Implement option explicit for dynamic objects.

Closes #218

cheatsheet.md

@@ -354,6 +354,18 @@ o.f = fun(y) { print(this.x + y); }
 o.f(10); // prints 13
 ```
 
+### Option Explicit
+
+If you want to disable dynamic parameter definitions, you can `set_explicit`.
+
+```
+class My_Class {
+  def My_Class() {
+    this.set_explicit(true);
+    this.x = 2; // this would fail with explicit set to true
+  }
+};
+
 ## method_missing
 
 A function of the signature `method_missing(object, name, param1, param2, param3)` will be called if an appropriate

include/chaiscript/dispatchkit/dispatchkit.hpp

@@ -1002,12 +1002,17 @@ namespace chaiscript
             }();
 
             if (!functions.empty()) {
-              if (is_no_param) {
-                std::vector<Boxed_Value> tmp_params(params);
-                tmp_params.insert(tmp_params.begin() + 1, var(t_name));
-                return do_attribute_call(2, tmp_params, functions, m_conversions);
-              } else {
-                return dispatch::dispatch(functions, {params[0], var(t_name), var(std::vector<Boxed_Value>(params.begin()+1, params.end()))}, m_conversions);
+              try {
+                if (is_no_param) {
+                  std::vector<Boxed_Value> tmp_params(params);
+                  tmp_params.insert(tmp_params.begin() + 1, var(t_name));
+                  return do_attribute_call(2, tmp_params, functions, m_conversions);
+                } else {
+                  return dispatch::dispatch(functions, {params[0], var(t_name), var(std::vector<Boxed_Value>(params.begin()+1, params.end()))}, m_conversions);
+                }
+              } catch (const dispatch::option_explicit_set &e) {
+                throw chaiscript::exception::dispatch_error(params, std::vector<Const_Proxy_Function>(funs.second->begin(), funs.second->end()), 
+                    e.what());
               }
             }
 

include/chaiscript/dispatchkit/dynamic_object.hpp

@@ -24,6 +24,16 @@ namespace chaiscript
 {
   namespace dispatch
   {
+    struct option_explicit_set : std::runtime_error {
+      option_explicit_set(const std::string &t_param_name)
+        : std::runtime_error("option explicit set and parameter '" + t_param_name + "' does not exist")
+      {
+
+      }
+
+      virtual ~option_explicit_set() CHAISCRIPT_NOEXCEPT {}
+    };
+
     class Dynamic_Object
     {
       public:
@@ -79,11 +89,19 @@ namespace chaiscript
 
         Boxed_Value &method_missing(const std::string &t_method_name)
         {
+          if (m_option_explicit && m_attrs.find(t_method_name) == m_attrs.end()) {
+            throw option_explicit_set(t_method_name);
+          }
+
           return get_attr(t_method_name);
         }
 
         const Boxed_Value &method_missing(const std::string &t_method_name) const
         {
+          if (m_option_explicit && m_attrs.find(t_method_name) == m_attrs.end()) {
+            throw option_explicit_set(t_method_name);
+          }
+
           return get_attr(t_method_name);
         }
 

include/chaiscript/dispatchkit/proxy_functions.hpp

@@ -760,6 +760,14 @@ namespace chaiscript
         {
         }
 
+        dispatch_error(std::vector<Boxed_Value> t_parameters, 
+            std::vector<Const_Proxy_Function> t_functions,
+            const std::string &t_desc)
+          : std::runtime_error(t_desc), parameters(std::move(t_parameters)), functions(std::move(t_functions))
+        {
+        }
+
+
         dispatch_error(const dispatch_error &) = default;
         virtual ~dispatch_error() CHAISCRIPT_NOEXCEPT {}