gcc/testsuite/g++.dg/cpp2a/concepts-pr66962.C

// PR c++/66962
// { dg-do compile { target c++20 } }

template <typename> struct remove_cv;
template <typename> struct is_reference;
template <typename> void declval();
template <typename> struct is_constructible;
template <typename> struct is_nothrow_constructible;
template <typename _Tp> using remove_cv_t = typename remove_cv<_Tp>::type;
template <typename> struct Trans_NS_extension_apply_list;
template <typename T> using _t = typename T::type;
template <class> void ImplicitlyConvertibleTo();
template <class> void Assignable();
template <class T, class... Args> int ConstructibleObject = requires { T{}; };

template <class T, class... Args>
concept BindableReference = 
  is_reference<T>::value && is_constructible<T>::value;

template <class T, class... Args> 
concept Constructible = 
  ConstructibleObject<T> || BindableReference<T, Args...>;

template <class T> 
concept DefaultConstructible = 
  Constructible<T> && requires { new T[0]; };

template <class T> 
concept MoveConstructible =
  Constructible<T> && ImplicitlyConvertibleTo<T>;

template <class T>
concept Movable =
  MoveConstructible<T> && Assignable<T &&>;

template <class, class>
int Swappable_ = requires { 0; };

template <class T, class U> 
int Swappable();

template <class T> 
concept Dereferencable = requires{{0};};

template <Dereferencable R> 
using RvalueReferenceType = decltype(0);

template <class T> 
int IsValueType;

template <class>
struct value_type;

template <class T>
  requires IsValueType<_t<value_type<remove_cv_t<T>>>>
using ValueType = _t<value_type<remove_cv_t<T>>>;

template <class I> 
concept Readable =
  Movable<I> && DefaultConstructible<I> && Dereferencable<const I> && requires{{0};};

template <class Out, class T> 
concept MoveWritable =
  Movable<Out> && DefaultConstructible<Out> && Dereferencable<Out>;

template <class In, class Out> 
concept IndirectlyMovable =
  Readable<In> && 
  Movable<ValueType<In>> && 
  Constructible<ValueType<In>> &&
  MoveWritable<Out, RvalueReferenceType<In>> &&
  MoveWritable<Out, ValueType<In>>;

template<typename In, typename Out>
  requires IndirectlyMovable<In, Out>
int is_nothrow_indirectly_movable_v = is_nothrow_constructible<ValueType<In>>::value;

template <Readable R1, Readable R2>
  requires IndirectlyMovable<R1, R2> && IndirectlyMovable<R2, R1>
void iter_swap2();