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From: "pinskia at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug c++/66153] Internal compiler error in nested template function
Date: Tue, 21 Dec 2021 21:29:55 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D66153

--- Comment #8 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Reduced further:
#include <type_traits>

template <class T> struct TypeMapper { static const int NestLevel =3D
T::NestLevel; };
template<> struct TypeMapper<double> { static const int NestLevel =3D 0; };
template<class obj> struct Container { obj data; };
template<class obj> struct Recursive {
  enum { NestLevel =3D TypeMapper<obj>::NestLevel + 1};
};
template<int N,class obj,  typename std::enable_if<N=3D=3Dobj::NestLevel >:=
:type *
=3D nullptr >
auto function(const obj &arg)-> obj
{
  return arg;
}
template<int N,class obj, typename std::enable_if<N!=3Dobj::NestLevel >::ty=
pe * =3D
nullptr >
  auto function(const obj &arg)-> obj
{
  return obj{};
}
template<int N,class obj>
  auto function(const Container<obj> & arg) ->
Container<decltype(function<N>(arg.data))>
{
  Container<Recursive<Recursive<double> > > ret;
  return ret;
}
int main(int argc,char **argv)
{
  Container<Recursive<Recursive<double> > > array;
  Container<Recursive<Recursive<double> > > ret;

  function<1>(array);
}

----- CUT -----
I have seen another one similar to this recently.=