[Bug c++/81232] New: compiler crashes for template function overload

[manish.baphna at citi dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81232

            Bug ID: 81232
           Summary: compiler crashes for template function overload
           Product: gcc
           Version: 6.1.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: manish.baphna at citi dot com
  Target Milestone: ---

Created attachment 41636
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=41636&action=edit
diagnostic output from compiler

I am trying to use template function overloads and in a specific case, I was
expecting to deploy 'best match' overload but that somehow is not happening.
Template type deduction there is not matching 'best match' and compiler is
crashing(gcc6.1). Explicitly specifying types is helping here. Check main for
both versions of my usage. At this moment I am not sure if it's issue with gcc
or with my assumptions. Here is code

#include <iostream>
#include <type_traits>

using namespace std;

template <int N>
using int_ = integral_constant<int,N>;

struct Meta
{
    template<int N, typename T> static constexpr T ipow(T x)
    {
        return ipow<N, T>(x, int_<(N < 0) ? -1 : N>());
    }

    template<int N, typename T> static constexpr T ipow(T x, int_<-1>)
    {
        return static_cast<T>(1) / ipow<-N>(x, int_<-N>());
    }

    template<int N, typename T> static constexpr T ipow(T x, int_<N>)
    {
        return x * ipow<N-1>(x, int_<N-1>());
    }

    template<int N, typename T> static constexpr T ipow(T x, int_<0>)
    {
        return 1;
    }
};


int main(){
        Meta m1;
        cout << m1.ipow<-1, int>(2, int_<-1>()) << endl; // This works fine 
        cout << m1.ipow(2, int_<-1>()) << endl;      // This crashes compiler
}