Enable building phasar with C++20 (#618)

Author: fabianbs96

CMakeLists.txt

@@ -10,8 +10,15 @@ if (NOT PHASAR_IN_TREE)
   set(CMAKE_PROJECT_NAME "phasar")
 endif ()
 
+option(PHASAR_EXPERIMENTAL_CXX20 "Build phasar in C++20 mode. THis is an experimental feature" OFF)
+
 set(CMAKE_EXPORT_COMPILE_COMMANDS YES)
-set(CMAKE_CXX_STANDARD 17)
+if(PHASAR_EXPERIMENTAL_CXX20)
+  message(STATUS "Selected experimental C++ build")
+  set(CMAKE_CXX_STANDARD 20)
+else()
+  set(CMAKE_CXX_STANDARD 17)
+endif()
 set(CMAKE_CXX_STANDARD_REQUIRED ON)
 set(CMAKE_CXX_EXTENSIONS OFF)
 

include/phasar/DataFlow/IfdsIde/EdgeFunction.h

@@ -222,10 +222,8 @@ class [[clang::trivial_abi]] EdgeFunction final : EdgeFunctionBase {
 
   /// Implicit-conversion constructor from EdgeFunctionRef. Increments the
   /// ref-count if not small-object optimized
-  template <typename ConcreteEF,
-            typename = std::enable_if_t<
-                !std::is_same_v<EdgeFunction, std::decay_t<ConcreteEF>> &&
-                IsEdgeFunction<ConcreteEF>>>
+  template <typename ConcreteEF, typename = std::enable_if_t<!std::is_same_v<
+                                     EdgeFunction, std::decay_t<ConcreteEF>>>>
   EdgeFunction(EdgeFunctionRef<ConcreteEF> CEF) noexcept
       : EdgeFunction(CEF.Instance,
                      {&VTableFor<ConcreteEF>, [CEF] {