test/SemaTemplate/concepts.cpp

// RUN: %clang_cc1 -std=c++20 -verify %s

namespace PR47043 {
  template<typename T> concept True = true;
  template<typename ...T> concept AllTrue1 = True<T>; // expected-error {{expression contains unexpanded parameter pack 'T'}}
  template<typename ...T> concept AllTrue2 = (True<T> && ...);
  static_assert(AllTrue2<int, float, char>);
}

namespace PR47025 {
  template<typename ...T> concept AllAddable1 = requires(T ...t) { (void(t + 1), ...); };
  template<typename ...T> concept AllAddable2 = (requires(T ...t) { (t + 1); } && ...); // expected-error {{requirement contains unexpanded parameter pack 't'}}
  template<typename ...T> concept AllAddable3 = (requires(T t) { (t + 1); } && ...);
  template<typename ...T> concept AllAddable4 = requires(T t) { (t + 1); }; // expected-error {{expression contains unexpanded parameter pack 'T'}}
  template<typename ...T> concept AllAddable5 = requires(T t) { (void(t + 1), ...); }; // expected-error {{does not contain any unexpanded}}
  template<typename ...T> concept AllAddable6 = (requires { (T() + 1); } && ...);
  template<typename ...T> concept AllAddable7 = requires { (T() + 1); }; // expected-error {{expression contains unexpanded parameter pack 'T'}}

  static_assert(AllAddable1<int, float>);
  static_assert(AllAddable3<int, float>);
  static_assert(AllAddable6<int, float>);
  static_assert(!AllAddable1<int, void>);
  static_assert(!AllAddable3<int, void>);
  static_assert(!AllAddable6<int, void>);
}

namespace PR45699 {
  template<class> concept C = true; // expected-note 2{{here}}
  template<class ...Ts> void f1a() requires C<Ts>; // expected-error {{requires clause contains unexpanded parameter pack 'Ts'}}
  template<class ...Ts> requires C<Ts> void f1b(); // expected-error {{requires clause contains unexpanded parameter pack 'Ts'}}
  template<class ...Ts> void f2a() requires (C<Ts> && ...);
  template<class ...Ts> requires (C<Ts> && ...) void f2b();
  template<class ...Ts> void f3a() requires C<Ts...>; // expected-error {{pack expansion used as argument for non-pack parameter of concept}}
  template<class ...Ts> requires C<Ts...> void f3b(); // expected-error {{pack expansion used as argument for non-pack parameter of concept}}
  template<class ...Ts> void f4() {
    ([] () requires C<Ts> {} ()); // expected-error {{expression contains unexpanded parameter pack 'Ts'}}
    ([]<int = 0> requires C<Ts> () {} ()); // expected-error {{expression contains unexpanded parameter pack 'Ts'}}
  }
  template<class ...Ts> void f5() {
    ([] () requires C<Ts> {} (), ...);
    ([]<int = 0> requires C<Ts> () {} (), ...);
  }
  void g() {
    f1a();
    f1b(); // FIXME: Bad error recovery. expected-error {{undeclared identifier}}
    f2a();
    f2b();
    f3a();
    f3b(); // FIXME: Bad error recovery. expected-error {{undeclared identifier}}
    f4();
    f5();
  }
}

namespace P0857R0 {
  void f() {
    auto x = []<bool B> requires B {}; // expected-note {{constraints not satisfied}} expected-note {{false}}
    x.operator()<true>();
    x.operator()<false>(); // expected-error {{no matching member function}}
  }

  // FIXME: This is valid under P0857R0.
  template<typename T> concept C = true;
  template<template<typename T> requires C<T> typename U> struct X {}; // expected-error {{requires 'class'}} expected-error 0+{{}}
  template<typename T> requires C<T> struct Y {};
  X<Y> xy; // expected-error {{no template named 'X'}}
}

namespace PR50306 {
  template<typename T> concept NotInt = sizeof(T) != sizeof(int); // expected-note {{because}}
  template<typename T> void f() {
    [](NotInt auto) {}(T()); // expected-error {{no matching function}} expected-note {{constraints not satisfied}} expected-note {{because}}
  }
  template void f<char>(); // OK
  template void f<int>(); // expected-note {{in instantiation of}}
}

namespace PackInTypeConstraint {
  template<typename T, typename U> concept C = sizeof(T) == sizeof(int); // expected-note 3{{}}

  template<typename ...T, C<T> U> void h1(); // expected-error {{type constraint contains unexpanded parameter pack 'T'}}
  template<typename ...T, C<T> ...U> void h2();
  template<typename ...T> void h3(C<T> auto); // expected-error {{type constraint contains unexpanded parameter pack 'T'}}
  template<typename ...T> void h4(C<T> auto...);

  template<typename ...T> void f1() {
    []<C<T> U>(U u){}(T()); // expected-error {{unexpanded parameter pack 'T'}}
  }
  template<typename ...T> void f2() {
    ([]<C<T> U>(U u){}(T()), ...); // expected-error {{no match}} expected-note 2{{}}
  }
  template void f2<int, int, int>(); // OK
  template void f2<int, char, double>(); // expected-note {{in instantiation of}}
  void f3() {
    ([]<typename ...T, C<T> U>(U u){}(0), // expected-error {{type constraint contains unexpanded parameter pack 'T'}}
     ...); // expected-error {{does not contain any unexpanded}}
  }

  template<typename ...T> void g1() {
    [](C<T> auto){}(T()); // expected-error {{expression contains unexpanded parameter pack 'T'}}
  }
  template<typename ...T> void g2() {
    ([](C<T> auto){}(T()), ...); // expected-error {{no matching function}} expected-note {{constraints not satisfied}} expected-note {{because}}
  }
  template void g2<int, int, int>(); // OK
  template void g2<int, char, double>(); // expected-note {{in instantiation of}}
  void g3() {
    ([]<typename ...T>(C<T> auto){}(1), // expected-error {{type constraint contains unexpanded parameter pack 'T'}}
     ...); // expected-error {{does not contain any unexpanded}}
  }

  template<typename ...T> void g4() {
    []() -> C<T> auto{ return T(); }(); // expected-error {{expression contains unexpanded parameter pack 'T'}}
  }
  template<typename ...T> void g5() {
    ([]() -> C<T> auto{ // expected-error-re {{deduced type {{.*}} does not satisfy}}
     return T();
     }(), ...);
  }
  template void g5<int, int, int>(); // OK
  template void g5<int, char, double>(); // expected-note {{in instantiation of}}
  void g6() {
    ([]<typename ...T>() -> C<T> auto{ // expected-error {{declaration type contains unexpanded parameter pack 'T'}}
     return T(); // expected-error {{expression contains unexpanded parameter pack 'T'}}
     }(),
     ...); // expected-error {{does not contain any unexpanded}}
  }
}

namespace BuiltinIsConstantEvaluated {
  // Check that we do all satisfaction and diagnostic checks in a constant context.
  template<typename T> concept C = __builtin_is_constant_evaluated(); // expected-warning {{always}}
  static_assert(C<int>);

  template<typename T> concept D = __builtin_is_constant_evaluated() == true; // expected-warning {{always}}
  static_assert(D<int>);

  template<typename T> concept E = __builtin_is_constant_evaluated() == true && // expected-warning {{always}}
                                   false; // expected-note {{'false' evaluated to false}}
  static_assert(E<int>); // expected-error {{failed}} expected-note {{because 'int' does not satisfy 'E'}}

  template<typename T> concept F = __builtin_is_constant_evaluated() == false; // expected-warning {{always}}
  // expected-note@-1 {{'__builtin_is_constant_evaluated() == false' (1 == 0)}}
  static_assert(F<int>); // expected-error {{failed}} expected-note {{because 'int' does not satisfy 'F'}}

  template<typename T> concept G = __builtin_is_constant_evaluated() && // expected-warning {{always}}
                                   false; // expected-note {{'false' evaluated to false}}
  static_assert(G<int>); // expected-error {{failed}} expected-note {{because 'int' does not satisfy 'G'}}
}

namespace NoConstantFolding {
  // Ensure we use strict constant evaluation rules when checking satisfaction.
  int n;
  template <class T> concept C = &n + 3 - 3 == &n; // expected-error {{non-constant expression}} expected-note {{cannot refer to element 3 of non-array object}}
  static_assert(C<void>); // expected-note {{while checking}}
}

namespace PR50337 {
  template <typename T> concept foo = true;
  template <typename T> concept foo2 = foo<T> && true;
  void f(foo auto, auto);
  void f(foo2 auto, auto);
  void g() { f(1, 2); }
}

namespace PR50561 {
  template<typename> concept C = false;
  template<typename T, typename U> void f(T, U);
  template<C T, typename U> void f(T, U) = delete;
  void g() { f(0, 0); }
}