diff --git a/include/core.hpp b/include/core.hpp
index edd3281..20e8b1e 100644
--- a/include/core.hpp
+++ b/include/core.hpp
@@ -73,6 +73,7 @@ namespace riddle
      * @return std::shared_ptr<arith_item> The int expression.
      */
     [[nodiscard]] virtual std::shared_ptr<arith_item> new_int() = 0;
+
     /**
      * @brief Create a new int expression with a value.
      *
diff --git a/include/declaration.hpp b/include/declaration.hpp
index 3fbb3cb..f476721 100644
--- a/include/declaration.hpp
+++ b/include/declaration.hpp
@@ -153,8 +153,8 @@ namespace riddle
 
   private:
     std::vector<std::pair<std::vector<id_token>, id_token>> parameters; // the parameters of the constructor..
-    std::vector<init_element> inits;                                      // the initializations of the fields..
-    std::vector<std::unique_ptr<statement>> body;                         // the body of the constructor..
+    std::vector<init_element> inits;                                    // the initializations of the fields..
+    std::vector<std::unique_ptr<statement>> body;                       // the body of the constructor..
   };
 
   class method_declaration
@@ -191,10 +191,10 @@ namespace riddle
     void refine(scope &scp) const;
 
   private:
-    std::vector<id_token> return_type;                                    // the return type of the method..
-    id_token name;                                                        // the name of the method..
+    std::vector<id_token> return_type;                                  // the return type of the method..
+    id_token name;                                                      // the name of the method..
     std::vector<std::pair<std::vector<id_token>, id_token>> parameters; // the parameters of the method..
-    std::vector<std::unique_ptr<statement>> body;                         // the body of the method..
+    std::vector<std::unique_ptr<statement>> body;                       // the body of the method..
   };
 
   class predicate_declaration
@@ -238,10 +238,10 @@ namespace riddle
     void refine(scope &scp) const;
 
   private:
-    id_token name;                                                        // the name of the class..
+    id_token name;                                                      // the name of the class..
     std::vector<std::pair<std::vector<id_token>, id_token>> parameters; // the type parameters of the class..
-    std::vector<std::vector<id_token>> base_predicates;                   // the base predicates of the class..
-    std::vector<std::unique_ptr<statement>> body;                         // the body of the rule..
+    std::vector<std::vector<id_token>> base_predicates;                 // the base predicates of the class..
+    std::vector<std::unique_ptr<statement>> body;                       // the body of the rule..
   };
 
   class class_declaration final : public type_declaration
diff --git a/src/constructor.cpp b/src/constructor.cpp
index 1a8ce25..de2a03d 100644
--- a/src/constructor.cpp
+++ b/src/constructor.cpp
@@ -56,8 +56,10 @@ namespace riddle
                         arguments.push_back(xpr);
                     }
 
-                    if (auto c = tp->get_constructor(arg_types))
-                        instance->items.emplace(init.get_name().id, c->get().invoke(std::move(arguments)));
+                    if (arg_types.size() == 1 && f->get().get_type().is_assignable_from(arg_types.at(0)))
+                        instance->items.emplace(init.get_name().id, arguments.at(0)); // we assign the argument to the field
+                    else if (auto c = tp->get_constructor(arg_types))
+                        instance->items.emplace(init.get_name().id, c->get().invoke(std::move(arguments))); // we invoke the constructor and assign the result to the field
                     else
                         throw std::runtime_error("Cannot find constructor for class " + init.get_name().id);
                 }
diff --git a/src/parser.cpp b/src/parser.cpp
index 19f5fae..f6c530a 100644
--- a/src/parser.cpp
+++ b/src/parser.cpp
@@ -296,7 +296,7 @@ namespace riddle
                 error("expected either `typedef` or `enum` or `class` or `predicate` or `void` or identifier..");
             }
 
-        if (constructors.empty())
+        if (constructors.empty()) // if there are no constructors, we add the default constructor..
         {
             std::vector<std::pair<std::vector<id_token>, id_token>> parameters; // the parameters of the constructor..
             std::vector<init_element> inits;                                    // the initializations of the fields..