[libcxx-commits] [libcxx] [libc++] Implement ranges::iota (PR #68494)

[nicole mazzuca via libcxx-commits]

================
@@ -0,0 +1,141 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+
+//  template <class O, class T>
+//    struct out_value_result;
+
+#include <algorithm>
+#include <cassert>
+#include <type_traits>
+
+#include "MoveOnly.h"
+
+using std::ranges::out_value_result;
+
+//
+// Helper structs
+//
+
+// only explicit construction
+struct IterTypeExplicit {
+  explicit IterTypeExplicit(int*);
+};
+
+// implicit construction
+struct IterTypeImplicit {
+  IterTypeImplicit(int*);
+};
+
+struct IterTypeImplicitRef {
+  IterTypeImplicitRef(int&);
+};
+
+struct NotConvertible {};
+
+template <class T>
+struct ConvertibleFrom {
+  constexpr ConvertibleFrom(T c) : content{c} {}
+  T content;
+};
+
+// Standard layout classes can't have virtual functions
+struct NonStandardLayoutTypeBase {
+  virtual ~NonStandardLayoutTypeBase();
+};
+struct NonStandardLayoutType : public NonStandardLayoutTypeBase {};
+
+//
+constexpr bool test_constraints() {
+  // requires convertible_to<const _OutIter1&, _OutIter2> && convertible_to<const _ValType1&, _ValType2>
+  static_assert(std::is_constructible_v<out_value_result<int*, int>, out_value_result<int*, int>>);
+
+  // test failure when implicit conversion isn't allowed
+  static_assert(!std::is_constructible_v<out_value_result<IterTypeExplicit, int>, out_value_result<int*, int>>);
+
+  // test success when implicit conversion is allowed, checking combinations of value, reference, and const
+  static_assert(std::is_constructible_v<out_value_result<IterTypeImplicit, int>, out_value_result<int*, int>>);
+  static_assert(std::is_constructible_v<out_value_result<IterTypeImplicit, int>, out_value_result<int*, int> const>);
+  static_assert(std::is_constructible_v<out_value_result<IterTypeImplicit, int>, out_value_result<int*, int>&>);
+  static_assert(std::is_constructible_v<out_value_result<IterTypeImplicit, int>, out_value_result<int*, int> const&>);
+
+  static_assert(!std::is_constructible_v<out_value_result<IterTypeImplicitRef, int>, out_value_result<int, int>&>);
+
+  // has to be convertible via const&
+  static_assert(std::is_convertible_v<out_value_result<int, int>&, out_value_result<long, long>>);
+  static_assert(std::is_convertible_v<const out_value_result<int, int>&, out_value_result<long, long>>);
+  static_assert(std::is_convertible_v<out_value_result<int, int>&&, out_value_result<long, long>>);
+  static_assert(std::is_convertible_v<const out_value_result<int, int>&&, out_value_result<long, long>>);
+
+  // should be move constructible
+  static_assert(std::is_move_constructible_v<out_value_result<MoveOnly, int>>);
+  static_assert(std::is_move_constructible_v<out_value_result<int, MoveOnly>>);
+
+  // conversions should not work if there is no conversion
+  static_assert(!std::is_convertible_v<out_value_result<NotConvertible, int>, out_value_result<int, NotConvertible>>);
+  static_assert(!std::is_convertible_v<out_value_result<int, NotConvertible>, out_value_result<NotConvertible, int>>);
+
+  // check standard layout
+  static_assert(std::is_standard_layout_v<out_value_result<int, int>>);
+  static_assert(!std::is_standard_layout_v<out_value_result<NonStandardLayoutType, int>>);
+
+  return true;
+}
+
+// Test results
+constexpr bool test() {
+  {
+    // Check that conversion operator works
+    out_value_result<double, int> res{10, 1};
+    assert(res.out == 10);
+    assert(res.value == 1);
+    out_value_result<ConvertibleFrom<double>, ConvertibleFrom<int>> res2 = res;
+    assert(res2.out.content == 10);
+    assert(res2.value.content == 1);
+  }
+  {
+    // Check that out_value_result isn't overconstrained w.r.t. move/copy constructors
+    out_value_result<MoveOnly, int> res{MoveOnly{}, 10};
+    assert(res.out.get() == 1);
+    assert(res.value == 10);
+    auto res2 = std::move(res);
+    assert(res.out.get() == 0);
+    assert(res.value == 10);
+    assert(res2.out.get() == 1);
+    assert(res2.value == 10);
+  }
+  {
+    // Check structured binding
+    auto [out, val] = out_value_result<int, int>{1, 2};
+    assert(out == 1);
+    assert(val == 2);
+  }
+  {
+    // Check default construction
+    out_value_result<int, double> res;
+    static_assert(std::is_same_v<int, decltype(res.out)>);
+    static_assert(std::is_same_v<double, decltype(res.value)>);
+  }
+  {
+    // Check aggregate initiazliation
+    out_value_result<int, int> res = {1, 2};
+    assert(res.out == 1);
+    assert(res.value == 2);
+  }
+
+  return true;
+}
+
+int main(int, char**) {
+  test_constraints();
+  static_assert(test_constraints());
+  test();
+  static_assert(test());
+  return 0;
+}
----------------
strega-nil wrote:

These tests seem good, but in a future PR it might be nice to centralize testing for all `_result` types (see also previous thought about centralizing the `_result` types' definitions).

No change requested.

https://github.com/llvm/llvm-project/pull/68494