feat: Add an exception-less factory type and concept

sources.cmake

@@ -19,6 +19,7 @@ dplx_target_sources(concrete
         cncr/type_utils
         cncr/utils
         cncr/uuid
+        make
         overloaded
         scope_guard
 )

src/dplx/make.hpp

@@ -0,0 +1,36 @@
+
+// Copyright 2022-2023 Henrik Steffen Gaßmann
+//
+// Distributed under the Boost Software License, Version 1.0.
+//         (See accompanying file LICENSE or copy at
+//           https://www.boost.org/LICENSE_1_0.txt)
+
+#pragma once
+
+#include <concepts>
+#include <type_traits>
+
+#include <dplx/cncr/disappointment.hpp>
+
+namespace dplx
+{
+
+template <typename T>
+struct make
+{
+};
+
+// clang-format off
+template <typename T>
+concept makable
+    = requires {
+        typename T;
+        typename make<T>;
+    }                            
+    && std::movable<T>
+    && requires(make<T> const maker) {
+        { maker() } noexcept -> cncr::tryable_result<T>;
+    };
+// clang-format on
+
+} // namespace dplx

src/dplx/make.test.cpp

@@ -0,0 +1,43 @@
+
+// Copyright 2022-2023 Henrik Steffen Gaßmann
+//
+// Distributed under the Boost Software License, Version 1.0.
+//         (See accompanying file LICENSE or copy at
+//           https://www.boost.org/LICENSE_1_0.txt)
+
+#include "dplx/make.hpp"
+
+#include "test_utils.hpp"
+
+namespace cncr_tests
+{
+
+class myhandle
+{
+private:
+    constexpr myhandle() noexcept = default;
+
+public:
+    static auto my() noexcept -> result<myhandle>
+    {
+        return myhandle{};
+    }
+};
+
+} // namespace cncr_tests
+
+template <>
+struct dplx::make<cncr_tests::myhandle>
+{
+    auto operator()() const noexcept -> result<cncr_tests::myhandle>
+    {
+        return cncr_tests::myhandle::my();
+    }
+};
+
+namespace cncr_tests
+{
+
+static_assert(makable<myhandle>);
+
+}