[Ibis] Add container and port operations

[mortbopet]

Adds: container, container instantiation, ports and port accesses.

Port access rules are implemented as:

• "local" port accesses (any port in the current or parent container hierarchy) can be accessed by a flat symbol name
• instance port accesses can be accessed by a nested symbol access.
• any instance in a parent container can be accessed.
• Only the top-level ports of the instance can be accessed (arbitrary restriction).

[teqdruid]

This is too general for my taste. Generality tends to introduce all sorts of corner cases. In my experience, it's better to be more restrictive at first then loosen those restrictions as necessary to support more use cases.

[mortbopet]

This is too general for my taste. Generality tends to introduce all sorts of corner cases. In my experience, it's better to be more restrictive at first then loosen those restrictions as necessary to support more use cases.

I can get behind having top-level modules continue to be classes, instead of everything a container - it simplifies some of the symbol definition search stuff. Port access functions (as previously discussed) i think have plenty of merit in being general. I think a compromise here is: classes as top level, no nested containers (=> no container instantiation), port-related ops as-is.

EDIT: Dipping my toes into the lowering now, and I think I've changed my mind - instance port accesses are semantically different enough from local port accesses to warrant a separate op.

[teqdruid]

Looks good! all my comments are minor.

[teqdruid]

This is a linear scan through the parentClass, right? If so, this is unacceptably inefficient longer term. Once we get the innerSym table stuff (on which I am pushing), it'll be more efficient. Please add a TODO comment reflecting this.

Also, doesn't the SymbolTable interface expose a method to do this?

[teqdruid]

I'm surprised you need to do the succeeded check separately.

[mortbopet]

FailureOr/LogicalResult is not and has never been implicitly convertible to bool.

[teqdruid]

Let's stick to the camelCase for instance names and CamelCase for class name convention. (I'm a hypocrite here since I never stick to any conventions, but do as I say not as I do! ;) )

[blakep-msft]

Beyond referencing ports in nested containers, I think we will need the ability to reference ports in parent/sibling containers. Something like a file system path like: ../../Foo/Bar/data. Will this code be able to be extended to support that?