| 1 | // RUN: %clang_cc1 -std=c++11 -fsyntax-only -verify %s |
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| 2 | // RUN: %clang_cc1 -std=c++1z -fsyntax-only -verify %s |
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| 3 | |
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| 4 | // A forwarding reference is an rvalue reference to a cv-unqualified template |
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| 5 | // parameter that does not represent a template parameter of a class template. |
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| 6 | #if __cplusplus > 201402L |
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| 7 | namespace ClassTemplateParamNotForwardingRef { |
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| 8 | // This is not a forwarding reference. |
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| 9 | template<typename T> struct A { // expected-note {{candidate}} |
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| 10 | A(T&&); // expected-note {{no known conversion from 'int' to 'int &&'}} |
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| 11 | }; |
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| 12 | int n; |
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| 13 | A a = n; // expected-error {{no viable constructor or deduction guide}} |
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| 14 | |
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| 15 | A b = 0; |
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| 16 | A<int> *pb = &b; |
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| 17 | |
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| 18 | // This is a forwarding reference. |
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| 19 | template<typename T> A(T&&) -> A<T>; |
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| 20 | A c = n; |
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| 21 | A<int&> *pc = &c; |
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| 22 | |
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| 23 | A d = 0; |
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| 24 | A<int> *pd = &d; |
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| 25 | |
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| 26 | template<typename T = void> struct B { |
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| 27 | // This is a forwarding reference. |
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| 28 | template<typename U> B(U &&); |
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| 29 | }; |
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| 30 | B e = n; |
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| 31 | B<void> *pe = &e; |
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| 32 | } |
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| 33 | #endif |
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| 34 | |
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| 35 | // If P is a forwarding reference and the argument is an lvalue, the type |
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| 36 | // "lvalue reference to A" is used in place of A for type deduction. |
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| 37 | template<typename T> struct X { }; |
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| 38 | |
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| 39 | template<typename T> X<T> f0(T&&); |
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| 40 | |
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| 41 | struct Y { }; |
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| 42 | |
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| 43 | template<typename T> T prvalue(); |
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| 44 | template<typename T> T&& xvalue(); |
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| 45 | template<typename T> T& lvalue(); |
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| 46 | |
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| 47 | void test_f0() { |
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| 48 | X<int> xi0 = f0(prvalue<int>()); |
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| 49 | X<int> xi1 = f0(xvalue<int>()); |
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| 50 | X<int&> xi2 = f0(lvalue<int>()); |
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| 51 | X<Y> xy0 = f0(prvalue<Y>()); |
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| 52 | X<Y> xy1 = f0(xvalue<Y>()); |
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| 53 | X<Y&> xy2 = f0(lvalue<Y>()); |
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| 54 | } |
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| 55 | |
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| 56 | template<typename T> X<T> f1(const T&&); // expected-note{{candidate function [with T = int] not viable: no known conversion from 'int' to 'const int &&' for 1st argument}} \ |
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| 57 | // expected-note{{candidate function [with T = Y] not viable: no known conversion from 'Y' to 'const Y &&' for 1st argument}} |
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| 58 | |
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| 59 | void test_f1() { |
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| 60 | X<int> xi0 = f1(prvalue<int>()); |
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| 61 | X<int> xi1 = f1(xvalue<int>()); |
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| 62 | f1(lvalue<int>()); // expected-error{{no matching function for call to 'f1'}} |
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| 63 | X<Y> xy0 = f1(prvalue<Y>()); |
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| 64 | X<Y> xy1 = f1(xvalue<Y>()); |
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| 65 | f1(lvalue<Y>()); // expected-error{{no matching function for call to 'f1'}} |
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| 66 | } |
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| 67 | |
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| 68 | namespace std_example { |
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| 69 | template <class T> int f(T&&); |
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| 70 | template <class T> int g(const T&&); // expected-note{{candidate function [with T = int] not viable: no known conversion from 'int' to 'const int &&' for 1st argument}} |
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| 71 | |
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| 72 | int i; |
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| 73 | int n1 = f(i); |
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| 74 | int n2 = f(0); |
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| 75 | int n3 = g(i); // expected-error{{no matching function for call to 'g'}} |
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| 76 | |
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| 77 | #if __cplusplus > 201402L |
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| 78 | template<class T> struct A { // expected-note {{candidate}} |
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| 79 | template<class U> |
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| 80 | A(T &&, U &&, int *); // expected-note {{[with T = int, U = int] not viable: no known conversion from 'int' to 'int &&'}} |
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| 81 | A(T &&, int *); // expected-note {{requires 2}} |
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| 82 | }; |
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| 83 | template<class T> A(T &&, int *) -> A<T>; // expected-note {{requires 2}} |
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| 84 | |
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| 85 | int *ip; |
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| 86 | A a{i, 0, ip}; // expected-error {{no viable constructor or deduction guide}} |
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| 87 | A a0{0, 0, ip}; |
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| 88 | A a2{i, ip}; |
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| 89 | |
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| 90 | A<int> &a0r = a0; |
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| 91 | A<int&> &a2r = a2; |
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| 92 | #endif |
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| 93 | } |
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| 94 | |
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