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#include <type_traits>
#include <iostream>
 
struct my_abstract_class { virtual int x() = 0; };
struct my_incomplete_class;
 
template<typename T>
class is_numeric_limits_unsafe
{
  struct mu { };
 
  template<typename U>
    static U test(int);
 
  template<typename U>
    static mu test(...);
 
public:
    typedef std::is_same<decltype(test<T>(0)), mu> type;
};
 
template<typename T>
struct is_numeric_limits_safe
: std::integral_constant<bool, !is_numeric_limits_unsafe<T>::type::value>
{ };
 
int main()
{
    ::std::cout
        << is_numeric_limits_safe<int>::value << ::std::endl
        << is_numeric_limits_safe<int[]>::value << ::std::endl
        << is_numeric_limits_safe<int[2]>::value << ::std::endl
        << is_numeric_limits_safe<int()>::value << ::std::endl
        << is_numeric_limits_safe<my_abstract_class>::value << ::std::endl
        << is_numeric_limits_safe<my_incomplete_class>::value << ::std::endl
        ;
    return 0;
}

prog.cpp: In instantiation of ‘class is_numeric_limits_unsafe<my_abstract_class>’:
prog.cpp:23:8:   required from ‘struct is_numeric_limits_safe<my_abstract_class>’
prog.cpp:34:53:   required from here
prog.cpp:19:52: error: cannot allocate an object of abstract type ‘my_abstract_class’
prog.cpp:4:8: note:   because the following virtual functions are pure within ‘my_abstract_class’:
prog.cpp:4:40: note: 	virtual int my_abstract_class::x()
prog.cpp: In function ‘int main()’:
prog.cpp:34:12: error: ‘value’ is not a member of ‘is_numeric_limits_safe<my_abstract_class>’
prog.cpp: In instantiation of ‘class is_numeric_limits_unsafe<my_incomplete_class>’:
prog.cpp:23:8:   required from ‘struct is_numeric_limits_safe<my_incomplete_class>’
prog.cpp:35:55:   required from here
prog.cpp:19:52: error: invalid use of incomplete type ‘struct my_incomplete_class’
prog.cpp:5:8: error: forward declaration of ‘struct my_incomplete_class’
prog.cpp:35:12: error: ‘value’ is not a member of ‘is_numeric_limits_safe<my_incomplete_class>’

Standard output is empty