This module deals with imports of nested modules (import submodule). This is more complex than it might seem at first because to resolve a declaration like import submodule X we need to resolve what X referes to before we know what it will import.

Even triciker is the case for functor instantiations:

module M = F { X } import M

In this case, even if we know what M referes to, we first need to resolve F, so that we can generate the instantiation and generate fresh names for names defined by M.

If we want to support applicative semantics, then before instantiation M we also need to resolve X so that we know if this instantiation has already been generated.

An overall guiding principle of the design is that we assume that declarations can be ordered in dependency order, and submodules can be processed one at a time. In particular, this does not allow recursion across modules, or functor instantiations depending on their arguments.

Thus, the following is OK:

module A where x = 0x2

submodule B where y = x

z = B::y

However, this is not OK:

submodule A = F X submodule F where import A