Question about thread-local function optimization

Per the explainer, thread-local WA.Function starts as null on all threads and then transitions to non-null exactly once on a thread when the initialize method is called.

As an engine-internal optimization, setting a thread-local global to a thread-local function wrapper can skip a layer of indirection and set the global to refer directly to the bound function, since it will never change or be observed from another thread. This optimization only works because the dynamic contexts of thread-local globals and thread-local function wrappers are the same, i.e. an entire thread or agent.

How can the above be possible? When the global.set for a thread-local global happens, the initialize method may not have happened yet. From core wasm's perspective this is a non-null (ref func shared), so I don't think we can say that it traps due to null or type mismatch.

Read the explainer section describing thread-local WA.Function and the engine-internal optimization. Trace the interaction between initialize, global.set, nullability, and (ref func shared) in core WebAssembly. Done means resolving whether the optimization can be valid before initialize, with the proposal text or semantics clarified.