1 // PR c++/62072
2 // { dg-do compile { target c++11 } }
3 
4 template<typename T> struct tuple_size {};
5 template<typename T> struct tuple_size<T const> : tuple_size<T> {};
6 
7 template<typename T, typename = void>
8 struct query {
9     static constexpr bool value = false;
10 };
11 template<typename T>
12 struct query<T, typename tuple_size<T>::type> {
13     static constexpr bool value = true;
14 };
15 
16 // fine
17 static_assert( !query<int>::value, "" );
18 static_assert( !query<int const>::value, "" );
19 
20 // error: invalid use of incomplete type 'struct tuple_size<void()>'
21 static_assert( !query<void()>::value, "" );
22