Creating interfaces in different namespaces

I implemented a type inference algorithm and ran into some difficulty trying to figure out how to define interfaces outside of the ::mlir parent namespace. I spent some cursory time trying to decide if I was just holding it wrong and thought I’d ask before digging in deeper.

Here are my interfaces:

When I just had a type interface (thanks @River707 – it works beautifully), I could put it in whatever wrapping namespace I wanted and make sure that in the C++ type declaration, I just referenced the right fully qualified name.

However, when I added an op interface and attempted to use it from Tablegen, it blew up in every combination I tried (except for putting it in the outer ::mlir namespace). I couldn’t find a combination of interface name and cppClassName that both compiled properly and could be referenced from an DeclareOpInterfaceMethods template (one or the other was always doing something illegal with a fully-qualified class name).

Am I in uncharted territory here, or has someone managed to make this work?

I think you’re right: it doesn’t work. This has been bugging me fur a while but I haven’t had a chance to look into it.

It is a combination of unfinished discussion about convention and nobody really being too constrained by it (e.g., a couple of using statements did the job and folks working together meant overlapping concepts at the name level gets disambiguated and deduped).

It’s been a while but I don’t think it’s very hard coded (native trait needing to be in a specific namespace comes to mind) in the generator/code side. But then also code changes will be the smaller part here.

Understood - it’s not likely to be a huge problem for interfaces that are part of MLIR itself but is definitely annoying for those outside. Not sure when/if I’ll get to straightening it out, since I’d like to keep elaborating what I’m working on and the hack of putting them in the mlir root namespace works.

Should likely be fixed by https://reviews.llvm.org/D83604.

Excellent! Thank you, River!