Feat: modernize CMake files

CMakeLists.txt

@@ -2,39 +2,66 @@
 # Distributed under the Boost Software License, Version 1.0.
 # See accompanying file LICENSE_1_0.txt or copy at https://www.boost.org/LICENSE_1_0.txt
 
-cmake_minimum_required( VERSION 3.5...3.31 )
-project( boost_any VERSION "${BOOST_SUPERPROJECT_VERSION}" LANGUAGES CXX )
+cmake_minimum_required(VERSION 3.21...4.2)
+project(boost_any VERSION "${BOOST_SUPERPROJECT_VERSION}" LANGUAGES CXX)
 
-if (BOOST_USE_MODULES)
+if(BOOST_USE_MODULES)
     add_library(boost_any)
-    target_sources(boost_any PUBLIC
-        FILE_SET modules_public TYPE CXX_MODULES FILES
-            ${CMAKE_CURRENT_LIST_DIR}/modules/boost_any.cppm
+    target_sources(
+        boost_any
+        PUBLIC
+            FILE_SET modules_public
+                TYPE CXX_MODULES
+                FILES ${CMAKE_CURRENT_LIST_DIR}/modules/boost_any.cppm
     )
 
     target_compile_features(boost_any PUBLIC cxx_std_20)
     target_compile_definitions(boost_any PUBLIC BOOST_USE_MODULES)
-    if (CMAKE_CXX_COMPILER_IMPORT_STD)
+    if(${CMAKE_CXX_STANDARD} IN_LIST CMAKE_CXX_COMPILER_IMPORT_STD)
+        set(CMAKE_CXX_MODULE_STD ON)
         target_compile_definitions(boost_any PRIVATE BOOST_ANY_USE_STD_MODULE)
         message(STATUS "Using `import std;`")
     else()
-        message(STATUS "`import std;` is not available")
+        message(WARNING "`import std;` is not available")
     endif()
     set(__scope PUBLIC)
+
+    add_executable(module_sample modules/usage_sample.cpp)
+    target_link_libraries(module_sample PRIVATE boost_any)
 else()
+    set(CMAKE_VERIFY_INTERFACE_HEADER_SETS ON)
     add_library(boost_any INTERFACE)
     set(__scope INTERFACE)
 endif()
 
-target_include_directories(boost_any ${__scope} include)
-target_link_libraries( boost_any
+if(CMAKE_SKIP_INSTALL_RULES OR PROJECT_IS_TOP_LEVEL)
+    target_sources(
+        boost_any
+        ${__scope}
+        FILE_SET headers_public
+        TYPE HEADERS
+        BASE_DIRS include
+        FILES
+            include/boost/any/bad_any_cast.hpp
+            include/boost/any/basic_any.hpp
+            include/boost/any/fwd.hpp
+            include/boost/any/unique_any.hpp
+            include/boost/any/detail/config.hpp
+            include/boost/any/detail/placeholder.hpp
+    )
+else()
+    target_include_directories(boost_any ${__scope} include)
+endif()
+
+target_link_libraries(
+    boost_any
     ${__scope}
         Boost::config
         Boost::throw_exception
         Boost::type_index
 )
 
-add_library( Boost::any ALIAS boost_any )
+add_library(Boost::any ALIAS boost_any)
 
 if(BUILD_TESTING)
     add_subdirectory(test)

include/boost/any/fwd.hpp

@@ -17,6 +17,9 @@
 #ifdef BOOST_HAS_PRAGMA_ONCE
 # pragma once
 #endif
+
+#include <type_traits>
+
 #endif  // #ifndef BOOST_ANY_INTERFACE_UNIT
 
 /// \file boost/any/fwd.hpp

modules/boost_any.cppm

@@ -11,7 +11,9 @@ module;
 #include <boost/assert.hpp>
 #include <boost/config.hpp>
 #include <boost/throw_exception.hpp>
-#include <boost/type_index.hpp>
+
+// FIXME(CK): #include <boost/type_index.hpp>
+import boost.type_index;
 
 #ifdef BOOST_ANY_USE_STD_MODULE
 import std;

modules/usage_sample.cpp

@@ -7,10 +7,46 @@
 // clang++ -std=c++20 -fmodule-file=type_index.pcm type_index.pcm usage_sample.cpp
 
 //[any_module_example
+
+#ifdef BOOST_ANY_USE_STD_MODULE
+import std;
+#else
+# include <sstream>
+# include <string>
+# include <print>
+#endif
+
 import boost.any;
 
-int main() {
-    boost::any a = 42;
+namespace {
+
+    template <typename... Ts> auto any_to_string(const boost::any& a) -> std::string {
+        std::ostringstream oss;
+
+        auto try_cast = [&](auto* dummy) -> bool {
+            using T = std::decay_t<decltype(*dummy)>;
+            if (a.type() == typeid(T)) {
+                oss << boost::any_cast<T>(a);
+                return true;
+            }
+            return false;
+        };
+
+        // Expand over Ts...
+        bool const success = (try_cast((Ts*)nullptr) || ...);
+
+        if (!success) {
+            oss << "<unknown type: " << a.type().name() << ">";
+        }
+        return oss.str();
+    }
+
+}  // namespace
+
+// Usage:
+auto main() -> int {
+    boost::any const a = 42;
+    std::println(stdout, "{}", any_to_string<int, double, std::string>(a));
 }
 //]