1 // RUN: %clang_cc1 -std=c++1z -verify %s
2 // RUN: %clang_cc1 -std=c++2a -verify %s
3
sum(T...t)4 template<typename ...T> constexpr auto sum(T ...t) { return (... + t); }
product(T...t)5 template<typename ...T> constexpr auto product(T ...t) { return (t * ...); }
all(T...t)6 template<typename ...T> constexpr auto all(T ...t) { return (true && ... && t); }
dumb(T...t)7 template<typename ...T> constexpr auto dumb(T ...t) { return (false && ... && t); }
8
9 static_assert(sum(1, 2, 3, 4, 5) == 15);
10 static_assert(product(1, 2, 3, 4, 5) == 120);
11 static_assert(!all(true, true, false, true, false));
12 static_assert(all(true, true, true, true, true));
13 static_assert(!dumb(true, true, true, true, true));
14
15 struct S {
16 int a, b, c, d, e;
17 };
increment_all(T &...t)18 template<typename ...T> constexpr auto increment_all(T &...t) {
19 (++t, ...);
20 }
check()21 constexpr bool check() {
22 S s = { 1, 2, 3, 4, 5 };
23 increment_all(s.a, s.b, s.c, s.d, s.e);
24 return s.a == 2 && s.b == 3 && s.c == 4 && s.d == 5 && s.e == 6;
25 }
26 static_assert(check());
27
empty()28 template<int ...N> void empty() {
29 static_assert((N || ...) == false);
30 static_assert((N && ...) == true);
31 (N, ...);
32 }
33 template void empty<>();
34
35 // An empty fold-expression isn't a null pointer just because it's an integer
36 // with value 0. (This is no longer an issue since empty pack expansions don't
37 // produce integers any more.)
null_ptr()38 template<int ...N> void null_ptr() {
39 void *p = (N || ...); // expected-error {{rvalue of type 'bool'}}
40 void *q = (N , ...); // expected-error {{rvalue of type 'void'}}
41 }
42 template void null_ptr<>(); // expected-note {{in instantiation of}}
43
bad_empty()44 template<int ...N> void bad_empty() {
45 (N + ...); // expected-error {{empty expansion for operator '+' with no fallback}}
46 (N * ...); // expected-error {{empty expansion for operator '*' with no fallback}}
47 (N | ...); // expected-error {{empty expansion for operator '|' with no fallback}}
48 (N & ...); // expected-error {{empty expansion for operator '&' with no fallback}}
49 (N - ...); // expected-error {{empty expansion for operator '-' with no fallback}}
50 (N / ...); // expected-error {{empty expansion for operator '/' with no fallback}}
51 (N % ...); // expected-error {{empty expansion for operator '%' with no fallback}}
52 (N = ...); // expected-error {{empty expansion for operator '=' with no fallback}}
53 }
54 template void bad_empty<>(); // expected-note {{in instantiation of}}
55
empty_with_base()56 template<int ...N> void empty_with_base() {
57 extern int k;
58 (k = ... = N); // expected-warning{{unused}}
59
60 void (k = ... = N); // expected-error {{expected ')'}} expected-note {{to match}}
61 void ((k = ... = N));
62 (void) (k = ... = N);
63 }
64 template void empty_with_base<>(); // expected-note {{in instantiation of}}
65 template void empty_with_base<1>();
66
67 struct A {
68 struct B {
69 struct C {
70 struct D {
71 int e;
72 } d;
73 } c;
74 } b;
75 } a;
apply(T & t,Ts...ts)76 template<typename T, typename ...Ts> constexpr decltype(auto) apply(T &t, Ts ...ts) {
77 return (t.*....*ts);
78 }
79 static_assert(&apply(a, &A::b, &A::B::c, &A::B::C::d, &A::B::C::D::e) == &a.b.c.d.e);
80
81 #if __cplusplus > 201703L
82 // The <=> operator is unique among binary operators in not being a
83 // fold-operator.
84 // FIXME: This diagnostic is not great.
spaceship1(T...t)85 template<typename ...T> constexpr auto spaceship1(T ...t) { return (t <=> ...); } // expected-error {{expected expression}}
spaceship2(T...t)86 template<typename ...T> constexpr auto spaceship2(T ...t) { return (... <=> t); } // expected-error {{expected expression}}
spaceship3(T...t)87 template<typename ...T> constexpr auto spaceship3(T ...t) { return (t <=> ... <=> 0); } // expected-error {{expected expression}}
88 #endif
89
90 // The GNU binary conditional operator ?: is not recognized as a fold-operator.
91 // FIXME: Why not? This seems like it would be useful.
binary_conditional1(T...t)92 template<typename ...T> constexpr auto binary_conditional1(T ...t) { return (t ?: ...); } // expected-error {{expected expression}}
binary_conditional2(T...t)93 template<typename ...T> constexpr auto binary_conditional2(T ...t) { return (... ?: t); } // expected-error {{expected expression}}
binary_conditional3(T...t)94 template<typename ...T> constexpr auto binary_conditional3(T ...t) { return (t ?: ... ?: 0); } // expected-error {{expected expression}}
95
96 namespace PR41845 {
97 template <int I> struct Constant {};
98
99 template <int... Is> struct Sum {
100 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}}
101 };
102
103 Sum<1>::type<1, 2> x; // expected-note {{instantiation of}}
104 }
105