array.pass.cpp

//===----------------------------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//

// REQUIRES: std-at-least-c++20

// <span>

// template<size_t N> constexpr span(type_identity_t<element_type> (&arr)[N]) noexcept;
//
// Constraints: Let U be remove_pointer_t<decltype(std::data(arr))>.
//   - extent == dynamic_extent || N == extent is true, and
//   - is_convertible_v<U(*)[], element_type(*)[]> is true.

#include <cassert>
#include <span>
#include <string>
#include <type_traits>

#include "test_macros.h"

void checkCV() {
  int arr[]                  = {1, 2, 3};
  const int carr[]           = {4, 5, 6};
  volatile int varr[]        = {7, 8, 9};
  const volatile int cvarr[] = {1, 3, 5};

  // Types the same (dynamic sized)
  {
    std::span<int> s1{arr};                  // a span<int> pointing at int.
    std::span<const int> s2{carr};           // a span<const int> pointing at const int.
    std::span<volatile int> s3{varr};        // a span<volatile int> pointing at volatile int.
    std::span<const volatile int> s4{cvarr}; // a span<const volatile int> pointing at const volatile int.
    assert(s1.size() + s2.size() + s3.size() + s4.size() == 12);
  }

  // Types the same (static sized)
  {
    std::span<int, 3> s1{arr};                  // a span<int> pointing at int.
    std::span<const int, 3> s2{carr};           // a span<const int> pointing at const int.
    std::span<volatile int, 3> s3{varr};        // a span<volatile int> pointing at volatile int.
    std::span<const volatile int, 3> s4{cvarr}; // a span<const volatile int> pointing at const volatile int.
    assert(s1.size() + s2.size() + s3.size() + s4.size() == 12);
  }

  // types different (dynamic sized)
  {
    std::span<const int> s1{arr};           // a span<const int> pointing at int.
    std::span<volatile int> s2{arr};        // a span<volatile int> pointing at int.
    std::span<volatile int> s3{arr};        // a span<volatile int> pointing at const int.
    std::span<const volatile int> s4{arr};  // a span<const volatile int> pointing at int.
    std::span<const volatile int> s5{carr}; // a span<const volatile int> pointing at const int.
    std::span<const volatile int> s6{varr}; // a span<const volatile int> pointing at volatile int.
    assert(s1.size() + s2.size() + s3.size() + s4.size() + s5.size() + s6.size() == 18);
  }

  // types different (static sized)
  {
    std::span<const int, 3> s1{arr};           // a span<const int> pointing at int.
    std::span<volatile int, 3> s2{arr};        // a span<volatile int> pointing at int.
    std::span<volatile int, 3> s3{arr};        // a span<volatile int> pointing at const int.
    std::span<const volatile int, 3> s4{arr};  // a span<const volatile int> pointing at int.
    std::span<const volatile int, 3> s5{carr}; // a span<const volatile int> pointing at const int.
    std::span<const volatile int, 3> s6{varr}; // a span<const volatile int> pointing at volatile int.
    assert(s1.size() + s2.size() + s3.size() + s4.size() + s5.size() + s6.size() == 18);
  }
}

template <class T>
constexpr bool testSpan() {
  T val[2] = {};

  ASSERT_NOEXCEPT(std::span<T>{val});
  ASSERT_NOEXCEPT(std::span<T, 2>{val});
  ASSERT_NOEXCEPT(std::span<const T>{val});
  ASSERT_NOEXCEPT(std::span<const T, 2>{val});

  std::span<T> s1          = val;
  std::span<T, 2> s2       = val;
  std::span<const T> s3    = val;
  std::span<const T, 2> s4 = val;
  assert(s1.data() == val && s1.size() == 2);
  assert(s2.data() == val && s2.size() == 2);
  assert(s3.data() == val && s3.size() == 2);
  assert(s4.data() == val && s4.size() == 2);

  TEST_DIAGNOSTIC_PUSH
  TEST_CLANG_DIAGNOSTIC_IGNORED("-Wdangling")
  std::span<const int> s5    = {{1, 2}};
  std::span<const int, 2> s6 = {{1, 2}};
  assert(s5.size() == 2); // and it dangles
  assert(s6.size() == 2); // and it dangles
  TEST_DIAGNOSTIC_POP

  return true;
}

struct A {};

int main(int, char**) {
  testSpan<int>();
  testSpan<double>();
  testSpan<A>();
  testSpan<std::string>();

  static_assert(testSpan<int>());
  static_assert(testSpan<double>());
  static_assert(testSpan<A>());

  checkCV();

  // Size wrong
  {
    static_assert(!std::is_constructible_v<std::span<int, 2>, int (&)[3]>);
  }

  // Type wrong
  {
    static_assert(!std::is_constructible_v<std::span<float>, int (&)[3]>);
    static_assert(!std::is_constructible_v<std::span<float, 3>, int (&)[3]>);
  }

  // CV wrong (dynamically sized)
  {
    static_assert(!std::is_constructible_v<std::span<int>, const int (&)[3]>);
    static_assert(!std::is_constructible_v<std::span<int>, volatile int (&)[3]>);
    static_assert(!std::is_constructible_v<std::span<int>, const volatile int (&)[3]>);

    static_assert(!std::is_constructible_v<std::span<const int>, volatile int (&)[3]>);
    static_assert(!std::is_constructible_v<std::span<const int>, const volatile int (&)[3]>);

    static_assert(!std::is_constructible_v<std::span<volatile int>, const int (&)[3]>);
    static_assert(!std::is_constructible_v<std::span<volatile int>, const volatile int (&)[3]>);
  }

  // CV wrong (statically sized)
  {
    static_assert(!std::is_constructible_v<std::span<int, 3>, const int (&)[3]>);
    static_assert(!std::is_constructible_v<std::span<int, 3>, volatile int (&)[3]>);
    static_assert(!std::is_constructible_v<std::span<int, 3>, const volatile int (&)[3]>);

    static_assert(!std::is_constructible_v<std::span<const int, 3>, volatile int (&)[3]>);
    static_assert(!std::is_constructible_v<std::span<const int, 3>, const volatile int (&)[3]>);

    static_assert(!std::is_constructible_v<std::span<volatile int, 3>, const int (&)[3]>);
    static_assert(!std::is_constructible_v<std::span<volatile int, 3>, const volatile int (&)[3]>);
  }

  return 0;
}