[Boost-users] [Type Erasure] Ambiguous call with vs 2015 community

Subject: [Boost-users] [Type Erasure] Ambiguous call with vs 2015 community
From: Yuan Yao (yaoyuan0123_at_[hidden])
Date: 2015-08-31 06:53:35

Dear all,

I try to use type erasure on the free function foo. However, VS 2015 
failed to compile the following code, which is OK with GCC and CLang.

=========================================================
#include <boost/type_erasure/any.hpp>
#include <boost/type_erasure/free.hpp>
#include <typeindex>

std::type_index foo(int);

BOOST_TYPE_ERASURE_FREE((HasGetField), foo, 1)

using Type = boost::type_erasure::any<
     HasGetField<std::type_index(boost::type_erasure::_self const&)>,
     boost::type_erasure::_self const&
 >;

std::type_index foo(int) {
     return typeid(int);
}

int main() {
     Type x{ 1 };
     foo(x);

     return 0;
}

=========================================================

Source.cpp
C:\Program Files\Microsoft Visual Studio 14.0\VC\INCLUDE\xlocale(341): 
warning C4530: C++ exception handler used, but unwind semantics are not 
enabled. Specify /EHsc
Source.cpp(20): error C2668: 'boost::type_erasure::injectHasGetField<R 
(const boost::type_erasure::_self 
&),Base,boost::type_erasure::index_list<0>>::foo': ambiguous call to 
overloaded function
         with
         [
             R=std::type_index,
Base=boost::type_erasure::any_base<boost::type_erasure::any<HasGetField<std::type_index 
(const boost::type_erasure::_self &)>,boost::type_erasure::_self &&>>
         ]
Source.cpp(7): note: could be 'std::type_index 
boost::type_erasure::injectHasGetField<R (const 
boost::type_erasure::_self 
&),Base,boost::type_erasure::index_list<0>>::foo(eval_if_c<0,boost::type_erasure::detail::maybe_const_this_param<const 
boost::type_erasure::_self 
&,Base>,boost::type_erasure::as_param<Base,const 
boost::type_erasure::_self &>>::type)' [found using argument-dependent 
lookup]
         with
         [
             R=std::type_index,
Base=boost::type_erasure::any_base<boost::type_erasure::any<HasGetField<std::type_index 
(const boost::type_erasure::_self &)>,boost::type_erasure::_self &&>>
         ]
Source.cpp(7): note: or       'std::type_index 
boost::type_erasure::injectHasGetField<R (const 
boost::type_erasure::_self 
&),Base,boost::type_erasure::index_list<0>>::foo(eval_if_c<0,boost::type_erasure::detail::maybe_const_this_param<const 
boost::type_erasure::_self 
&,Base>,boost::type_erasure::as_param<Base,const 
boost::type_erasure::_self &>>::type)' [found using argument-dependent 
lookup]
         with
         [
             R=std::type_index,
Base=boost::type_erasure::any_base<boost::type_erasure::any<HasGetField<std::type_index 
(const boost::type_erasure::_self &)>,boost::type_erasure::_self &>>
         ]
Source.cpp(7): note: or       'std::type_index 
boost::type_erasure::injectHasGetField<R (const 
boost::type_erasure::_self 
&),Base,boost::type_erasure::index_list<0>>::foo(eval_if_c<0,boost::type_erasure::detail::maybe_const_this_param<const 
boost::type_erasure::_self 
&,Base>,boost::type_erasure::as_param<Base,const 
boost::type_erasure::_self &>>::type)' [found using argument-dependent 
lookup]
         with
         [
             R=std::type_index,
Base=boost::type_erasure::any_base<boost::type_erasure::any<HasGetField<std::type_index 
(const boost::type_erasure::_self &)>,boost::type_erasure::_self>>
         ]
Source.cpp(7): note: or       'std::type_index 
boost::type_erasure::injectHasGetField<R (const 
boost::type_erasure::_self 
&),Base,boost::type_erasure::index_list<0>>::foo(eval_if_c<0,boost::type_erasure::detail::maybe_const_this_param<const 
boost::type_erasure::_self 
&,Base>,boost::type_erasure::as_param<Base,const 
boost::type_erasure::_self &>>::type)' [found using argument-dependent 
lookup]
         with
         [
             R=std::type_index,
Base=boost::type_erasure::any_base<boost::type_erasure::any<HasGetField<std::type_index 
(const boost::type_erasure::_self &)>,const boost::type_erasure::_self &>>
         ]
Source.cpp(14): note: or       'std::type_index foo(int)'
Source.cpp(20): note: while trying to match the argument list '(Type)'

=========================================================

Moreover, I wonder whether the declaration is a must?

Thank you!