https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88162
Bug ID: 88162
Summary: GCC does not accept non-type template parameters of
class type
Product: gcc
Version: 9.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: tiagomacarios at gmail dot com
Target Milestone: ---
Looking at http://eel.is/c++draft/temp.arg.nontype I would think that the code
below is C++17 complaint.
GCC thinks this is only available in 2a mode. clang compiles it fine in c++17
mode.
https://godbolt.org/z/PGoXwX
template<class T> struct id
{
using type = T;
};
template<auto X, template<auto> class T> id<decltype(X)> f( T<X> )
{
};
constexpr struct zero_type
{
template<class T> constexpr operator T () const { return {}; }
} zero;
template<template<auto> class T> using nttp_t = typename decltype( f(T<zero>())
)::type;
template <int> struct int_constant {};
template <char> struct char_constant {};
template <long> struct long_constant {};
template <void*> struct voidp_constant {};
void g( nttp_t<int_constant>, nttp_t<char_constant>, nttp_t<long_constant>,
nttp_t<voidp_constant> )
{
}
