULL, but the builder rejected the value before it reached the pool.

addNull() is not a substitute. Its reserved slots are meant to be patched after materialization, and each call allocates a new slot. Using it for a real null constant grows the pool and can later alias a patched value. We've worked around the rejection in our Cloffle project with a sentinel value instead of passing null.

Summary

• Reference constant operands may be null. ConstantsBuffer.add(null) stores that null in one shared constant-pool slot.
• addNull() still reserves a distinct empty slot on each call so the slot can be patched after materialization.
• LoadConstant still rejects null; use LoadNull for a null dynamic value. Local accessors still reject null.