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1 | // Copyright (c) 2018 Andrey Semashev |
2 | // | |
3 | // Use, modification, and distribution is subject to the Boost Software | |
4 | // License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at | |
5 | // http://www.boost.org/LICENSE_1_0.txt) | |
6 | ||
7 | // The test verifies that Boost.Optional copy constructors do not attempt to invoke | |
8 | // the element type initializing constructors from templated arguments | |
9 | ||
10 | #include <boost/optional/optional.hpp> | |
11 | #include <boost/core/enable_if.hpp> | |
12 | ||
13 | struct no_type | |
14 | { | |
15 | char data; | |
16 | }; | |
17 | ||
18 | struct yes_type | |
19 | { | |
20 | char data[2]; | |
21 | }; | |
22 | ||
23 | template< unsigned int Size > | |
24 | struct size_tag {}; | |
25 | ||
26 | template< typename T, typename U > | |
27 | struct is_constructible | |
28 | { | |
f67539c2 TL |
29 | static U& get(); |
30 | ||
31 | template< typename T1 > | |
32 | static yes_type check_helper(size_tag< sizeof(static_cast< T1 >(get())) >*); | |
33 | template< typename T1 > | |
92f5a8d4 TL |
34 | static no_type check_helper(...); |
35 | ||
f67539c2 | 36 | static const bool value = sizeof(check_helper< T >(0)) == sizeof(yes_type); |
92f5a8d4 TL |
37 | }; |
38 | ||
39 | template< typename T > | |
40 | class wrapper | |
41 | { | |
42 | public: | |
43 | wrapper() {} | |
44 | wrapper(wrapper const&) {} | |
45 | template< typename U > | |
46 | wrapper(U const&, typename boost::enable_if_c< is_constructible< T, U >::value, int >::type = 0) {} | |
47 | }; | |
48 | ||
49 | inline boost::optional< wrapper< int > > foo() | |
50 | { | |
51 | return boost::optional< wrapper< int > >(); | |
52 | } | |
53 | ||
54 | int main() | |
55 | { | |
56 | // Invokes boost::optional copy constructor. Should not invoke wrapper constructor from U. | |
57 | boost::optional< wrapper< int > > res = foo(); | |
58 | return 0; | |
59 | } |