Boost multi_index_container，按标签获取索引会导致编译器错误

Question

所以，我试图涉足 multi_index_container 并遇到一个相当奇怪的编译器错误，首先这里是演示我的问题的最简单的示例（我可能错过了一些愚蠢简单的东西）...

#include <boost/multi_index_container.hpp>
#include <boost/multi_index/sequenced_index.hpp>
#include <boost/multi_index/ordered_index.hpp>
#include <boost/multi_index/identity.hpp>
#include <boost/multi_index/mem_fun.hpp>

namespace multi_index = boost::multi_index;

template <typename _IdType>
class A
{
public:
  typedef _IdType IdType;
  IdType getId() const { return id; }

private:
  IdType id;
};

struct id_index{};

template <typename Traits>
class Container
{
  typedef typename Traits::AType AType;
  typedef typename AType::IdType IdType;

  typedef typename multi_index::multi_index_container<
    AType,
    multi_index::indexed_by<
      // sort by Id
      multi_index::ordered_non_unique<multi_index::tag<id_index>, BOOST_MULTI_INDEX_CONST_MEM_FUN(AType, IdType, getId) >
    >
  > ASet;

  typedef typename ASet::template index<id_index>::type::const_iterator a_it;
  typedef typename ASet::template index<id_index>::type::reverse_iterator a_rit;

  typedef typename ASet::template index<id_index>::type id_index_t;

public:

  bool addA(AType const& cA)
  {
    const id_index_t& os = _cSet.get<id_index>(); // line 1: errors occur here
    // .. do stuff
    return true;
  }

private:
  // Instance of the container...
  ASet _cSet;
};

struct ATraits
{
  typedef A<int> AType;
};

int main(void)
{
  Container<ATraits> container;

  ATraits::AType a;

  container.addA(a);

  return 0;
}

g++（gcc 4.4.4，linux）报告的错误是：

error: expected primary-expression before ‘>’ token (@ line 1)
error: expected primary-expression before ‘)’ token (@ line 1)

所以这工作正常，直到我将容器转换为类模板，在此之后，我收到此错误，并且无法弄清楚为什么......

任何想法都会受到赞赏...

Answer 1

  bool addA(AType const& cA)
  {
    const id_index_t& os = _cSet.template get<id_index>(); // line 1: errors occur here
    // .. do stuff
    return true;
  }