diff --git a/Makefile b/Makefile
index f50091d..52c646b 100644
--- a/Makefile
+++ b/Makefile
@@ -13,7 +13,7 @@ build:
 
 # 运行目标，运行生成的可执行文件
 run:
-	@cd $(BUILD_DIR) && ./zmxcc /dev/stdin -o /dev/null
+	@cd $(BUILD_DIR) && ./zmxcc /dev/stdin -o /dev/null 2>/dev/null
 
 # 清理目标
 clean:
diff --git a/include/ast/astnode.h b/include/ast/astnode.h
index fbd9e97..2411067 100644
--- a/include/ast/astnode.h
+++ b/include/ast/astnode.h
@@ -4,15 +4,11 @@
 #include <variant>
 #include <vector>
 #include "../semantic/visitor.h"
+#include "scope.hpp"
 #include "tools.h"
-using IdentifierType = std::string;
-struct ArrayType {
-  bool has_base_type;
-  IdentifierType basetype;
-  size_t level;
-};
-using ExprTypeInfo = std::variant<IdentifierType, ArrayType>;
 class ASTNodeVisitorBase {
+  friend Visitor;
+
  public:
   virtual ~ASTNodeVisitorBase() = default;
   virtual void visit(class ASTNodeBase *context) = 0;
@@ -20,6 +16,9 @@ class ASTNodeVisitorBase {
 
 class ASTNodeBase {
   friend Visitor;
+
+ protected:
+  std::shared_ptr<ScopeBase> current_scope;
   ASTNodeType type;
   // std::vector<std::shared_ptr<ASTNodeBase>> children;
   size_t start_line, start_char_pos, end_line, end_char_pos;
diff --git a/include/ast/scope.hpp b/include/ast/scope.hpp
new file mode 100644
index 0000000..aa3a57b
--- /dev/null
+++ b/include/ast/scope.hpp
@@ -0,0 +1,165 @@
+#pragma once
+#include <memory>
+#include <stdexcept>
+#include <string>
+#include <unordered_map>
+#include <unordered_set>
+#include <vector>
+#include "tools.h"
+class ScopeBase {
+  friend class Visitor;
+  friend class LocalScope;
+  friend class MemberFunctionScope;
+  friend class FunctionScope;
+  friend class ClassDefScope;
+  friend class GlobalScope;
+
+ protected:
+  ScopeBase *parent;  // cannot use std::shared_ptr<ScopeBase> because of circular dependency
+  virtual bool VariableNameAvailable(const std::string &name, int ttl) = 0;
+  virtual bool add_variable(const std::string &name, const ExprTypeInfo &type) = 0;
+  static inline bool IsKeyWord(const std::string &name) {
+    static const std::unordered_set<std::string> keywords = {"void", "bool",  "int",   "string",   "new",   "class",
+                                                             "null", "true",  "false", "this",     "if",    "else",
+                                                             "for",  "while", "break", "continue", "return"};
+    return keywords.find(name) != keywords.end();
+  }
+};
+class LocalScope : public ScopeBase {
+  friend class Visitor;
+  std::unordered_map<std::string, ExprTypeInfo> local_variables;
+  bool add_variable(const std::string &name, const ExprTypeInfo &type) override {
+    if (!VariableNameAvailable(name, 0)) {
+      throw std::runtime_error("Variable name " + name + " is not available");
+    }
+    local_variables[name] = type;
+    return true;
+  }
+  bool VariableNameAvailable(const std::string &name, int ttl) override {
+    if (ttl == 0 && IsKeyWord(name)) {
+      return false;
+    }
+    if (ttl == 0) {
+      if (local_variables.find(name) != local_variables.end()) {
+        return false;
+      }
+    }
+    return parent->VariableNameAvailable(name, ttl + 1);
+  }
+};
+struct FunctionSchema {
+  friend class Visitor;
+  ExprTypeInfo return_type;
+  std::vector<std::pair<ExprTypeInfo, std::string>> arguments;
+};
+class FunctionScope : public ScopeBase {
+  friend class Visitor;
+  FunctionSchema schema;
+  bool add_variable([[maybe_unused]] const std::string &name, [[maybe_unused]] const ExprTypeInfo &type) override {
+    throw std::runtime_error("FunctionScope does not support add_variable");
+  }
+  bool VariableNameAvailable(const std::string &name, int ttl) override {
+    if (ttl == 0 && IsKeyWord(name)) {
+      return false;
+    }
+    if (ttl == 1) {
+      for (const auto &arg : schema.arguments) {
+        if (arg.second == name) {
+          return false;
+        }
+      }
+    }
+    return parent->VariableNameAvailable(name, ttl + 1);
+  }
+};
+class ClassDefScope : public ScopeBase {
+  friend class Visitor;
+  std::unordered_map<std::string, ExprTypeInfo> member_variables;
+  std::unordered_map<std::string, std::shared_ptr<FunctionScope>> member_functions;
+  bool add_variable(const std::string &name, const ExprTypeInfo &type) override {
+    if (!VariableNameAvailable(name, 0)) {
+      throw std::runtime_error("Variable name " + name + " is not available");
+    }
+    member_variables[name] = type;
+    return true;
+  }
+  bool add_function(const std::string &name, std::shared_ptr<FunctionScope> ptr) {
+    if (IsKeyWord(name)) return false;
+    if (member_variables.find(name) != member_variables.end()) {
+      return false;
+    }
+    if (member_functions.find(name) != member_functions.end()) {
+      return false;
+    }
+    member_functions[name] = ptr;
+    return true;
+  }
+  bool VariableNameAvailable(const std::string &name, int ttl) override {
+    if (ttl == 0 && IsKeyWord(name)) {
+      return false;
+    }
+    if (member_functions.find(name) != member_functions.end()) {
+      return false;
+    }
+    return parent->VariableNameAvailable(name, ttl + 1);
+  }
+};
+class GlobalScope : public ScopeBase {
+  friend class Visitor;
+  std::unordered_map<std::string, ExprTypeInfo> global_variables;
+  std::unordered_map<std::string, std::shared_ptr<FunctionScope>> global_functions;
+  std::unordered_map<std::string, std::shared_ptr<ClassDefScope>> classes;
+  bool add_class(const std::string &name, std::shared_ptr<ClassDefScope> ptr) {
+    if (IsKeyWord(name)) return false;
+    if (classes.find(name) != classes.end()) {
+      return false;
+    }
+    if (global_functions.find(name) != global_functions.end()) {
+      return false;
+    }
+    if (global_variables.find(name) != global_variables.end()) {
+      return false;
+    }
+    classes[name] = ptr;
+    return true;
+  }
+  bool add_function(const std::string &name, std::shared_ptr<FunctionScope> ptr) {
+    if (IsKeyWord(name)) return false;
+    if (classes.find(name) != classes.end()) {
+      return false;
+    }
+    if (global_functions.find(name) != global_functions.end()) {
+      return false;
+    }
+    if (global_variables.find(name) != global_variables.end()) {
+      return false;
+    }
+    global_functions[name] = ptr;
+    return true;
+  }
+  bool add_variable(const std::string &name, const ExprTypeInfo &type) override {
+    if (!VariableNameAvailable(name, 0)) {
+      throw std::runtime_error("Variable name " + name + " is not available");
+    }
+    global_variables[name] = type;
+    return true;
+  }
+  bool VariableNameAvailable(const std::string &name, [[maybe_unused]] int ttl) override {
+    if (ttl == 0 && IsKeyWord(name)) {
+      return false;
+    }
+    if (global_variables.find(name) != global_variables.end()) {
+      return false;
+    }
+    if (classes.find(name) != classes.end()) {
+      return false;
+    }
+    if (classes.find(name) != classes.end()) {
+      return false;
+    }
+    return true;
+  }
+
+ public:
+  GlobalScope() { parent = nullptr; }
+};
\ No newline at end of file
diff --git a/include/semantic/visitor.h b/include/semantic/visitor.h
index 0ccfe3f..e4b2c80 100644
--- a/include/semantic/visitor.h
+++ b/include/semantic/visitor.h
@@ -4,9 +4,10 @@
 #include <stack>
 #include <vector>
 #include "MXParserVisitor.h"
+#include "ast/scope.hpp"
 #include "tools.h"
 class Visitor : public MXParserVisitor {
-  std::vector<ASTNodeType> nodetype_stk;
+  std::vector<std::pair<ASTNodeType, std::shared_ptr<ScopeBase>>> nodetype_stk;
 
  public:
   std::any visitMxprog(MXParser::MxprogContext *context) override;
diff --git a/include/tools.h b/include/tools.h
index 60ac182..e01f4a1 100644
--- a/include/tools.h
+++ b/include/tools.h
@@ -1,5 +1,6 @@
 #pragma once
 #include <stdexcept>
+#include <variant>
 enum class ASTNodeType {
   // Expression nodes
   NewArrayExpr,
@@ -58,4 +59,12 @@ class SemanticError : public std::exception {
   SemanticError(const std::string &msg, int error_code) : msg(msg), error_code(error_code) {}
   const char *what() const noexcept override { return msg.c_str(); }
   int GetErrorCode() const { return error_code; }
-};
\ No newline at end of file
+};
+
+using IdentifierType = std::string;
+struct ArrayType {
+  bool has_base_type;
+  IdentifierType basetype;
+  size_t level;
+};
+using ExprTypeInfo = std::variant<IdentifierType, ArrayType>;
\ No newline at end of file
diff --git a/src/semantic/semantic.cpp b/src/semantic/semantic.cpp
index 564aa7c..6ddcdaf 100644
--- a/src/semantic/semantic.cpp
+++ b/src/semantic/semantic.cpp
@@ -27,14 +27,16 @@ std::shared_ptr<Program_ASTNode> CheckAndDecorate(std::shared_ptr<Program_ASTNod
 void SemanticCheck(std::istream &fin, std::shared_ptr<Program_ASTNode> &ast_out) {
   antlr4::ANTLRInputStream input(fin);
   MXLexer lexer(&input);
+  MXErrorListener error_listener;
+  lexer.removeErrorListeners();
+  lexer.addErrorListener(&error_listener);
   antlr4::CommonTokenStream tokens(&lexer);
   tokens.fill();
   MXParser parser(&tokens);
   parser.removeErrorListeners();
-  MXErrorListener error_listener;
   parser.addErrorListener(&error_listener);
   antlr4::tree::ParseTree *tree = parser.mxprog();
-  if (!error_listener.IsOk()) throw SemanticError("Fatal error: syntax error", 1);
+  if (!error_listener.IsOk()) throw SemanticError("Invalid Identifier", 1);
   Visitor visitor;
   std::shared_ptr<Program_ASTNode> ast = BuildAST(&visitor, tree);
   ast_out = CheckAndDecorate(ast);
diff --git a/src/semantic/visitor.cpp b/src/semantic/visitor.cpp
index 4dc7a4f..90835d2 100644
--- a/src/semantic/visitor.cpp
+++ b/src/semantic/visitor.cpp
@@ -4,6 +4,7 @@
 #include "MXParser.h"
 #include "MXParserVisitor.h"
 #include "ast/ast.h"
+#include "ast/scope.hpp"
 #include "tools.h"
 
 std::any Visitor::visitMxprog(MXParser::MxprogContext *context) {
@@ -13,7 +14,9 @@ std::any Visitor::visitMxprog(MXParser::MxprogContext *context) {
   program->start_char_pos = context->getStart()->getCharPositionInLine();
   program->end_line = context->getStop()->getLine();
   program->end_char_pos = context->getStop()->getCharPositionInLine();
-  nodetype_stk.push_back(ASTNodeType::Program);
+  auto cur_scope = std::make_shared<GlobalScope>();
+  program->current_scope = cur_scope;
+  nodetype_stk.push_back({ASTNodeType::Program, cur_scope});
 
   for (auto def : context->children) {
     if (auto classDefContext = dynamic_cast<MXParser::Class_defContext *>(def)) {
@@ -46,7 +49,10 @@ std::any Visitor::visitFunction_def(MXParser::Function_defContext *context) {
   func->start_char_pos = context->getStart()->getCharPositionInLine();
   func->end_line = context->getStop()->getLine();
   func->end_char_pos = context->getStop()->getCharPositionInLine();
-  nodetype_stk.push_back(ASTNodeType::FuncDef);
+  auto cur_scope = std::make_shared<FunctionScope>();
+  cur_scope->parent = nodetype_stk.back().second.get();
+  func->current_scope = cur_scope;
+  nodetype_stk.push_back({ASTNodeType::FuncDef, func->current_scope});
   std::string return_type_str;
 
   if (auto type_context = dynamic_cast<MXParser::TypeContext *>(context->children[0])) {
@@ -73,6 +79,7 @@ std::any Visitor::visitFunction_def(MXParser::Function_defContext *context) {
     std::cerr << std::string(nodetype_stk.size() * 2, ' ') << "recorded return type is [array]" << return_type_str
               << " with dimensions=" << return_dimensions << std::endl;
   }
+  cur_scope->schema.return_type = func->return_type;
   func->func_name = context->children[1 + 2 * return_dimensions]->getText();
   std::cerr << std::string(nodetype_stk.size() * 2, ' ') << "func_name=" << func->func_name << std::endl;
   size_t cur = 3 + 2 * return_dimensions;
@@ -115,8 +122,19 @@ std::any Visitor::visitFunction_def(MXParser::Function_defContext *context) {
                 << std::endl;
     }
     func->params.push_back(std::make_pair(cur_para_name, cur_para_type));
+    cur_scope->schema.arguments.push_back(std::make_pair(cur_para_type, cur_para_name));
     cur++;
   }
+  if (ClassDefScope *cparent = dynamic_cast<ClassDefScope *>(cur_scope->parent)) {
+    if (!cparent->add_function(func->func_name, cur_scope)) {
+      throw SemanticError("Function name " + func->func_name + " is not available", 1);
+    }
+  } else if (GlobalScope *gparent = dynamic_cast<GlobalScope *>(cur_scope->parent)) {
+    if (!gparent->add_function(func->func_name, cur_scope)) {
+      throw SemanticError("Function name " + func->func_name + " is not available", 1);
+    }
+  } else
+    throw std::runtime_error("unknown parent scope type");
   func->func_body = std::dynamic_pointer_cast<SuiteStatement_ASTNode>(
       std::any_cast<std::shared_ptr<Statement_ASTNode>>(visit(context->suite())));
   nodetype_stk.pop_back();
@@ -129,7 +147,15 @@ std::any Visitor::visitClass_def(MXParser::Class_defContext *context) {
   class_def->start_char_pos = context->getStart()->getCharPositionInLine();
   class_def->end_line = context->getStop()->getLine();
   class_def->end_char_pos = context->getStop()->getCharPositionInLine();
-  nodetype_stk.push_back(ASTNodeType::ClassDef);
+  auto cur_scope = std::make_shared<ClassDefScope>();
+  cur_scope->parent = nodetype_stk.back().second.get();
+  class_def->current_scope = cur_scope;
+  GlobalScope *gparent = dynamic_cast<GlobalScope *>(cur_scope->parent);
+  assert(gparent != nullptr);
+  if (!gparent->add_class(context->ID()->getText(), cur_scope)) {
+    throw SemanticError("Class name " + context->ID()->getText() + " is not available", 1);
+  }
+  nodetype_stk.push_back({ASTNodeType::ClassDef, class_def->current_scope});
 
   class_def->class_name = context->ID()->getText();
   std::cerr << std::string(nodetype_stk.size() * 2, ' ') << "building a class named " << class_def->class_name
@@ -160,7 +186,8 @@ std::any Visitor::visitClass_var_def(MXParser::Class_var_defContext *context) {
   member_var_def->start_char_pos = context->getStart()->getCharPositionInLine();
   member_var_def->end_line = context->getStop()->getLine();
   member_var_def->end_char_pos = context->getStop()->getCharPositionInLine();
-  nodetype_stk.push_back(ASTNodeType::ClassVariable);
+  member_var_def->current_scope = nodetype_stk.back().second;
+  nodetype_stk.push_back({ASTNodeType::ClassVariable, member_var_def->current_scope});
 
   std::string define_type_base;
   if (auto type_context = dynamic_cast<MXParser::TypeContext *>(context->children[0])) {
@@ -190,6 +217,9 @@ std::any Visitor::visitClass_var_def(MXParser::Class_var_defContext *context) {
     member_var_def->vars.push_back(std::make_pair(id->getText(), nullptr));
     std::cerr << std::string(nodetype_stk.size() * 2, ' ') << "recorded member variable name is " << id->getText()
               << std::endl;
+    if (!member_var_def->current_scope->add_variable(id->getText(), member_var_def->var_type)) {
+      throw SemanticError("Variable name " + id->getText() + " is not available", 1);
+    }
   }
 
   nodetype_stk.pop_back();
@@ -203,7 +233,11 @@ std::any Visitor::visitClass_constructor(MXParser::Class_constructorContext *con
   construct_func->start_char_pos = context->getStart()->getCharPositionInLine();
   construct_func->end_line = context->getStop()->getLine();
   construct_func->end_char_pos = context->getStop()->getCharPositionInLine();
-  nodetype_stk.push_back(ASTNodeType::Constructor);
+  auto cur_scope = std::make_shared<FunctionScope>();
+  cur_scope->parent = nodetype_stk.back().second.get();
+  construct_func->current_scope = cur_scope;
+  cur_scope->schema.return_type = "null";
+  nodetype_stk.push_back({ASTNodeType::Constructor, construct_func->current_scope});
 
   construct_func->func_body = std::dynamic_pointer_cast<SuiteStatement_ASTNode>(
       std::any_cast<std::shared_ptr<Statement_ASTNode>>(visit(context->suite())));
@@ -219,7 +253,12 @@ std::any Visitor::visitSuite(MXParser::SuiteContext *context) {
   suite_node->start_char_pos = context->getStart()->getCharPositionInLine();
   suite_node->end_line = context->getStop()->getLine();
   suite_node->end_char_pos = context->getStop()->getCharPositionInLine();
-  nodetype_stk.push_back(ASTNodeType::SuiteStatement);
+  auto cur_scope = std::make_shared<LocalScope>();
+  cur_scope->parent = nodetype_stk.back().second.get();
+  suite_node->current_scope = cur_scope;
+  assert(nodetype_stk.size() > 0);
+  cur_scope->parent = nodetype_stk.back().second.get();
+  nodetype_stk.push_back({ASTNodeType::SuiteStatement, cur_scope});
   std::cerr << std::string(nodetype_stk.size() * 2, ' ') << "Adding suite statements" << std::endl;
 
   std::vector<MXParser::StatementContext *> stmts = context->statement();
@@ -250,7 +289,9 @@ std::any Visitor::visitExpr_statement(MXParser::Expr_statementContext *context)
   expr_stmt->start_char_pos = context->getStart()->getCharPositionInLine();
   expr_stmt->end_line = context->getStop()->getLine();
   expr_stmt->end_char_pos = context->getStop()->getCharPositionInLine();
-  nodetype_stk.push_back(ASTNodeType::ExprStatement);
+  assert(nodetype_stk.size() > 0);
+  expr_stmt->current_scope = nodetype_stk.back().second;
+  nodetype_stk.push_back({ASTNodeType::ExprStatement, expr_stmt->current_scope});
   std::cerr << std::string(nodetype_stk.size() * 2, ' ') << "Adding an expression statement" << std::endl;
   expr_stmt->expr = std::any_cast<std::shared_ptr<Expr_ASTNode>>(visit(context->expr()));
   nodetype_stk.pop_back();
@@ -263,7 +304,9 @@ std::any Visitor::visitIf_statement(MXParser::If_statementContext *context) {
   if_stmt->start_char_pos = context->getStart()->getCharPositionInLine();
   if_stmt->end_line = context->getStop()->getLine();
   if_stmt->end_char_pos = context->getStop()->getCharPositionInLine();
-  nodetype_stk.push_back(ASTNodeType::IfStatement);
+  assert(nodetype_stk.size() > 0);
+  if_stmt->current_scope = nodetype_stk.back().second;
+  nodetype_stk.push_back({ASTNodeType::IfStatement, if_stmt->current_scope});
   std::cerr << std::string(nodetype_stk.size() * 2, ' ') << "Adding an if statement" << std::endl;
   if_stmt->condition = std::any_cast<std::shared_ptr<Expr_ASTNode>>(visit(context->expr()));
   std::vector<MXParser::StatementContext *> sub_stmts = context->statement();
@@ -285,7 +328,9 @@ std::any Visitor::visitWhile_statement(MXParser::While_statementContext *context
   while_stmt->start_char_pos = context->getStart()->getCharPositionInLine();
   while_stmt->end_line = context->getStop()->getLine();
   while_stmt->end_char_pos = context->getStop()->getCharPositionInLine();
-  nodetype_stk.push_back(ASTNodeType::WhileStatement);
+  assert(nodetype_stk.size() > 0);
+  while_stmt->current_scope = nodetype_stk.back().second;
+  nodetype_stk.push_back({ASTNodeType::WhileStatement, while_stmt->current_scope});
   std::cerr << std::string(nodetype_stk.size() * 2, ' ') << "Adding a while statement" << std::endl;
   while_stmt->condition = std::any_cast<std::shared_ptr<Expr_ASTNode>>(visit(context->expr()));
   while_stmt->loop_body = std::any_cast<std::shared_ptr<Statement_ASTNode>>(visit(context->statement()));
@@ -299,7 +344,10 @@ std::any Visitor::visitFor_statement(MXParser::For_statementContext *context) {
   for_stmt->start_char_pos = context->getStart()->getCharPositionInLine();
   for_stmt->end_line = context->getStop()->getLine();
   for_stmt->end_char_pos = context->getStop()->getCharPositionInLine();
-  nodetype_stk.push_back(ASTNodeType::ForStatement);
+  auto cur_scope = std::make_shared<LocalScope>();
+  cur_scope->parent = nodetype_stk.back().second.get();
+  for_stmt->current_scope = cur_scope;
+  nodetype_stk.push_back({ASTNodeType::ForStatement, for_stmt->current_scope});
   std::cerr << std::string(nodetype_stk.size() * 2, ' ') << "Adding a for statement" << std::endl;
   size_t cur = 2;
   if (dynamic_cast<antlr4::tree::TerminalNode *>(context->children[cur]) != nullptr &&
@@ -371,7 +419,9 @@ std::any Visitor::visitJmp_statement(MXParser::Jmp_statementContext *context) {
   jmp_stmt->start_char_pos = context->getStart()->getCharPositionInLine();
   jmp_stmt->end_line = context->getStop()->getLine();
   jmp_stmt->end_char_pos = context->getStop()->getCharPositionInLine();
-  nodetype_stk.push_back(ASTNodeType::JmpStatement);
+  assert(nodetype_stk.size() > 0);
+  jmp_stmt->current_scope = nodetype_stk.back().second;
+  nodetype_stk.push_back({ASTNodeType::JmpStatement, jmp_stmt->current_scope});
   std::cerr << std::string(nodetype_stk.size() * 2, ' ') << "Adding a jmp statement" << std::endl;
   if (context->RETURN() != nullptr) {
     jmp_stmt->jmp_type = 0;
@@ -401,7 +451,9 @@ std::any Visitor::visitDefine_statement(MXParser::Define_statementContext *conte
   def_stmt->start_char_pos = context->getStart()->getCharPositionInLine();
   def_stmt->end_line = context->getStop()->getLine();
   def_stmt->end_char_pos = context->getStop()->getCharPositionInLine();
-  nodetype_stk.push_back(ASTNodeType::DefinitionStatement);
+  assert(nodetype_stk.size() > 0);
+  def_stmt->current_scope = nodetype_stk.back().second;
+  nodetype_stk.push_back({ASTNodeType::DefinitionStatement, def_stmt->current_scope});
   std::cerr << std::string(nodetype_stk.size() * 2, ' ') << "Adding a definition statement" << std::endl;
   std::string define_type_base;
   if (auto type_context = dynamic_cast<MXParser::TypeContext *>(context->children[0])) {
@@ -436,6 +488,8 @@ std::any Visitor::visitDefine_statement(MXParser::Define_statementContext *conte
     if (dynamic_cast<antlr4::tree::TerminalNode *>(context->children[i]) != nullptr &&
         dynamic_cast<antlr4::tree::TerminalNode *>(context->children[i])->getSymbol()->getType() == MXParser::ID) {
       def_stmt->vars.push_back(std::make_pair(context->children[i]->getText(), nullptr));
+      if (!def_stmt->current_scope->add_variable(context->children[i]->getText(), def_stmt->var_type))
+        throw SemanticError("Variable " + context->children[i]->getText() + " already defined", 1);
     } else
       throw std::runtime_error("unknown subnode occurred in visitDefine_statement");
     i++;
@@ -456,7 +510,9 @@ std::any Visitor::visitGgll_expression(MXParser::Ggll_expressionContext *context
   ggll_expr->start_char_pos = context->getStart()->getCharPositionInLine();
   ggll_expr->end_line = context->getStop()->getLine();
   ggll_expr->end_char_pos = context->getStop()->getCharPositionInLine();
-  nodetype_stk.push_back(ASTNodeType::GGLLExpr);
+  assert(nodetype_stk.size() > 0);
+  ggll_expr->current_scope = nodetype_stk.back().second;
+  nodetype_stk.push_back({ASTNodeType::GGLLExpr, ggll_expr->current_scope});
   ggll_expr->op = context->children[1]->getText();
   ggll_expr->left = std::any_cast<std::shared_ptr<Expr_ASTNode>>(visit(context->children[0]));
   ggll_expr->right = std::any_cast<std::shared_ptr<Expr_ASTNode>>(visit(context->children[2]));
@@ -470,7 +526,8 @@ std::any Visitor::visitBxor_expression(MXParser::Bxor_expressionContext *context
   bxor_expr->start_char_pos = context->getStart()->getCharPositionInLine();
   bxor_expr->end_line = context->getStop()->getLine();
   bxor_expr->end_char_pos = context->getStop()->getCharPositionInLine();
-  nodetype_stk.push_back(ASTNodeType::BXorExpr);
+  bxor_expr->current_scope = nodetype_stk.back().second;
+  nodetype_stk.push_back({ASTNodeType::BXorExpr, bxor_expr->current_scope});
   bxor_expr->op = context->children[1]->getText();
   bxor_expr->left = std::any_cast<std::shared_ptr<Expr_ASTNode>>(visit(context->children[0]));
   bxor_expr->right = std::any_cast<std::shared_ptr<Expr_ASTNode>>(visit(context->children[2]));
@@ -484,7 +541,8 @@ std::any Visitor::visitSuffix_expression(MXParser::Suffix_expressionContext *con
   suffix_expr->start_char_pos = context->getStart()->getCharPositionInLine();
   suffix_expr->end_line = context->getStop()->getLine();
   suffix_expr->end_char_pos = context->getStop()->getCharPositionInLine();
-  nodetype_stk.push_back(ASTNodeType::SuffixExpr);
+  suffix_expr->current_scope = nodetype_stk.back().second;
+  nodetype_stk.push_back({ASTNodeType::SuffixExpr, suffix_expr->current_scope});
   suffix_expr->op = context->children[1]->getText();
   suffix_expr->base = std::any_cast<std::shared_ptr<Expr_ASTNode>>(visit(context->expr()));
   nodetype_stk.pop_back();
@@ -497,7 +555,8 @@ std::any Visitor::visitLand_expression(MXParser::Land_expressionContext *context
   land_expr->start_char_pos = context->getStart()->getCharPositionInLine();
   land_expr->end_line = context->getStop()->getLine();
   land_expr->end_char_pos = context->getStop()->getCharPositionInLine();
-  nodetype_stk.push_back(ASTNodeType::LAndExpr);
+  land_expr->current_scope = nodetype_stk.back().second;
+  nodetype_stk.push_back({ASTNodeType::LAndExpr, land_expr->current_scope});
   land_expr->op = context->children[1]->getText();
   land_expr->left = std::any_cast<std::shared_ptr<Expr_ASTNode>>(visit(context->children[0]));
   land_expr->right = std::any_cast<std::shared_ptr<Expr_ASTNode>>(visit(context->children[2]));
@@ -511,7 +570,8 @@ std::any Visitor::visitPm_expression(MXParser::Pm_expressionContext *context) {
   pm_expr->start_char_pos = context->getStart()->getCharPositionInLine();
   pm_expr->end_line = context->getStop()->getLine();
   pm_expr->end_char_pos = context->getStop()->getCharPositionInLine();
-  nodetype_stk.push_back(ASTNodeType::PMExpr);
+  pm_expr->current_scope = nodetype_stk.back().second;
+  nodetype_stk.push_back({ASTNodeType::PMExpr, pm_expr->current_scope});
   pm_expr->op = context->children[1]->getText();
   pm_expr->left = std::any_cast<std::shared_ptr<Expr_ASTNode>>(visit(context->children[0]));
   pm_expr->right = std::any_cast<std::shared_ptr<Expr_ASTNode>>(visit(context->children[2]));
@@ -525,7 +585,8 @@ std::any Visitor::visitIndex_expression(MXParser::Index_expressionContext *conte
   idx_expr->start_char_pos = context->getStart()->getCharPositionInLine();
   idx_expr->end_line = context->getStop()->getLine();
   idx_expr->end_char_pos = context->getStop()->getCharPositionInLine();
-  nodetype_stk.push_back(ASTNodeType::IndexExpr);
+  idx_expr->current_scope = nodetype_stk.back().second;
+  nodetype_stk.push_back({ASTNodeType::IndexExpr, idx_expr->current_scope});
   auto sub_exprs = context->expr();
   idx_expr->base = std::any_cast<std::shared_ptr<Expr_ASTNode>>(visit(sub_exprs[0]));
   for (size_t i = 1; i < sub_exprs.size(); i++) {
@@ -541,7 +602,8 @@ std::any Visitor::visitOpposite_expression(MXParser::Opposite_expressionContext
   oppsite_expr->start_char_pos = context->getStart()->getCharPositionInLine();
   oppsite_expr->end_line = context->getStop()->getLine();
   oppsite_expr->end_char_pos = context->getStop()->getCharPositionInLine();
-  nodetype_stk.push_back(ASTNodeType::OppositeExpr);
+  oppsite_expr->current_scope = nodetype_stk.back().second;
+  nodetype_stk.push_back({ASTNodeType::OppositeExpr, oppsite_expr->current_scope});
   oppsite_expr->base = std::any_cast<std::shared_ptr<Expr_ASTNode>>(visit(context->expr()));
   nodetype_stk.pop_back();
   return std::static_pointer_cast<Expr_ASTNode>(oppsite_expr);
@@ -553,7 +615,8 @@ std::any Visitor::visitNew_array_expression(MXParser::New_array_expressionContex
   new_array->start_char_pos = context->getStart()->getCharPositionInLine();
   new_array->end_line = context->getStop()->getLine();
   new_array->end_char_pos = context->getStop()->getCharPositionInLine();
-  nodetype_stk.push_back(ASTNodeType::NewArrayExpr);
+  new_array->current_scope = nodetype_stk.back().second;
+  nodetype_stk.push_back({ASTNodeType::NewArrayExpr, new_array->current_scope});
 
   std::cerr << std::string(nodetype_stk.size() * 2, ' ') << "Adding a new array expression" << std::endl;
   size_t total_dimensions = context->LBRACKET().size();
@@ -596,7 +659,8 @@ std::any Visitor::visitAccess_expression(MXParser::Access_expressionContext *con
     access_expr->type = ASTNodeType::MemberFunctionAccessExpr;
     access_expr->is_function = true;
   }
-  nodetype_stk.push_back(access_expr->type);
+  access_expr->current_scope = nodetype_stk.back().second;
+  nodetype_stk.push_back({access_expr->type, access_expr->current_scope});
   auto sub_exprs = context->expr();
   access_expr->base = std::any_cast<std::shared_ptr<Expr_ASTNode>>(visit(sub_exprs[0]));
   access_expr->member = context->ID()->getText();
@@ -613,7 +677,8 @@ std::any Visitor::visitBand_expression(MXParser::Band_expressionContext *context
   band_expr->start_char_pos = context->getStart()->getCharPositionInLine();
   band_expr->end_line = context->getStop()->getLine();
   band_expr->end_char_pos = context->getStop()->getCharPositionInLine();
-  nodetype_stk.push_back(ASTNodeType::BAndExpr);
+  band_expr->current_scope = nodetype_stk.back().second;
+  nodetype_stk.push_back({ASTNodeType::BAndExpr, band_expr->current_scope});
   band_expr->op = context->children[1]->getText();
   band_expr->left = std::any_cast<std::shared_ptr<Expr_ASTNode>>(visit(context->children[0]));
   band_expr->right = std::any_cast<std::shared_ptr<Expr_ASTNode>>(visit(context->children[2]));
@@ -627,7 +692,8 @@ std::any Visitor::visitNew_construct_expression(MXParser::New_construct_expressi
   new_construct_expr->start_char_pos = context->getStart()->getCharPositionInLine();
   new_construct_expr->end_line = context->getStop()->getLine();
   new_construct_expr->end_char_pos = context->getStop()->getCharPositionInLine();
-  nodetype_stk.push_back(ASTNodeType::NewConstructExpr);
+  new_construct_expr->current_scope = nodetype_stk.back().second;
+  nodetype_stk.push_back({ASTNodeType::NewConstructExpr, new_construct_expr->current_scope});
   new_construct_expr->expr_type_info = context->type()->getText();
   nodetype_stk.pop_back();
   return std::static_pointer_cast<Expr_ASTNode>(new_construct_expr);
@@ -639,7 +705,8 @@ std::any Visitor::visitTernary_expression(MXParser::Ternary_expressionContext *c
   ternary_expr->start_char_pos = context->getStart()->getCharPositionInLine();
   ternary_expr->end_line = context->getStop()->getLine();
   ternary_expr->end_char_pos = context->getStop()->getCharPositionInLine();
-  nodetype_stk.push_back(ASTNodeType::TernaryExpr);
+  ternary_expr->current_scope = nodetype_stk.back().second;
+  nodetype_stk.push_back({ASTNodeType::TernaryExpr, ternary_expr->current_scope});
   auto expr_subnodes = context->expr();
   ternary_expr->condition = std::any_cast<std::shared_ptr<Expr_ASTNode>>(visit(expr_subnodes[0]));
   ternary_expr->src1 = std::any_cast<std::shared_ptr<Expr_ASTNode>>(visit(expr_subnodes[1]));
@@ -654,7 +721,8 @@ std::any Visitor::visitBnot_expression(MXParser::Bnot_expressionContext *context
   bnot_expr->start_char_pos = context->getStart()->getCharPositionInLine();
   bnot_expr->end_line = context->getStop()->getLine();
   bnot_expr->end_char_pos = context->getStop()->getCharPositionInLine();
-  nodetype_stk.push_back(ASTNodeType::BNotExpr);
+  bnot_expr->current_scope = nodetype_stk.back().second;
+  nodetype_stk.push_back({ASTNodeType::BNotExpr, bnot_expr->current_scope});
   bnot_expr->base = std::any_cast<std::shared_ptr<Expr_ASTNode>>(visit(context->expr()));
   nodetype_stk.pop_back();
   return std::static_pointer_cast<Expr_ASTNode>(bnot_expr);
@@ -666,7 +734,8 @@ std::any Visitor::visitLnot_expression(MXParser::Lnot_expressionContext *context
   lnot_expr->start_char_pos = context->getStart()->getCharPositionInLine();
   lnot_expr->end_line = context->getStop()->getLine();
   lnot_expr->end_char_pos = context->getStop()->getCharPositionInLine();
-  nodetype_stk.push_back(ASTNodeType::LNotExpr);
+  lnot_expr->current_scope = nodetype_stk.back().second;
+  nodetype_stk.push_back({ASTNodeType::LNotExpr, lnot_expr->current_scope});
   lnot_expr->base = std::any_cast<std::shared_ptr<Expr_ASTNode>>(visit(context->expr()));
   nodetype_stk.pop_back();
   return std::static_pointer_cast<Expr_ASTNode>(lnot_expr);
@@ -678,7 +747,8 @@ std::any Visitor::visitPrefix_expression(MXParser::Prefix_expressionContext *con
   prefix_expr->start_char_pos = context->getStart()->getCharPositionInLine();
   prefix_expr->end_line = context->getStop()->getLine();
   prefix_expr->end_char_pos = context->getStop()->getCharPositionInLine();
-  nodetype_stk.push_back(ASTNodeType::PrefixExpr);
+  prefix_expr->current_scope = nodetype_stk.back().second;
+  nodetype_stk.push_back({ASTNodeType::PrefixExpr, prefix_expr->current_scope});
   prefix_expr->op = context->children[0]->getText();
   prefix_expr->base = std::any_cast<std::shared_ptr<Expr_ASTNode>>(visit(context->expr()));
   nodetype_stk.pop_back();
@@ -691,7 +761,8 @@ std::any Visitor::visitRl_expression(MXParser::Rl_expressionContext *context) {
   rl_expr->start_char_pos = context->getStart()->getCharPositionInLine();
   rl_expr->end_line = context->getStop()->getLine();
   rl_expr->end_char_pos = context->getStop()->getCharPositionInLine();
-  nodetype_stk.push_back(ASTNodeType::RLExpr);
+  rl_expr->current_scope = nodetype_stk.back().second;
+  nodetype_stk.push_back({ASTNodeType::RLExpr, rl_expr->current_scope});
   rl_expr->op = context->children[1]->getText();
   rl_expr->left = std::any_cast<std::shared_ptr<Expr_ASTNode>>(visit(context->children[0]));
   rl_expr->right = std::any_cast<std::shared_ptr<Expr_ASTNode>>(visit(context->children[2]));
@@ -705,7 +776,8 @@ std::any Visitor::visitAssign_expression(MXParser::Assign_expressionContext *con
   assign_expr->start_char_pos = context->getStart()->getCharPositionInLine();
   assign_expr->end_line = context->getStop()->getLine();
   assign_expr->end_char_pos = context->getStop()->getCharPositionInLine();
-  nodetype_stk.push_back(ASTNodeType::AssignExpr);
+  assign_expr->current_scope = nodetype_stk.back().second;
+  nodetype_stk.push_back({ASTNodeType::AssignExpr, assign_expr->current_scope});
   assign_expr->dest = std::any_cast<std::shared_ptr<Expr_ASTNode>>(visit(context->expr(0)));
   assign_expr->src = std::any_cast<std::shared_ptr<Expr_ASTNode>>(visit(context->expr(1)));
   nodetype_stk.pop_back();
@@ -718,7 +790,8 @@ std::any Visitor::visitMdm_expression(MXParser::Mdm_expressionContext *context)
   mdm_expr->start_char_pos = context->getStart()->getCharPositionInLine();
   mdm_expr->end_line = context->getStop()->getLine();
   mdm_expr->end_char_pos = context->getStop()->getCharPositionInLine();
-  nodetype_stk.push_back(ASTNodeType::MDMExpr);
+  mdm_expr->current_scope = nodetype_stk.back().second;
+  nodetype_stk.push_back({ASTNodeType::MDMExpr, mdm_expr->current_scope});
   mdm_expr->op = context->children[1]->getText();
   mdm_expr->left = std::any_cast<std::shared_ptr<Expr_ASTNode>>(visit(context->children[0]));
   mdm_expr->right = std::any_cast<std::shared_ptr<Expr_ASTNode>>(visit(context->children[2]));
@@ -732,7 +805,8 @@ std::any Visitor::visitNew_expression(MXParser::New_expressionContext *context)
   new_expr->start_char_pos = context->getStart()->getCharPositionInLine();
   new_expr->end_line = context->getStop()->getLine();
   new_expr->end_char_pos = context->getStop()->getCharPositionInLine();
-  nodetype_stk.push_back(ASTNodeType::NewExpr);
+  new_expr->current_scope = nodetype_stk.back().second;
+  nodetype_stk.push_back({ASTNodeType::NewExpr, new_expr->current_scope});
   new_expr->expr_type_info = context->type()->getText();
   nodetype_stk.pop_back();
   return std::static_pointer_cast<Expr_ASTNode>(new_expr);
@@ -744,7 +818,8 @@ std::any Visitor::visitNe_expression(MXParser::Ne_expressionContext *context) {
   ne_expr->start_char_pos = context->getStart()->getCharPositionInLine();
   ne_expr->end_line = context->getStop()->getLine();
   ne_expr->end_char_pos = context->getStop()->getCharPositionInLine();
-  nodetype_stk.push_back(ASTNodeType::NEExpr);
+  ne_expr->current_scope = nodetype_stk.back().second;
+  nodetype_stk.push_back({ASTNodeType::NEExpr, ne_expr->current_scope});
   ne_expr->op = context->children[1]->getText();
   ne_expr->left = std::any_cast<std::shared_ptr<Expr_ASTNode>>(visit(context->children[0]));
   ne_expr->right = std::any_cast<std::shared_ptr<Expr_ASTNode>>(visit(context->children[2]));
@@ -758,7 +833,8 @@ std::any Visitor::visitBor_expression(MXParser::Bor_expressionContext *context)
   bor_expr->start_char_pos = context->getStart()->getCharPositionInLine();
   bor_expr->end_line = context->getStop()->getLine();
   bor_expr->end_char_pos = context->getStop()->getCharPositionInLine();
-  nodetype_stk.push_back(ASTNodeType::BOrExpr);
+  bor_expr->current_scope = nodetype_stk.back().second;
+  nodetype_stk.push_back({ASTNodeType::BOrExpr, bor_expr->current_scope});
   bor_expr->op = context->children[1]->getText();
   bor_expr->left = std::any_cast<std::shared_ptr<Expr_ASTNode>>(visit(context->children[0]));
   bor_expr->right = std::any_cast<std::shared_ptr<Expr_ASTNode>>(visit(context->children[2]));
@@ -772,7 +848,8 @@ std::any Visitor::visitLor_expression(MXParser::Lor_expressionContext *context)
   lor_expr->start_char_pos = context->getStart()->getCharPositionInLine();
   lor_expr->end_line = context->getStop()->getLine();
   lor_expr->end_char_pos = context->getStop()->getCharPositionInLine();
-  nodetype_stk.push_back(ASTNodeType::LOrExpr);
+  lor_expr->current_scope = nodetype_stk.back().second;
+  nodetype_stk.push_back({ASTNodeType::LOrExpr, lor_expr->current_scope});
   lor_expr->op = context->children[1]->getText();
   lor_expr->left = std::any_cast<std::shared_ptr<Expr_ASTNode>>(visit(context->children[0]));
   lor_expr->right = std::any_cast<std::shared_ptr<Expr_ASTNode>>(visit(context->children[2]));
@@ -786,7 +863,8 @@ std::any Visitor::visitThis_expr(MXParser::This_exprContext *context) {
   this_expr->start_char_pos = context->getStart()->getCharPositionInLine();
   this_expr->end_line = context->getStop()->getLine();
   this_expr->end_char_pos = context->getStop()->getCharPositionInLine();
-  nodetype_stk.push_back(ASTNodeType::ThisExpr);
+  this_expr->current_scope = nodetype_stk.back().second;
+  nodetype_stk.push_back({ASTNodeType::ThisExpr, this_expr->current_scope});
   nodetype_stk.pop_back();
   return std::static_pointer_cast<Expr_ASTNode>(this_expr);
 }
@@ -797,7 +875,8 @@ std::any Visitor::visitParen_expr(MXParser::Paren_exprContext *context) {
   paren_expr->start_char_pos = context->getStart()->getCharPositionInLine();
   paren_expr->end_line = context->getStop()->getLine();
   paren_expr->end_char_pos = context->getStop()->getCharPositionInLine();
-  nodetype_stk.push_back(ASTNodeType::ParenExpr);
+  paren_expr->current_scope = nodetype_stk.back().second;
+  nodetype_stk.push_back({ASTNodeType::ParenExpr, paren_expr->current_scope});
   paren_expr->expr = std::any_cast<std::shared_ptr<Expr_ASTNode>>(visit(context->expr()));
   nodetype_stk.pop_back();
   return std::static_pointer_cast<Expr_ASTNode>(paren_expr);
@@ -809,7 +888,8 @@ std::any Visitor::visitId_expr(MXParser::Id_exprContext *context) {
   id_expr->start_char_pos = context->getStart()->getCharPositionInLine();
   id_expr->end_line = context->getStop()->getLine();
   id_expr->end_char_pos = context->getStop()->getCharPositionInLine();
-  nodetype_stk.push_back(ASTNodeType::IDExpr);
+  id_expr->current_scope = nodetype_stk.back().second;
+  nodetype_stk.push_back({ASTNodeType::IDExpr, id_expr->current_scope});
   id_expr->id = IdentifierType{context->ID()->getText()};
   nodetype_stk.pop_back();
   return std::static_pointer_cast<Expr_ASTNode>(id_expr);
@@ -821,7 +901,8 @@ std::any Visitor::visitFunction_call_expr(MXParser::Function_call_exprContext *c
   func_call_expr->start_char_pos = context->getStart()->getCharPositionInLine();
   func_call_expr->end_line = context->getStop()->getLine();
   func_call_expr->end_char_pos = context->getStop()->getCharPositionInLine();
-  nodetype_stk.push_back(ASTNodeType::FunctionCallExpr);
+  func_call_expr->current_scope = nodetype_stk.back().second;
+  nodetype_stk.push_back({ASTNodeType::FunctionCallExpr, func_call_expr->current_scope});
   func_call_expr->func_name = IdentifierType{context->ID()->getText()};
   auto expr_subnodes = context->expr();
   for (auto expr_subnode : expr_subnodes) {
@@ -841,7 +922,8 @@ std::any Visitor::visitFormatted_string(MXParser::Formatted_stringContext *conte
   fmt_expr->start_char_pos = context->getStart()->getCharPositionInLine();
   fmt_expr->end_line = context->getStop()->getLine();
   fmt_expr->end_char_pos = context->getStop()->getCharPositionInLine();
-  nodetype_stk.push_back(ASTNodeType::FormattedStringExpr);
+  fmt_expr->current_scope = nodetype_stk.back().second;
+  nodetype_stk.push_back({ASTNodeType::FormattedStringExpr, fmt_expr->current_scope});
 
   if (context->FORMAT_STRING_WHOLE() != nullptr) {
     fmt_expr->literals.push_back(context->FORMAT_STRING_WHOLE()->getText());
@@ -868,7 +950,8 @@ std::any Visitor::visitConstant(MXParser::ConstantContext *context) {
   constant_expr->start_char_pos = context->getStart()->getCharPositionInLine();
   constant_expr->end_line = context->getStop()->getLine();
   constant_expr->end_char_pos = context->getStop()->getCharPositionInLine();
-  nodetype_stk.push_back(ASTNodeType::ConstantExpr);
+  constant_expr->current_scope = nodetype_stk.back().second;
+  nodetype_stk.push_back({ASTNodeType::ConstantExpr, constant_expr->current_scope});
 
   if (context->TRUE() != nullptr || context->FALSE() != nullptr) {
     constant_expr->expr_type_info = "bool";