Technically speaking, that's not `Base + IFace`, b...

# language-proposals

[dmitry.petrov]

Technically speaking, that's not Base + IFace, but Base & IFace. That is, an intersection of Base and IFace.
When you have class C : A, B, it means C <: A & B, not C <: A + B.
We are working on a new TI (for more than a year...) that will handle intersection types better.
Then, probably, we might provide better support for intersection types.