1 //===----------------------------------------------------------------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 
9 // UNSUPPORTED: c++03, c++11, c++14, c++17
10 // UNSUPPORTED: libcpp-no-concepts
11 // UNSUPPORTED: libcpp-has-no-incomplete-ranges
12 
13 // template<class R>
14 //   drop_view(R&&, range_difference_t<R>) -> drop_view<views::all_t<R>>;
15 
16 #include <cassert>
17 #include <concepts>
18 #include <ranges>
19 #include <utility>
20 
21 struct View : std::ranges::view_base {
22   int *begin() const;
23   int *end() const;
24 };
25 
26 struct Range {
27   int *begin() const;
28   int *end() const;
29 };
30 
31 struct BorrowedRange {
32   int *begin() const;
33   int *end() const;
34 };
35 template<>
36 inline constexpr bool std::ranges::enable_borrowed_range<BorrowedRange> = true;
37 
38 void testCTAD() {
39     View v;
40     Range r;
41     BorrowedRange br;
42 
43     static_assert(std::same_as<
44         decltype(std::ranges::drop_view(v, 0)),
45         std::ranges::drop_view<View>
46     >);
47     static_assert(std::same_as<
48         decltype(std::ranges::drop_view(std::move(v), 0)),
49         std::ranges::drop_view<View>
50     >);
51     static_assert(std::same_as<
52         decltype(std::ranges::drop_view(r, 0)),
53         std::ranges::drop_view<std::ranges::ref_view<Range>>
54     >);
55     static_assert(std::same_as<
56         decltype(std::ranges::drop_view(std::move(r), 0)),
57         std::ranges::drop_view<std::ranges::owning_view<Range>>
58     >);
59     static_assert(std::same_as<
60         decltype(std::ranges::drop_view(br, 0)),
61         std::ranges::drop_view<std::ranges::ref_view<BorrowedRange>>
62     >);
63     static_assert(std::same_as<
64         decltype(std::ranges::drop_view(std::move(br), 0)),
65         std::ranges::drop_view<std::ranges::owning_view<BorrowedRange>>
66     >);
67 }
68