libcxx/test/std/containers/views/mdspan/default_accessor/ctor.conversion.pass.cpp

   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, c++20
  10
  11 // <mdspan>
  12 //
  13 // Test converting constructor:
  14 //
  15 // template<class OtherElementType>
  16 //   constexpr default_accessor(default_accessor<OtherElementType>) noexcept {}
  17 //
  18 // Constraints: is_convertible_v<OtherElementType(*)[], element_type(*)[]> is true.
  19
  20 #include <mdspan>
  21 #include <cassert>
  22 #include <cstdint>
  23 #include <type_traits>
  24
  25 #include "test_macros.h"
  26
  27 #include "../MinimalElementType.h"
  28
  29 struct Base {};
  30 struct Derived: public Base {};
  31
  32 template <class FromT, class ToT>
  33 constexpr void test_conversion() {
  34   std::default_accessor<FromT> acc_from;
  35   ASSERT_NOEXCEPT(std::default_accessor<ToT>(acc_from));
  36   [[maybe_unused]] std::default_accessor<ToT> acc_to(acc_from);
  37 }
  38
  39 constexpr bool test() {
  40   // default accessor conversion largely behaves like pointer conversion
  41   test_conversion<int, int>();
  42   test_conversion<int, const int>();
  43   test_conversion<const int, const int>();
  44   test_conversion<MinimalElementType, MinimalElementType>();
  45   test_conversion<MinimalElementType, const MinimalElementType>();
  46   test_conversion<const MinimalElementType, const MinimalElementType>();
  47
  48   // char is convertible to int, but accessors are not
  49   static_assert(!std::is_constructible_v<std::default_accessor<int>, std::default_accessor<char>>);
  50   // don't allow conversion from const elements to non-const
  51   static_assert(!std::is_constructible_v<std::default_accessor<int>, std::default_accessor<const int>>);
  52   // MinimalElementType is constructible from int, but accessors should not be convertible
  53   static_assert(!std::is_constructible_v<std::default_accessor<MinimalElementType>, std::default_accessor<int>>);
  54   // don't allow conversion from const elements to non-const
  55   static_assert(!std::is_constructible_v<std::default_accessor<MinimalElementType>, std::default_accessor<const MinimalElementType>>);
  56   // don't allow conversion from Base to Derived
  57   static_assert(!std::is_constructible_v<std::default_accessor<Derived>, std::default_accessor<Base>>);
  58   // don't allow conversion from Derived to Base
  59   static_assert(!std::is_constructible_v<std::default_accessor<Base>, std::default_accessor<Derived>>);
  60
  61   return true;
  62 }
  63
  64 int main(int, char**) {
  65   test();
  66   static_assert(test());
  67   return 0;
  68 }