Remove optional template with cpp_entity

Sam was having issues getting this to compile. I had similar issues once
I tried to compile in CentOS 7. The errors are related to cpp_entity
being a virtual base class that can't be inside a template.

src/asgn2/buildlist.hpp

@@ -2,26 +2,28 @@
 #define __CSE3150_TESTING_BUILDLIST_H
 
 #include <algorithm>
+#include <cppast/cpp_entity.hpp>
 #include <cppast/cpp_function.hpp>
 #include <cppast/cpp_template.hpp>
 #include <cppast/cpp_type.hpp>
 #include <cppast/libclang_parser.hpp>
 #include <cppast/visitor.hpp>
-#include <optional.hpp>
 
-tl::optional<const cppast::cpp_entity&> find_build_list_fn(const cppast::cpp_file& file) {
-  tl::optional<const cppast::cpp_entity&> result = tl::nullopt;
+// It'd be better to return an optional cpp_entity, but this breaks on some
+// compilers.
+const cppast::cpp_entity* find_build_list_fn(const cppast::cpp_file& file) {
+  const cppast::cpp_entity* result = nullptr;
 
   cppast::visit(file, [&](const cppast::cpp_entity& e, cppast::visitor_info info) {
     const auto is_function = e.kind() == cppast::cpp_entity_kind::function_t;
     const auto correct_name = e.name() == "buildList";
 
     if (is_function && correct_name) {
-      result = e;
+      result = &e;
     }
 
     // Stop visiting further nodes if we found the one we're looking for.
-    const auto should_keep_looking = result == tl::nullopt;
+    const auto should_keep_looking = result == nullptr;
     return should_keep_looking;
   });
 

src/asgn2/tests.cpp

@@ -46,13 +46,13 @@ TEST_CASE("Assignment 2") {
       }
 
       const auto build_list = find_build_list_fn(*w_list_file);
-      if (!build_list.has_value()) {
+      if (build_list == nullptr) {
         FAIL("Make sure the \"buildList\" function exists in \"asgn2/q1/WList.cpp\"");
       }
 
       // Ew... casting. (The first-party example uses it too, so this may be
         // required by the cppast API design.)
-      auto& build_list_fn = static_cast<const cppast::cpp_function&>(*build_list);
+      auto& build_list_fn = *static_cast<const cppast::cpp_function*>(build_list);
 
       if (question.id == "q1" || question.id == "q3") {
         INFO("\"buildList\" needs to take an \"std::list\" as a reference for q1.\"");