1 // RUN: %clang_cc1 -verify -std=c++1z %s
2
3 namespace Explicit {
4 // Each notional constructor is explicit if the function or function template
5 // was generated from a constructor or deduction-guide that was declared explicit.
6 template<typename T> struct A {
7 A(T);
8 A(T*);
9 A(...);
10 };
11 template<typename T> A(T) -> A<T>;
12 template<typename T> explicit A(T*) -> A<T**>; // expected-note {{explicit}}
13
14 int *p;
15 A a(p);
16 A b = p;
17 A c{p};
18 A d = {p}; // expected-error {{selected an explicit deduction guide}}
19
20 using X = A<int**>;
21 using Y = A<int>; // uses the implicit guide, being more specialized than the eligible user-defined deduction guides.
22
23 using X = decltype(a);
24 using Y = decltype(b);
25 using X = decltype(c);
26 }
27
28
29 namespace std {
30 template<typename T> struct initializer_list {
31 const T *ptr;
32 __SIZE_TYPE__ size;
33 initializer_list();
34 };
35 }
36
37 namespace p0702r1 {
38 template<typename T> struct X { // expected-note {{candidate}}
39 X(std::initializer_list<T>); // expected-note {{candidate}}
40 };
41
42 X xi = {0};
43 X xxi = {xi};
44 extern X<int> xi;
45 // Prior to P0702R1, this is X<X<int>>.
46 extern X<int> xxi;
47
48 struct Y : X<int> {};
49 Y y {{0}};
50 X xy {y};
51 extern X<int> xy;
52
53 struct Z : X<int>, X<float> {};
54 Z z = {{0}, {0.0f}};
55 // This is not X<Z> even though that would work. Instead, it's ambiguous
56 // between X<int> and X<float>.
57 X xz = {z}; // expected-error {{no viable constructor or deduction guide}}
58 }
59 namespace pr34970 {
60 //https://bugs.llvm.org/show_bug.cgi?id=34970
61
62 template <typename X, typename Y> struct IsSame {
63 static constexpr bool value = false;
64 };
65
66 template <typename Z> struct IsSame<Z, Z> {
67 static constexpr bool value = true;
68 };
69
70 template <typename T> struct Optional {
Optionalpr34970::Optional71 template <typename U> Optional(U&&) { }
72 };
73
74 template <typename A> Optional(A) -> Optional<A>;
75
main()76 int main() {
77 Optional opt(1729);
78 Optional dupe(opt);
79
80 static_assert(IsSame<decltype(opt), Optional<int>>::value);
81 static_assert(IsSame<decltype(dupe), Optional<int>>::value);
82 static_assert(!IsSame<decltype(dupe), Optional<Optional<int>>>::value);
83 return 0;
84 }
85
86
87 }