96 lines · cpp
1// RUN: %clang_cc1 -std=c++11 -fsyntax-only -verify %s2// RUN: %clang_cc1 -std=c++1z -fsyntax-only -verify %s3 4// A forwarding reference is an rvalue reference to a cv-unqualified template5// parameter that does not represent a template parameter of a class template.6#if __cplusplus > 201402L7namespace ClassTemplateParamNotForwardingRef {8 // This is not a forwarding reference.9 template<typename T> struct A { // expected-note {{candidate}} expected-note {{implicit deduction guide}}10 A(T&&); // expected-note {{expects an rvalue}} expected-note {{implicit deduction guide}}11 };12 int n;13 A a = n; // expected-error {{no viable constructor or deduction guide}}14 15 A b = 0;16 A<int> *pb = &b;17 18 // This is a forwarding reference.19 template<typename T> A(T&&) -> A<T>;20 A c = n;21 A<int&> *pc = &c;22 23 A d = 0;24 A<int> *pd = &d;25 26 template<typename T = void> struct B {27 // This is a forwarding reference.28 template<typename U> B(U &&);29 };30 B e = n;31 B<void> *pe = &e;32}33#endif34 35// If P is a forwarding reference and the argument is an lvalue, the type36// "lvalue reference to A" is used in place of A for type deduction.37template<typename T> struct X { };38 39template<typename T> X<T> f0(T&&);40 41struct Y { };42 43template<typename T> T prvalue();44template<typename T> T&& xvalue();45template<typename T> T& lvalue();46 47void test_f0() {48 X<int> xi0 = f0(prvalue<int>());49 X<int> xi1 = f0(xvalue<int>());50 X<int&> xi2 = f0(lvalue<int>());51 X<Y> xy0 = f0(prvalue<Y>());52 X<Y> xy1 = f0(xvalue<Y>());53 X<Y&> xy2 = f0(lvalue<Y>());54}55 56template<typename T> X<T> f1(const T&&); // expected-note{{candidate function [with T = int] not viable: expects an rvalue for 1st argument}} \57// expected-note{{candidate function [with T = Y] not viable: expects an rvalue for 1st argument}}58 59void test_f1() {60 X<int> xi0 = f1(prvalue<int>());61 X<int> xi1 = f1(xvalue<int>());62 f1(lvalue<int>()); // expected-error{{no matching function for call to 'f1'}}63 X<Y> xy0 = f1(prvalue<Y>());64 X<Y> xy1 = f1(xvalue<Y>());65 f1(lvalue<Y>()); // expected-error{{no matching function for call to 'f1'}}66}67 68namespace std_example {69 template <class T> int f(T&&);70 template <class T> int g(const T&&); // expected-note{{candidate function [with T = int] not viable: expects an rvalue for 1st argument}}71 72 int i;73 int n1 = f(i);74 int n2 = f(0);75 int n3 = g(i); // expected-error{{no matching function for call to 'g'}}76 77#if __cplusplus > 201402L78 template<class T> struct A { // expected-note {{candidate}} expected-note {{implicit deduction guide}}79 template<class U>80 A(T &&, U &&, int *); // expected-note {{[with T = int, U = int] not viable: expects an rvalue}} \81 // expected-note {{implicit deduction guide declared as 'template <class T, class U> A(T &&, U &&, int *) -> std_example::A<T>'}}82 A(T &&, int *); // expected-note {{requires 2}} \83 // expected-note {{implicit deduction guide declared as 'template <class T> A(T &&, int *) -> std_example::A<T>'}}84 };85 template<class T> A(T &&, int *) -> A<T>; // expected-note {{requires 2}}86 87 int *ip;88 A a{i, 0, ip}; // expected-error {{no viable constructor or deduction guide}}89 A a0{0, 0, ip};90 A a2{i, ip};91 92 A<int> &a0r = a0;93 A<int&> &a2r = a2;94#endif95}96