Wrapping nested templated types in nim

Question

I have a C++ type like:

template <typename T>
class Vector {
  struct Iterator {
  };
};

And in C++ I can use Iterator as Vector<int>::Iterator.

How do I wrap this to use it from Nim? c2nim emits

type Vector[T] {.importcpp...} = object
  type Iterator[T] {.importcpp...}

which doesn't compile because nim doesn't have nested types, and would produce Vector<T>::Iterator<T> rather than Vector<T>::Iterator.

I can use non-nested types in Nim:

type VectorIterator[T] {.importcpp: "Vector::Iterator".}
var v : VectorIterator[cint]

And this naturally produces Vector::Iterator<int>, which is wrong (it should be Vector<int>::Iterator).

Is there a way to change the import specification to produce the correct output?

Answer 1

I've recently added the support for wrapping such nested types in the compiler. You'll need to use the latest code from the devel branch. Here is how it can be done:

{.emit: """

template <class T>
struct Vector {
  struct Iterator {};
};

""".}

type
  Vector {.importcpp: "Vector".} [T] = object
  VectorIterator {.importcpp: "Vector<'0>::Iterator".} [T] = object

var it: VectorIterator[int]

The relevant details in the manual can be found here and here.