Hmm, what do you mean? Haskell is generally considered nominally typed (or rather types introduced by its newtype and data declarations are ...). "Structural typing" typically refers to things like polymorphic row types and polymorphic variants.

Sure, my mistake. I meant something looser.

Only that the types can be analysed structurally (ie., pattern matched).

In C++, etc. there's a "radical nominalism" in which the type was very opaque, ie., encapsualated.

It is complicated. Templates do allow some form of structural typing and the new-in-C++17 structured bindings do allow for decomposing and inspecting types (although this being C++ it is kind of awkward). Structured bindings are expected to evolve into full pattern matching in the future.