clang/test/CXX/temp/temp.constr/temp.constr.order/function-templates.cpp

// RUN: %clang_cc1 -std=c++2a -x c++ -verify %s

template<typename T> requires (sizeof(T) >= 4)
// expected-note@-1{{similar constraint expressions not considered equivalent}}
bool a() { return false; } // expected-note {{candidate function [with T = unsigned int]}}

template<typename T> requires (sizeof(T) >= 4 && sizeof(T) <= 10)
// expected-note@-1{{similar constraint expression here}}
bool a() { return true; } // expected-note {{candidate function [with T = unsigned int]}}

bool av = a<unsigned>(); // expected-error {{call to 'a' is ambiguous}}

template<typename T>
concept C1 = sizeof(T) >= 4;

template<typename T> requires C1<T>
constexpr bool b() { return false; }

template<typename T> requires (C1<T> && sizeof(T) <= 10)
constexpr bool b() { return true; }

static_assert(b<int>());
static_assert(!b<int[10]>());

template<typename T>
concept C2 = sizeof(T) > 1 && sizeof(T) <= 8;

template<typename T>
bool c() { return false; }

template<typename T> requires C1<T>
bool c() { return true; }

template<typename T> requires C1<T>
constexpr bool d() { return false; }

template<typename T>
constexpr bool d() { return true; }

static_assert(!d<int>());

template<typename T>
constexpr int e() { return 1; }

template<typename T> requires C1<T> && C2<T>
constexpr int e() { return 2; }

template<typename T> requires C1<T> || C2<T>
constexpr int e() { return 3; }

static_assert(e<unsigned>() == 2);
static_assert(e<char[10]>() == 3);
static_assert(e<char>() == 1);

template<class T, class U>
concept BiggerThan = sizeof(T) > sizeof(U);

template<class T>
concept BiggerThanInt = BiggerThan<T, int>;

template<class T, class U> requires BiggerThan<T, U>
void f() { }
// expected-note@-1 {{candidate function [with T = long long, U = int]}}

template<class T, class U> requires BiggerThanInt<T>
void f() { }
// expected-note@-1 {{candidate function [with T = long long, U = int]}}

static_assert(sizeof(f<long long, int>()));
// expected-error@-1 {{call to 'f' is ambiguous}} \
   expected-error@-1 {{invalid application of 'sizeof' to an incomplete type 'void'}}

template<typename T>
concept C3 = true;

template<typename T>
concept C4 = true && C3<T>;

template<typename T> requires C3<void>
int g() { }

template<typename T> requires C4<void>
int g() { }

static_assert(sizeof(g<int>()));

// Regression - used template parameter detection when only first out of
// multiple parameters are used
template <unsigned> struct X {};
template <class...> int h(X<0>);
template <unsigned b, class...> int h(X<b>);
static_assert(sizeof(h(X<0>{})));