Own implementation of std::tuple with reduced functionality

To reduce compile time.

src/blackmisc/tuple.h

@@ -0,0 +1,50 @@
+/* Copyright (C) 2021
+ * swift Project Community / Contributors
+ *
+ * This file is part of swift project. It is subject to the license terms in the LICENSE file found in the top-level
+ * directory of this distribution. No part of swift project, including this file, may be copied, modified, propagated,
+ * or distributed except according to the terms contained in the LICENSE file.
+ */
+
+//! \file
+
+#ifndef BLACKMISC_TUPLE_H
+#define BLACKMISC_TUPLE_H
+
+#include <utility>
+#include <stddef.h>
+
+//! \cond
+namespace BlackMisc::Private
+{
+    /*
+     * Own minimal implementation of std::tuple with very limited functionality.
+     * Only used to reduce compile time for the metaclass system.
+     */
+
+    template <size_t I, typename T>
+    struct tuple_part
+    {
+        T value;
+    };
+
+    template <typename...>
+    struct tuple_impl;
+
+    template <size_t... Is, typename... Ts>
+    struct tuple_impl<std::index_sequence<Is...>, Ts...> : public tuple_part<Is, Ts>...
+    {
+        template <typename F>
+        void for_each(F &&visitor) const
+        {
+            (static_cast<void>(visitor(static_cast<const tuple_part<Is, Ts>&>(*this).value)), ...);
+        }
+    };
+
+    template <typename... Ts>
+    struct tuple : public tuple_impl<std::make_index_sequence<sizeof...(Ts)>, Ts...>
+    {};
+}
+//! \endcond
+
+#endif