Add -Wnon-virtual-dtor

CMakeLists.txt

@@ -361,6 +361,7 @@ else()
       -Wextra-semi
       -Werror=shadow
       -fsigned-char
+      -Wnon-virtual-dtor
 
       $<$<CXX_COMPILER_ID:CLANG>:
         $<$<VERSION_GREATER:$<CXX_COMPILER_VERSION>,3.8>:

src/namer.h

@@ -108,6 +108,8 @@ class Namer {
   Namer(Config config, std::set<std::string> keywords)
       : config_(config), keywords_(std::move(keywords)) {}
 
+  virtual ~Namer() {}
+
   template<typename T> std::string Method(const T &s) const {
     return Method(s.name);
   }