p3.cpp source code [clang_source_code/test/CXX/over/over.match/over.match.funcs/over.match.class.deduct/p3.cpp]

1	// RUN: %clang_cc1 -std=c++1z -verify %s
2
3	namespace std_example {
4	template <class T> struct A {
5	explicit A(const T &, ...) noexcept; // expected-note {{explicit}} expected-note 2{{candidate}}
6	A(T &&, ...); // expected-note 2{{candidate}}
7	};
8
9	int i;
10	A a1 = {i, i}; // expected-error {{class template argument deduction for 'A' selected an explicit constructor for copy-list-initialization}}
11	A a2{i, i};
12	A a3{0, i};
13	A a4 = {0, i};
14
15	template <class T> A(const T &, const T &) -> A<T &>; // expected-note 2{{candidate}}
16	template <class T> explicit A(T &&, T &&) -> A<T>; // expected-note {{explicit deduction guide declared here}}
17
18	// FIXME: The standard gives an incorrect explanation for why a5, a7, and a8 are ill-formed.
19	A a5 = {0, 1}; // expected-error {{class template argument deduction for 'A' selected an explicit deduction guide}}
20	A a6{0, 1};
21	A a7 = {0, i}; // expected-error {{ambiguous deduction}}
22	A a8{0, i}; // expected-error {{ambiguous deduction}}
23
24	template <class T> struct B {
25	template <class U> using TA = T;
26	template <class U> B(U, TA<U>);
27	};
28	B b{(int )0, (char )0};
29	}
30
31	namespace check {
32	using namespace std_example;
33	template<typename T, typename U> constexpr bool same = false;
34	template<typename T> constexpr bool same<T, T> = true;
35
36	static_assert(same<decltype(a2), A<int>>);
37	static_assert(same<decltype(a3), A<int>>);
38	static_assert(same<decltype(a4), A<int>>);
39	static_assert(same<decltype(a6), A<int>>);
40	static_assert(same<decltype(b), B<char*>>);
41	}
42

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