Add basic unit test

Full tests are provided in the submodule - this checks that it compiles
and links correctly.

Author: thk123

CMakeLists.txt

@@ -113,6 +113,8 @@ if("${CMAKE_CXX_COMPILER_ID}" STREQUAL "Clang" OR
     endif()
 endif()
 
+add_subdirectory(lib/variant)
+
 add_subdirectory(src)
 add_subdirectory(regression)
 add_subdirectory(unit)

src/util/CMakeLists.txt

@@ -47,4 +47,4 @@ add_dependencies(util generate_version_cpp)
 
 generic_includes(util)
 
-target_link_libraries(util big-int langapi)
+target_link_libraries(util big-int langapi mpark_variant)

src/util/module_dependencies.txt

@@ -1,6 +1,8 @@
 big-int
 mach # system
 malloc # system
+mpark
 nonstd
 sys # system
 util
+

src/util/variant.h

@@ -0,0 +1,18 @@
+/*******************************************************************\
+
+Module: typedef for optional class template. To be replaced with
+        std::optional once C++17 support is enabled
+
+Author: Diffblue Ltd.
+
+\*******************************************************************/
+
+#ifndef CPROVER_UTIL_VARIANT_H
+#define CPROVER_UTIL_VARIANT_H
+
+#include <mpark/variant.hpp>
+
+template <typename ... Ts>
+using variantt = mpark::variant<Ts...>;
+
+#endif // CPROVER_UTIL_VARIANT_H

unit/util/variant.cpp

@@ -0,0 +1,12 @@
+// Copyright 2016-2019 Diffblue Limited. All Rights Reserved.
+
+#include <testing-utils/use_catch.h>
+#include <util/variant.h>
+
+TEST_CASE("Ensure variant has been included", "[core][util][variant]")
+{
+  variantt<int, float> some_type = 1;
+  REQUIRE(some_type.index() == 0);
+  some_type = 1.0f;
+  REQUIRE(some_type.index() == 1);
+}