gistfile1.txt

// C++
template<class T>
struct MyVector {
  using element_type = T;
  using iterator_type = T*; // or some trait.
  element_type operator[](unsigned i) { ... }
  iterator_type begin() { ... }
  iterator_type end() { ... }
};

// Imported as...
struct MyVector<T> {
  typealias element_type = T
  typealias iterator_type = // Either a pointer or through some importer magic we get an iterator. 
  func begin() -> iterator_type
  // You get the idea...
}

// Used as (before type checking)...
extension MyVector : VectorManualModel { ... }

func convertToSwiftArray<Vect: VectorManualModel>(_ vect: Vect) -> [Vect.ElementType] {
  var out = [Vect.ElementType]()
  var iter = vect.begin()
  let endIter = vect.end()
  while iter != endIter { out.append(iter.dereference()) iter = iter.next() }
  return out
}

func caller<Unrelated>(...) {
  let v: MyVector<Int> = ...
  convertToSwiftArray(v)
}

// After specialization...
struct __CxxSpecailzied_MyVector { ... }
func __CxxSpecialized_convertToSwiftArray(_ vec: MyVector<Int>) -> [Int] { ... }

func caller<Unrelated>(...) {
  let v: MyVector<Int> = ...
  __CxxSpecialized_convertToSwiftArray(v)
}