Look for and optimize decl assignments

Re: #356

include/chaiscript/language/chaiscript_common.hpp

@@ -62,7 +62,7 @@ namespace chaiscript
 
 
   /// Types of AST nodes available to the parser and eval
-  enum class AST_Node_Type { Id, Fun_Call, Unused_Return_Fun_Call, Arg_List, Equation, Var_Decl,
+  enum class AST_Node_Type { Id, Fun_Call, Unused_Return_Fun_Call, Arg_List, Equation, Var_Decl, Assign_Decl,
     Array_Call, Dot_Access,
     Lambda, Block, Scopeless_Block, Def, While, If, For, Ranged_For, Inline_Array, Inline_Map, Return, File, Prefix, Break, Continue, Map_Pair, Value_Range,
     Inline_Range, Try, Catch, Finally, Method, Attr_Decl,  
@@ -77,7 +77,7 @@ namespace chaiscript
   {
     /// Helper lookup to get the name of each node type
     inline const char *ast_node_type_to_string(AST_Node_Type ast_node_type) {
-      static const char * const ast_node_types[] = { "Id", "Fun_Call", "Unused_Return_Fun_Call", "Arg_List", "Equation", "Var_Decl",
+      static const char * const ast_node_types[] = { "Id", "Fun_Call", "Unused_Return_Fun_Call", "Arg_List", "Equation", "Var_Decl", "Assign_Decl",
                                     "Array_Call", "Dot_Access", 
                                     "Lambda", "Block", "Scopeless_Block", "Def", "While", "If", "For", "Ranged_For", "Inline_Array", "Inline_Map", "Return", "File", "Prefix", "Break", "Continue", "Map_Pair", "Value_Range",
                                     "Inline_Range", "Try", "Catch", "Finally", "Method", "Attr_Decl",

include/chaiscript/language/chaiscript_eval.hpp

@@ -555,6 +555,27 @@ namespace chaiscript
         }
     };
 
+    template<typename T>
+    struct Assign_Decl_AST_Node final : AST_Node_Impl<T> {
+        Assign_Decl_AST_Node(std::string t_ast_node_text, Parse_Location t_loc, std::vector<AST_Node_Impl_Ptr<T>> t_children) :
+          AST_Node_Impl<T>(std::move(t_ast_node_text), AST_Node_Type::Assign_Decl, std::move(t_loc), std::move(t_children)) { }
+
+        Boxed_Value eval_internal(const chaiscript::detail::Dispatch_State &t_ss) const override {
+          const std::string &idname = this->children[0]->text;
+
+          try {
+            Boxed_Value bv(detail::clone_if_necessary(this->children[1]->eval(t_ss), m_loc, t_ss));
+            bv.reset_return_value();
+            t_ss.add_object(idname, bv);
+            return bv;
+          } catch (const exception::name_conflict_error &e) {
+            throw exception::eval_error("Variable redefined '" + e.name() + "'");
+          }
+        }
+      private:
+        mutable std::atomic_uint_fast32_t m_loc = {0};
+    };
+
 
     template<typename T>
     struct Array_Call_AST_Node final : AST_Node_Impl<T> {

include/chaiscript/language/chaiscript_optimizer.hpp

@@ -97,7 +97,7 @@ namespace chaiscript {
     template<typename T>
     bool contains_var_decl_in_scope(const eval::AST_Node_Impl<T> &node)
     {
-      if (node.identifier == AST_Node_Type::Var_Decl) {
+      if (node.identifier == AST_Node_Type::Var_Decl || node.identifier == AST_Node_Type::Assign_Decl) {
         return true;
       }
 
@@ -208,6 +208,27 @@ namespace chaiscript {
         }
     };
 
+    struct Assign_Decl {
+      template<typename T>
+      auto optimize(eval::AST_Node_Impl_Ptr<T> node) {
+        if ((node->identifier == AST_Node_Type::Equation)
+             && node->text == "="
+             && node->children.size() == 2
+             && node->children[0]->identifier == AST_Node_Type::Var_Decl
+           )
+        {
+          std::vector<eval::AST_Node_Impl_Ptr<T>> new_children;
+          new_children.push_back(std::move(node->children[0]->children[0]));
+          new_children.push_back(std::move(node->children[1]));
+          return chaiscript::make_unique<eval::AST_Node_Impl<T>, eval::Assign_Decl_AST_Node<T>>(node->text, 
+              node->location, std::move(new_children) );
+        }
+
+        return node;
+      }
+    };
+
+
     struct If {
       template<typename T>
       auto optimize(eval::AST_Node_Impl_Ptr<T> node) {
@@ -440,7 +461,7 @@ namespace chaiscript {
     };
 
     typedef Optimizer<optimizer::Partial_Fold, optimizer::Unused_Return, optimizer::Constant_Fold, 
-      optimizer::If, optimizer::Return, optimizer::Dead_Code, optimizer::Block, optimizer::For_Loop> Optimizer_Default; 
+      optimizer::If, optimizer::Return, optimizer::Dead_Code, optimizer::Block, optimizer::For_Loop, optimizer::Assign_Decl> Optimizer_Default; 
 
   }
 }