[Zababa]

I think that's structural. My understanding is the bound is based on structure, as there is no way to differentiate between a Summary + Display in a function and a Summary + Display in another. On the other hand, with Rust's enums (that are nominal), you can have enum A { Toto, Tata } and enum B { Toto, Tata }, and both with be different. A function accepting A will not accept B. A function accepting T : Summary + Display will accept any type that implements both traits.

From my understanding, nominal vs structural typing is about how you consider group of types. For structural typing, types that contain the same thing are the same. For nominal, that isn't the case.