properly deallocating the prefix obeject

src/ast/expressions/prefix.cpp

@@ -16,4 +16,8 @@ namespace ast {
     std::string prefix_expr::str() const {
         return token.literal + right->str();
     }
+
+    prefix_expr::~prefix_expr() {
+        delete right;
+    };
 } // namespace ast

src/ast/expressions/prefix.hpp

@@ -12,5 +12,6 @@ namespace ast {
 
         std::string token_literal() const override;
         std::string str() const override;
+        ~prefix_expr();
     };
 } // namespace ast