124 lines · cpp
1// RUN: %clang_cc1 -verify -std=c++1z %s2 3namespace Explicit {4 // Each notional constructor is explicit if the function or function template5 // 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 29namespace std {30 template<typename T> struct initializer_list {31 const T *ptr;32 __SIZE_TYPE__ size;33 initializer_list();34 };35}36 37namespace p0702r1 {38 template<typename T> struct X { // expected-note {{candidate}} expected-note {{implicit deduction guide}}39 X(std::initializer_list<T>); // expected-note {{candidate template ignored: could not match 'std::initializer_list<T>' against 'Z'}} \40 // expected-note {{implicit deduction guide declared as 'template <typename T> X(std::initializer_list<T>) -> p0702r1::X<T>'}}41 };42 43 X xi = {0};44 X xxi = {xi};45 extern X<int> xi;46 // Prior to P0702R1, this is X<X<int>>.47 extern X<int> xxi;48 49 struct Y : X<int> {};50 Y y {{0}};51 X xy {y};52 extern X<int> xy;53 54 struct Z : X<int>, X<float> {};55 Z z = {{0}, {0.0f}};56 // This is not X<Z> even though that would work. Instead, it's ambiguous57 // between X<int> and X<float>.58 X xz = {z}; // expected-error {{no viable constructor or deduction guide}}59}60namespace pr34970 {61//https://bugs.llvm.org/show_bug.cgi?id=3497062 63template <typename X, typename Y> struct IsSame {64 static constexpr bool value = false;65};66 67template <typename Z> struct IsSame<Z, Z> {68 static constexpr bool value = true;69};70 71template <typename T> struct Optional {72 template <typename U> Optional(U&&) { }73};74 75template <typename A> Optional(A) -> Optional<A>;76 77int main() {78 Optional opt(1729);79 Optional dupe(opt);80 81 static_assert(IsSame<decltype(opt), Optional<int>>::value);82 static_assert(IsSame<decltype(dupe), Optional<int>>::value);83 static_assert(!IsSame<decltype(dupe), Optional<Optional<int>>>::value);84 return 0;85}86 87 88}89 90namespace deduceTemplatedConstructor {91template <typename X, typename Y> struct IsSame {92 static constexpr bool value = false;93};94 95template <typename Z> struct IsSame<Z, Z> {96 static constexpr bool value = true;97};98template <class T> struct A {99 using value_type = T;100 A(value_type);101 A(const A&);102 A(T, T, int);103 template<class U>104 A(int, T, U);105};106 107A x(1, 2, 3); // no-error108static_assert(IsSame<decltype(x),A<int>>::value);109 110template <class T>111A(T) -> A<T>;112 113A a(42);114static_assert(IsSame<decltype(a),A<int>>::value);115A b = a;116static_assert(IsSame<decltype(b),A<int>>::value);117 118template <class T>119A(A<T>) -> A<A<T>>;120 121A b2 = a;122static_assert(IsSame<decltype(b2),A<A<int>>>::value);123}124