C++ map — Self referencing iterator

Question

Is there a way to declare a std::map whose value type is an iterator to itself?

map::iterator> myMap;
         


        

Answer 1

Only through type erasure. For example, you could use std::any

std::map myMap;
auto inserted = myMap.emplace("foo", std::any());

// how it can be populated:
inserted.first->second = inserted.first;
using it_type = decltype(myMap.begin());

// how values can be extracted:
auto it = std::any_cast(myMap["foo"]);

EDIT: The following also seems to work (clang-7.0.0 and gcc-8.2), but it is illegal (basically std::map does not specify that incomplete types are allowed):

struct Iter;
using Map = std::map;
struct Iter {
    Map::iterator it;
};