switch from std expected to tl expected

CMakeLists.txt

@@ -36,6 +36,13 @@ FetchContent_Declare(
     GIT_SHALLOW     TRUE
 )
 
+FetchContent_Declare(
+    tl_expected
+    GIT_REPOSITORY https://github.com/TartanLlama/expected.git
+    GIT_TAG v1.1.0
+)
+FetchContent_MakeAvailable(tl_expected)
+
 # c++20 format library, super usefull, super fast
 set(FMT_TEST OFF CACHE INTERNAL "disabling fmt tests")
 set(FMT_FUZZ OFF CACHE INTERNAL "disabling fmt fuzz")
@@ -43,7 +50,7 @@ FetchContent_Declare(fmt
     URL     https://github.com/fmtlib/fmt/archive/refs/tags/10.2.1.zip
     URL_MD5 1bba4e8bdd7b0fa98f207559ffa380a3
 )
-FetchContent_MakeAvailable(fmt spdlog)
+FetchContent_MakeAvailable(fmt spdlog tl_expected)
 
 include_directories(${CMAKE_CURRENT_SOURCE_DIR})
 # add_compile_definitions(BOOST_ASIO_ENABLE_HANDLER_TRACKING)

config.hpp

@@ -4,16 +4,34 @@
 #include <boost/system/errc.hpp>
 #include <boost/system/error_code.hpp>
 
+#if __has_include(<expected>)
 #include <expected>
+#elif __has_include(<tl/expected.hpp>)
+#include <tl/expected.hpp>
+#else
+#error "No expected implementation available"
+#endif
 
 namespace ranczo {
 
+#if __has_include(<expected>)
 template < typename T >
 using expected = std::expected< T, boost::system::error_code >;
-
 template < typename T >
 using unexpected = std::unexpected< T >;
 
+#elif __has_include(<tl/expected.hpp>)
+template < typename T >
+using expected = tl::expected< T, boost::system::error_code >;
+
+template < typename T >
+using unexpected = tl::unexpected< T >;
+
+#else
+#error "No expected implementation available"
+#endif
+
+
 template < typename T >
 using awaitable_expected = boost::asio::awaitable< expected< T > >;