1 // { dg-module-do run } 2 // { dg-additional-options -fmodule-header } 3 4 template<template<typename> class _Op> 5 using __detected_or_t = long; 6 7 template<typename _Ptr> 8 struct pointer_traits 9 { 10 template<typename _Tp> 11 using __difference_type = typename _Tp::difference_type; 12 13 using difference_type = __detected_or_t<__difference_type>; 14 }; 15 16