Looking at these, we could put Compact, Uint, Vec, Tuple, Struct etc as abstract classes, and enforce the usage .with() which will create a real class

Throwing ideas again, an alternative syntax would be new Compact.with(registry.BlockNumber), on in general new (api.)registry.BlockNumber('234')

I would prefer them to be used that way, yes. Probably after #1518 (which has it's own issues, but opens the way for removing the U{8,16,32,64,128,256} classes (and allows stuff like U2048)

Could we do const registry = new TypeRegistry(meta: string) (string being rpc). This way we could remove setMetadata from Metadata's constructor, and make it private.

hmm, maybe not, because Metadata needs registry already

So the above is only in tests - and it is a bit of magic, as per the comment suppression. I was thinking about doing that, but it actually only helps in tests - in the Api itself the registry is created right-up-front before we even have metadata, so we still need to inject or call setMetadata (Originally I have an explicit set, now metadata does it).

Your approach may be cleaner, at least for "it not just doing stuff" and will certainly clean up the tests.

Still creates a small issue in the Decorated tests, but can call setMetadata there explicitly like we have in the Api then. Ok, will follow the meta?: string | Uint8Array and see where it gets us.

On second thought... this gets back into circular dep hell again. (Which is why the RegistryMetadata was introduced, it is a real mess without it with left-and-right breakages)

Yeah, actually I don't think metadata should go inside registry. Ideally, I would see a class Context which has this interface:

constructor(registry: Registry, metadata?: Metadata);
registry: Registry;
metadata?: Metadata;
setMetadata: (meta: string|u8a);

In tests that don't need metadata, we just new Context. In tests with calls/events, we do an additional context.setMetadata()

Edit: So it's actually pretty similar to current architecture. Would just probably remove setMetadata from Metadata constructor, and put it more explicitly everywhere.