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// RUN: %clang_cc1 -std=c++1z -verify %s
// RUN: %clang_cc1 -std=c++2a -verify %s
template<typename ...T> constexpr auto sum(T ...t) { return (... + t); }
template<typename ...T> constexpr auto product(T ...t) { return (t * ...); }
template<typename ...T> constexpr auto all(T ...t) { return (true && ... && t); }
template<typename ...T> constexpr auto dumb(T ...t) { return (false && ... && t); }
static_assert(sum(1, 2, 3, 4, 5) == 15);
static_assert(product(1, 2, 3, 4, 5) == 120);
static_assert(!all(true, true, false, true, false));
static_assert(all(true, true, true, true, true));
static_assert(!dumb(true, true, true, true, true));
struct S {
int a, b, c, d, e;
};
template<typename ...T> constexpr auto increment_all(T &...t) {
(++t, ...);
}
constexpr bool check() {
S s = { 1, 2, 3, 4, 5 };
increment_all(s.a, s.b, s.c, s.d, s.e);
return s.a == 2 && s.b == 3 && s.c == 4 && s.d == 5 && s.e == 6;
}
static_assert(check());
template<int ...N> void empty() {
static_assert((N || ...) == false);
static_assert((N && ...) == true);
(N, ...);
}
template void empty<>();
// An empty fold-expression isn't a null pointer just because it's an integer
// with value 0. (This is no longer an issue since empty pack expansions don't
// produce integers any more.)
template<int ...N> void null_ptr() {
void *p = (N || ...); // expected-error {{rvalue of type 'bool'}}
void *q = (N , ...); // expected-error {{rvalue of type 'void'}}
}
template void null_ptr<>(); // expected-note {{in instantiation of}}
template<int ...N> void bad_empty() {
(N + ...); // expected-error {{empty expansion for operator '+' with no fallback}}
(N * ...); // expected-error {{empty expansion for operator '*' with no fallback}}
(N | ...); // expected-error {{empty expansion for operator '|' with no fallback}}
(N & ...); // expected-error {{empty expansion for operator '&' with no fallback}}
(N - ...); // expected-error {{empty expansion for operator '-' with no fallback}}
(N / ...); // expected-error {{empty expansion for operator '/' with no fallback}}
(N % ...); // expected-error {{empty expansion for operator '%' with no fallback}}
(N = ...); // expected-error {{empty expansion for operator '=' with no fallback}}
}
template void bad_empty<>(); // expected-note {{in instantiation of}}
template<int ...N> void empty_with_base() {
extern int k;
(k = ... = N); // expected-warning{{unused}}
void (k = ... = N); // expected-error {{expected ')'}} expected-note {{to match}}
void ((k = ... = N));
(void) (k = ... = N);
}
template void empty_with_base<>(); // expected-note {{in instantiation of}}
template void empty_with_base<1>();
struct A {
struct B {
struct C {
struct D {
int e;
} d;
} c;
} b;
} a;
template<typename T, typename ...Ts> constexpr decltype(auto) apply(T &t, Ts ...ts) {
return (t.*....*ts);
}
static_assert(&apply(a, &A::b, &A::B::c, &A::B::C::d, &A::B::C::D::e) == &a.b.c.d.e);
#if __cplusplus > 201703L
// The <=> operator is unique among binary operators in not being a
// fold-operator.
// FIXME: This diagnostic is not great.
template<typename ...T> constexpr auto spaceship1(T ...t) { return (t <=> ...); } // expected-error {{expected expression}}
template<typename ...T> constexpr auto spaceship2(T ...t) { return (... <=> t); } // expected-error {{expected expression}}
template<typename ...T> constexpr auto spaceship3(T ...t) { return (t <=> ... <=> 0); } // expected-error {{expected expression}}
#endif
// The GNU binary conditional operator ?: is not recognized as a fold-operator.
// FIXME: Why not? This seems like it would be useful.
template<typename ...T> constexpr auto binary_conditional1(T ...t) { return (t ?: ...); } // expected-error {{expected expression}}
template<typename ...T> constexpr auto binary_conditional2(T ...t) { return (... ?: t); } // expected-error {{expected expression}}
template<typename ...T> constexpr auto binary_conditional3(T ...t) { return (t ?: ... ?: 0); } // expected-error {{expected expression}}
namespace PR41845 {
template <int I> struct Constant {};
template <int... Is> struct Sum {
template <int... Js> using type = Constant<((Is + Js) + ... + 0)>; // expected-error {{pack expansion contains parameter pack 'Js' that has a different length (1 vs. 2) from outer parameter packs}}
};
Sum<1>::type<1, 2> x; // expected-note {{instantiation of}}
}
namespace PR30738 {
namespace N {
struct S {};
}
namespace T {
void operator+(N::S, N::S) {}
template<typename ...Ts> void f() { (Ts{} + ...); }
}
void g() { T::f<N::S, N::S>(); }
template<typename T, typename ...U> auto h(U ...v) {
T operator+(T, T); // expected-note {{candidate}}
return (v + ...); // expected-error {{invalid operands}}
}
int test_h1 = h<N::S>(1, 2, 3);
N::S test_h2 = h<N::S>(N::S(), N::S(), N::S());
int test_h3 = h<struct X>(1, 2, 3);
N::S test_h4 = h<struct X>(N::S(), N::S(), N::S()); // expected-note {{instantiation of}}
}
namespace GH67395 {
template <typename>
bool f();
template <typename... T>
void g(bool = (f<T>() || ...));
}
namespace comparison_warning {
struct S {
bool operator<(const S&) const;
bool operator<(int) const;
bool operator==(const S&) const;
};
template <typename...T>
void f(T... ts) {
(void)(ts == ...);
// expected-error@-1 2{{comparison in fold expression would evaluate to '(X == Y) == Z'}}
(void)(ts < ...);
// expected-error@-1 2{{comparison in fold expression would evaluate to '(X < Y) < Z'}}
(void)(... < ts);
// expected-error@-1 2{{comparison in fold expression would evaluate to '(X < Y) < Z'}}
}
void test() {
f(0, 1, 2); // expected-note{{in instantiation}}
f(0, 1); // expected-note{{in instantiation}}
f(S{}, S{});
f(0);
}
};
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