Does it use WasmGC, or bundle its own garbage collector?
I think WasmGC is very hard to make work with laziness. A lazy value is always a closure on the heap. If an expression might be unused, throw a closure which computes it on the heap If the value is actually needed, invoke the closure. Optionally replace the closure with a black hole. A black hole is just a closure which pauses any thread which calls it, to be resumed once the first thread finishes with the expression…
> Anyway, iirc WasmGC wants very rigid types without dynamic type changes.
You can have dynamic type changes in the current WasmGC MVP, but they are modeled as explicit downcasts from a supertype of some sort. There's not even any express support for tagged unions, structs and downcasting is all you get at the moment.