disallow import root during validation

[Conduitry]

That the root context is called root is ingrained pretty deeply, and it seems difficult to deconflict this with an import of root. So for now it's probably best to simply disallow this entirely during validation.

[Rich-Harris]

This seems like a good precaution. Is there any place where generated code would come into contact with that though? root is only ever a parameter in generated code, so it shouldn't matter if it shadows an import since that's only referenced inside the template IIFE, no?

[Conduitry]

Well this could come up if an import root was being used as a nested component. Then with the recent change to use imported components directly instead of via template.components, there would be a reference to that outside of the template IIFE. It's a bizarre case, and right now I can't think of another way it might come up.

[Rich-Harris]

Ah, of course. Forgot about that case.