diff --git a/CMakeLists.txt b/CMakeLists.txt
index fe44a89..a5576f1 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -2,5 +2,5 @@ cmake_minimum_required(VERSION 3.0)
 project(lily)
 
 set(CMAKE_CXX_STANDARD 14)
-add_executable(lily src/main.cpp src/parser.cpp src/parser.c)
+add_executable(lily src/main.cpp src/parser.cpp src/parser.c src/type.cpp src/type_manager.cpp)
 target_include_directories(lily PUBLIC src)
diff --git a/src/data.hpp b/src/data.hpp
deleted file mode 100644
index dc049b5..0000000
--- a/src/data.hpp
+++ /dev/null
@@ -1,12 +0,0 @@
-#pragma once
-#include <string>
-#include <vector>
-#include "type.hpp"
-
-namespace lily {
-    struct constructor {
-        int parent_type;
-        int tag;
-        std::vector<std::weak_ptr<type>> params;
-    };
-}
diff --git a/src/parser.cpp b/src/parser.cpp
index 97bbfe9..c34d4e6 100644
--- a/src/parser.cpp
+++ b/src/parser.cpp
@@ -161,35 +161,30 @@ namespace lily {
         }
     }
 
-    static type_ptr type_tree(program& prog, pgs_tree* type, const char* source) {
+    static type* type_tree(program& prog, pgs_tree* type, const char* source) {
         std::string str = tree_str(PGS_TREE_NT_CHILD(*type, 0), source);
-        if(!prog.types.count(str)) throw error("unknown type");
-
-        return prog.types[str];
+        return prog.type_mgr.require_type(str);
     }
 
-    static void collect_type_params(program& prog, std::vector<std::weak_ptr<type>>& into, pgs_tree* params, const char* source) {
+    static void collect_type_params(program& prog, std::vector<type*>& into, pgs_tree* params, const char* source) {
         while(true) {
             pgs_tree* param = PGS_TREE_NT_CHILD(*params, 0);
-            into.push_back(std::weak_ptr<type>(type_tree(prog, param, source)));
+            into.push_back(type_tree(prog, param, source));
 
             if(PGS_TREE_NT_COUNT(*params) == 1) break;
             params = PGS_TREE_NT_CHILD(*params, 2);
         }
     }
 
-    static void collect_constructors(program& prog, int parent, pgs_tree* def, const char* source) {
+    static void collect_constructors(program& prog, type_data* parent, pgs_tree* def, const char* source) {
         int id = 0;
         while(true) {
-            constructor cons;
-            cons.tag = id++;
-            cons.parent_type = parent;
-
             pgs_tree* elem = PGS_TREE_NT_CHILD(*def, 0);
+            std::vector<type*> params;
             std::string name = tree_str(PGS_TREE_NT_CHILD(*elem, 0), source);
             if(PGS_TREE_NT_COUNT(*elem) > 1)
-                collect_type_params(prog, cons.params, PGS_TREE_NT_CHILD(*elem, 2), source);
-            prog.constructors[name] = std::move(cons);
+                collect_type_params(prog, params, PGS_TREE_NT_CHILD(*elem, 2), source);
+            parent->create_constructor(name, std::move(params));
 
             if(PGS_TREE_NT_COUNT(*def) == 1) break;
             def = PGS_TREE_NT_CHILD(*def, 2);
@@ -211,10 +206,7 @@ namespace lily {
             prog.functions[function_name] = std::move(new_function);
         } else {
             std::string data_name = tree_str(PGS_TREE_NT_CHILD(*def, 1), source);
-            if(prog.types.count(data_name)) throw error("cannot redefine type");
-
-            int new_type = prog.next_free_type_id++;
-            prog.types[data_name] = type_ptr(new type_int(new_type));
+            type_data* new_type = prog.type_mgr.create_data_type(data_name);
             collect_constructors(prog, new_type,
                     PGS_TREE_NT_CHILD(*PGS_TREE_NT_CHILD(*def, PGS_TREE_NT_COUNT(*def) - 1), 1), source);
         }
@@ -235,31 +227,6 @@ namespace lily {
         return prog;
     }
 
-    static void dump_program(program& prog) {
-        std::cout << "Constructors:" << std::endl;
-        for(auto& pair : prog.constructors) {
-            std::cout << "  " << pair.first << std::endl;
-        }
-        std::cout << std::endl;
-
-        std::cout << "Types:" << std::endl;
-        for(auto& pair : prog.types) {
-            std::cout << "  " << pair.first << std::endl;
-        }
-        std::cout << std::endl;
-
-        std::cout << "Functions:" << std::endl;
-        for(auto& pair : prog.functions) {
-            function& f = pair.second;
-            std::cout << "  " << pair.first;
-            for(auto& param : f.params) {
-                std::cout << " " << param;
-            }
-            std::cout << std::endl;
-        }
-        std::cout << std::endl;
-    }
-
     program_ptr parse(std::string s) {
         pgs_state state;
         pgs_tree* into;
@@ -271,14 +238,7 @@ namespace lily {
         }
         
         program_ptr prog = build_program(into, s.c_str());
-        dump_program(*prog);
         pgs_free_tree(into);
         return prog;
     }
-
-    program::program() {
-        types["Int"] = type_ptr(new type_int(type_id_int));
-        types["String"] = type_ptr(new type_int(type_id_str));
-        next_free_type_id = type_id_last;
-    }
 }
diff --git a/src/parser.hpp b/src/parser.hpp
index f979840..efbc2ea 100644
--- a/src/parser.hpp
+++ b/src/parser.hpp
@@ -5,16 +5,12 @@
 #include "ast.hpp"
 #include "function.hpp"
 #include "type.hpp"
-#include "data.hpp"
+#include "type_manager.hpp"
 
 namespace lily {
     struct program {
-        int next_free_type_id;
-        std::map<std::string, type_ptr> types;
-        std::map<std::string, constructor> constructors;
+        type_manager type_mgr;
         std::map<std::string, function> functions;
-
-        program();
     };
 
     typedef std::unique_ptr<program> program_ptr;
diff --git a/src/type.cpp b/src/type.cpp
new file mode 100644
index 0000000..0925c25
--- /dev/null
+++ b/src/type.cpp
@@ -0,0 +1,15 @@
+#include "type.hpp"
+
+namespace lily {
+    type_data::constructor* type_data::create_constructor(const std::string& name,
+            std::vector<type*>&& params) {
+        auto new_constructor = std::make_unique<constructor>();
+        new_constructor->id = constructors.size();
+        new_constructor->parent = this;
+        new_constructor->params = std::move(params);
+
+        constructor* raw_ptr = new_constructor.get();
+        constructors.push_back(std::move(new_constructor));
+        return raw_ptr;
+    }
+}
diff --git a/src/type.hpp b/src/type.hpp
index f71ea5c..acef15a 100644
--- a/src/type.hpp
+++ b/src/type.hpp
@@ -13,20 +13,32 @@ namespace lily {
         virtual ~type() = default;
     };
 
-    typedef std::shared_ptr<type> type_ptr;
-
-    struct type_int : type {
+    struct type_internal : type {
         int type_id;
 
-        type_int(int id) : type_id(id) {}
+        type_internal(int id) : type_id(id) {}
+    };
+
+    struct type_data : type {
+        struct constructor {
+            type_data* parent;
+            int id;
+            std::vector<type*> params;
+        };
+
+        int type_id;
+        std::vector<std::unique_ptr<constructor>> constructors;
+
+        type_data(int id) : type_id(id) {}
+        constructor* create_constructor(const std::string& name, std::vector<type*>&& params);
     };
 
     struct type_func : type {
-        type_ptr left;
-        type_ptr right;
+        type* left;
+        type* right;
 
-        type_func(type_ptr l, type_ptr r) :
-            left(std::move(l)), right(std::move(r)) {}
+        type_func(type* l, type* r) :
+            left(l), right(r) {}
     };
 }
 
diff --git a/src/type_manager.cpp b/src/type_manager.cpp
new file mode 100644
index 0000000..e495f8e
--- /dev/null
+++ b/src/type_manager.cpp
@@ -0,0 +1,41 @@
+#include "type_manager.hpp"
+#include <memory>
+#include "error.hpp"
+
+namespace lily {
+    type_manager::type_manager() {
+        create_int_type();
+        create_str_type();
+    }
+
+    type_internal* type_manager::create_int_type() {
+        auto new_type = std::make_unique<type_internal>(next_id++);
+        type_internal* raw_ptr = new_type.get();
+        types.push_back(std::move(new_type));
+        type_names["Int"] = raw_ptr;
+        return raw_ptr;
+    }
+
+    type_internal* type_manager::create_str_type() {
+        auto new_type = std::make_unique<type_internal>(next_id++);
+        type_internal* raw_ptr = new_type.get();
+        types.push_back(std::move(new_type));
+        type_names["Str"] = raw_ptr;
+        return raw_ptr;
+    }
+
+    type_data* type_manager::create_data_type(const std::string& name) {
+        if(type_names.count(name)) throw error("redefinition of type");
+
+        auto new_type = std::make_unique<type_data>(next_id++);
+        type_data* raw_ptr = new_type.get();
+        types.push_back(std::move(new_type));
+        type_names[name] = raw_ptr;
+        return raw_ptr;
+    }
+
+    type* type_manager::require_type(const std::string& name) {
+        if(!type_names.count(name)) throw error("invalid type name");
+        return type_names[name];
+    }
+}
diff --git a/src/type_manager.hpp b/src/type_manager.hpp
new file mode 100644
index 0000000..5b45984
--- /dev/null
+++ b/src/type_manager.hpp
@@ -0,0 +1,22 @@
+#pragma once
+#include <memory>
+#include <map>
+#include <vector>
+#include "type.hpp"
+
+namespace lily {
+    class type_manager {
+        private:
+            int next_id;
+            std::vector<std::unique_ptr<type>> types;
+            std::map<std::string, type*> type_names;
+        public:
+            type_manager();
+
+            type_internal* create_int_type();
+            type_internal* create_str_type();
+            type_data* create_data_type(const std::string& name);
+
+            type* require_type(const std::string& name);
+    };
+}