diff --git a/compiler/include/AST/Def.h b/compiler/include/AST/Def.h
index 23f9c3f..9fa74d6 100644
--- a/compiler/include/AST/Def.h
+++ b/compiler/include/AST/Def.h
@@ -11,9 +11,12 @@
 
 #include "Stmt/ExprStmt.h"
 #include "Stmt/FnDecl.h"
+#include "Stmt/TraitDecl.h"
+#include "Stmt/TypeDecl.h"
 #include "Stmt/ValDecl.h"
 
 #include "Type/Function.h"
+#include "Type/Generic.h"
 #include "Type/Named.h"
 #include "Type/Tuple.h"
 
diff --git a/compiler/include/AST/Expr/Call.h b/compiler/include/AST/Expr/Call.h
index 1f4a833..2d9cf7e 100644
--- a/compiler/include/AST/Expr/Call.h
+++ b/compiler/include/AST/Expr/Call.h
@@ -13,6 +13,7 @@ namespace ast
 
     ~CallExpr()
     {
+      delete callee;
       for (auto &arg : args)
         delete arg;
     }
diff --git a/compiler/include/AST/Expr/Closure.h b/compiler/include/AST/Expr/Closure.h
new file mode 100644
index 0000000..a8e6732
--- /dev/null
+++ b/compiler/include/AST/Expr/Closure.h
@@ -0,0 +1,19 @@
+#pragma once
+
+#include "AST/Base.h"
+#include <string>
+#include <vector>
+
+namespace ast
+{
+  class Closure : public Expr
+  {
+  public:
+    Closure(const std::vector<std::string> &args, const Expr *body)
+        : args(std::move(args)), body(body) {}
+    ~Closure() { delete body; }
+
+    const std::vector<std::string> args;
+    const Expr *body;
+  };
+}
\ No newline at end of file
diff --git a/compiler/include/AST/Stmt/TraitDecl.h b/compiler/include/AST/Stmt/TraitDecl.h
new file mode 100644
index 0000000..2d0f20b
--- /dev/null
+++ b/compiler/include/AST/Stmt/TraitDecl.h
@@ -0,0 +1,25 @@
+#pragma once
+
+#include "AST/Base.h"
+#include <vector>
+#include <string>
+
+namespace ast
+{
+  class FnDecl;
+
+  class TraitDecl : public Stmt
+  {
+  public:
+    TraitDecl(const std::string &name, const std::vector<FnDecl *> &traits)
+        : name(name), traits(std::move(traits)) {}
+    ~TraitDecl()
+    {
+      for (auto &trait : traits)
+        delete trait;
+    }
+
+    const std::string name;
+    const std::vector<FnDecl *> traits;
+  };
+}
\ No newline at end of file
diff --git a/compiler/include/AST/Stmt/TypeDecl.h b/compiler/include/AST/Stmt/TypeDecl.h
new file mode 100644
index 0000000..1778fce
--- /dev/null
+++ b/compiler/include/AST/Stmt/TypeDecl.h
@@ -0,0 +1,31 @@
+#pragma once
+
+#include "AST/Base.h"
+#include <vector>
+#include <string>
+
+namespace ast
+{
+  class FnDecl;
+
+  typedef std::pair<std::string, Type *> TypeAttr;
+
+  class TypeDecl : public Stmt
+  {
+  public:
+    TypeDecl(const std::string &name, const std::vector<TypeAttr> &attrs, const std::vector<FnDecl *> &members)
+        : name(name), attrs(std::move(attrs)), members(std::move(members)) {}
+    ~TypeDecl()
+    {
+      for (auto &attr : attrs)
+        delete attr.second;
+
+      for (auto &member : members)
+        delete member;
+    }
+
+    const std::string name;
+    const std::vector<TypeAttr> attrs;
+    const std::vector<FnDecl *> members;
+  };
+}
\ No newline at end of file
diff --git a/compiler/include/AST/Type/Generic.h b/compiler/include/AST/Type/Generic.h
new file mode 100644
index 0000000..49b11e9
--- /dev/null
+++ b/compiler/include/AST/Type/Generic.h
@@ -0,0 +1,24 @@
+#pragma once
+
+#include "AST/Base.h"
+#include <string>
+#include <vector>
+
+namespace ast
+{
+  class GenericType : public Type
+  {
+  public:
+    GenericType(const std::string &name, const std::vector<Type *> &types)
+        : name(name), types(std::move(types)) {}
+
+    ~GenericType()
+    {
+      for (auto &type : types)
+        delete type;
+    }
+
+    const std::string name;
+    const std::vector<Type *> types;
+  };
+}
diff --git a/compiler/include/Parser.h b/compiler/include/Parser.h
new file mode 100644
index 0000000..1a289a1
--- /dev/null
+++ b/compiler/include/Parser.h
@@ -0,0 +1,18 @@
+#pragma once
+
+#include <string>
+
+#include "AST/Def.h"
+#include "parser.gen.h"
+
+class Parser
+{
+public:
+  Parser() {}
+
+  ast::Module *parse(const std::string &file, const std::stringstream &input);
+
+  std::string file;
+  yy::location location;
+  ast::Module *module;
+};
diff --git a/compiler/include/ParserDriver.h b/compiler/include/ParserDriver.h
deleted file mode 100644
index 4ee54f8..0000000
--- a/compiler/include/ParserDriver.h
+++ /dev/null
@@ -1,25 +0,0 @@
-#pragma once
-
-#include <string>
-
-#include "AST/Def.h"
-#include "parser.gen.h"
-
-class ParserDriver
-{
-public:
-  ParserDriver() {}
-  ~ParserDriver() { delete module; }
-
-  int parse(const std::string &input);
-
-  void startLexer();
-  void stopLexer();
-
-  std::string file;
-  yy::location location;
-  ast::Module *module;
-};
-
-#define YY_DECL yy::parser::symbol_type yylex(ParserDriver &driver)
-YY_DECL;
diff --git a/compiler/lexer.ll b/compiler/lexer.ll
index 16633e9..1afe54b 100644
--- a/compiler/lexer.ll
+++ b/compiler/lexer.ll
@@ -1,6 +1,9 @@
 %{
 #include "parser.gen.h"
-#include "ParserDriver.h"
+#include "Parser.h"
+
+#undef YY_DECL
+#define YY_DECL yy::parser::symbol_type yylex(Parser &driver)
 
 #define yyterminate() yy::parser::make_END(yy::location())
 
@@ -16,7 +19,7 @@ hexdigit    [0-9a-fA-F]
 
 letter      [a-zA-Z]
 
-opchar      ("+"|"-"|"*"|"/"|"%"|"!"|"&"|"$"|"§"|"|"|"="|"<"|">"|"?"|"~"|"#"|":"|"^"|"\\")
+opchar      ("+"|"-"|"*"|"/"|"%"|"!"|"&"|"$"|"§"|"|"|"="|"<"|">"|"?"|"~"|"#"|":"|"^"|"\\"|".")
 
 whitespace  [ \n\t\r\v]+
 
@@ -33,9 +36,9 @@ whitespace  [ \n\t\r\v]+
 {opchar}+     { std::string text = yytext;
                 if (text == "=") return _token(EQUALS);
                 if (text == "->") return _token(RARR);
+                if (text == ".") return _token(DOT);
                 return _token(OPERATOR); }
 
-"."           { return _token(DOT); }
 ","           { return _token(COMMA); }
 ";"           { return _token(SEMI); }
 "("           { return _token(LPAREN); }
@@ -62,9 +65,3 @@ whitespace  [ \n\t\r\v]+
 {whitespace}                  { ; }
 
 %%
-
-void ParserDriver::startLexer() {
-  yy_scan_string(this->file.data());
-}
-
-void ParserDriver::stopLexer() {}
diff --git a/compiler/parser.yy b/compiler/parser.yy
index f868a9c..3a9120f 100644
--- a/compiler/parser.yy
+++ b/compiler/parser.yy
@@ -19,14 +19,15 @@
 
 %code requires {
 #include "AST/Def.h"
-class ParserDriver;
+class Parser;
 }
 
-%lex-param { ParserDriver &driver }
-%parse-param { ParserDriver &driver }
+%lex-param { Parser &driver }
+%parse-param { Parser &driver }
 
 %code {
-#include "ParserDriver.h"
+#include "Parser.h"
+yy::parser::symbol_type yylex(Parser &driver);
 }
 
 %token <long> INT "integer literal"
@@ -70,7 +71,8 @@ class ParserDriver;
   blockStmt
 ;
 
-%type <ast::FnDecl *> extFnDecl fnDecl;
+%type <std::vector<ast::FnDecl *>> fnDecls fnDecls0;
+%type <ast::FnDecl *> fnDecl fnDef;
 %type <ast::ValDecl *> valDecl;
 
 %type <std::vector<ast::Type *>>
@@ -79,14 +81,9 @@ class ParserDriver;
   fnTypeArgs
 ;
 
-%type <ast::Type *>
-  type
-;
+%type <ast::Type *> type type1;
 
-%type <std::vector<ast::Expr *>>
-  exprs
-  args
-;
+%type <std::vector<ast::Expr *>> exprs args;
 
 %type <ast::Expr *>
   expr
@@ -98,10 +95,7 @@ class ParserDriver;
 ;
 
 %type <ast::FnArg> fnArg;
-%type <std::vector<ast::FnArg>>
-  fnArgs
-  fnArgs0
-;
+%type <std::vector<ast::FnArg>> fnArgs fnArgs0;
 
 %type <std::vector<std::string>>
   lambdaArgs
@@ -110,6 +104,7 @@ class ParserDriver;
 
 %type <std::string>
   moduleName
+  type0
   operator
   identifier
   keyword
@@ -121,11 +116,14 @@ class ParserDriver;
   imports
 ;
 
+%type <ast::TraitDecl *> traitDecl;
+%type <ast::TypeDecl *> typeDecl;
+
 %start module
 
 %%
 
-module: imports topLevelStmts { driver.module = new ast::Module($2); }
+module: imports topLevelStmts { driver.module = new ast::Module($1, $2); }
       ;
 
 
@@ -144,14 +142,15 @@ moduleName: identifier                  { $$ = $1; }
           | moduleName "." identifier   { $$ = $1 + $2 + $3; }
           ;
 
-
 topLevelStmts: topLevelStmt                 { $$.push_back($1); }
              | topLevelStmts topLevelStmt   { $1.push_back($2); $$ = std::move($1); }
              ;
 
-topLevelStmt: fnDecl      { $$ = $1; }
-            | extFnDecl   { $$ = $1; }
+topLevelStmt: fnDef       { $$ = $1; }
+            | fnDecl      { $$ = $1; }
             | valDecl     { $$ = $1; }
+            | typeDecl    { $$ = $1; }
+            | traitDecl   { $$ = $1; }
             ;
 
 blockStmts: blockStmt              { $$.push_back($1); }
@@ -159,19 +158,33 @@ blockStmts: blockStmt              { $$.push_back($1); }
           ;
 
 blockStmt: valDecl    { $$ = $1; }
-         | fnDecl     { $$ = $1; }
+         | fnDef      { $$ = $1; }
          | expr ";"   { $$ = new ast::ExprStmt($1); }
          ;
 
+traitDecl: TRAIT identifier "=" "{" fnDecls "}"   { $$ = new ast::TraitDecl($2, $5); }
+         ;
+
+typeDecl: TYPE identifier "=" "(" fnArgs ")" "{" fnDecls "}"   { $$ = new ast::TypeDecl($2, $5, $8); }
+        ;
+
+fnDecls: %empty   { ; }
+       | fnDecls0 { $$ = std::move($1); }
+       ;
+
+fnDecls0: fnDecl            { $$.push_back($1); }
+        | fnDecls0 fnDecl   { $1.push_back($2); $$ = std::move($1); }
+        ;
+
 valDecl: VAL identifier "=" expr ";"        { $$ = new ast::ValDecl($2, nullptr, $4); }
        | VAL identifier type "=" expr ";"   { $$ = new ast::ValDecl($2, $3, $5); }
        ;
 
-fnDecl: FN identifier "[" fnArgs "]" type "=" expr ";"  { $$ = new ast::FnDecl($2, $4, $6, $8); }
+fnDef : FN identifier "[" fnArgs "]" type "=" expr ";"  { $$ = new ast::FnDecl($2, $4, $6, $8); }
       ;
 
-extFnDecl: DECLARE FN identifier "[" fnArgs "]" type ";"  { $$ = new ast::FnDecl($3, $5, $7, nullptr); }
-         ;
+fnDecl: FN identifier "[" fnArgs "]" type ";"  { $$ = new ast::FnDecl($2, $4, $6, nullptr); }
+      ;
 
 fnArgs: %empty    { ; }
       | fnArgs0   { $$ = std::move($1); }
@@ -188,12 +201,18 @@ types: type             { $$.push_back($1); }
      | types "," type   { $1.push_back($3); $$ = std::move($1); }
      ;
 
-type: identifier                     { $$ = new ast::NamedType($1); }
+type: type1
     | "(" type ")"                   { $$ = $2; }   
     | "(" tupleTypes ")"             { $$ = new ast::TupleType($2); }
     | "[" fnTypeArgs "]" "->" type   { $$ = new ast::FunctionType($2, $5); }
     ;
 
+type1: type0                { $$ = new ast::NamedType($1); }
+     | type0 "{" types "}"  { $$ = new ast::GenericType($1, $3); }
+     ;
+
+type0: identifier;
+
 tupleTypes: type "," type             { $$.push_back($1); $$.push_back($3); }
           | tupleTypes "," type       { $1.push_back($3); $$ = std::move($1); }
           ;
@@ -210,8 +229,8 @@ expr: expr3 { $$ = $1; }
     ;
 
 expr3: expr2                          { $$ = $1; }
-     | "[" lambdaArgs "]" "->" expr   { $$ = NULL; }
-     | "{" blockStmts "}"                  { $$ = new ast::BlockExpr($2); }
+     | "[" lambdaArgs "]" "->" expr   { $$ = nullptr; }
+     | "{" blockStmts "}"             { $$ = new ast::BlockExpr($2); }
      ;
 
 expr2: expr1                  { $$ = $1; }
@@ -226,6 +245,7 @@ expr0: literal              { $$ = $1; }
      | identifier           { $$ = new ast::Identifier($1); }
      | expr0 "[" args "]"   { $$ = new ast::CallExpr($1, $3); }
      | "(" expr ")"         { $$ = new ast::PrefExpr($2); }
+     | expr0 "." identifier { $$ = $1; }
      ;
 
 lambdaArgs: %empty        { ; }
diff --git a/compiler/src/Parser.cpp b/compiler/src/Parser.cpp
new file mode 100644
index 0000000..b42ce60
--- /dev/null
+++ b/compiler/src/Parser.cpp
@@ -0,0 +1,20 @@
+#include "Parser.h"
+
+#include <sstream>
+#include <fstream>
+
+void yy_scan_string(const char *);
+
+ast::Module *Parser::parse(const std::string &file, const std::stringstream &input)
+{
+  module = nullptr;
+
+  this->file = file;
+  location.initialize(&file);
+
+  yy_scan_string(input.str().data());
+
+  int res = yy::parser(*this)();
+
+  return module;
+}
diff --git a/compiler/src/ParserDriver.cpp b/compiler/src/ParserDriver.cpp
deleted file mode 100644
index ecefb55..0000000
--- a/compiler/src/ParserDriver.cpp
+++ /dev/null
@@ -1,14 +0,0 @@
-#include "ParserDriver.h"
-
-int ParserDriver::parse(const std::string &input)
-{
-  file = input;
-  location.initialize(&file);
-
-  startLexer();
-  yy::parser parse(*this);
-  int res = parse();
-  stopLexer();
-
-  return res;
-}
diff --git a/compiler/src/main.cpp b/compiler/src/main.cpp
index e2ede87..0b8326e 100644
--- a/compiler/src/main.cpp
+++ b/compiler/src/main.cpp
@@ -1,10 +1,10 @@
-#include "ParserDriver.h"
+#include "Parser.h"
 
 #include <iostream>
 #include <fstream>
 #include <sstream>
 
-std::stringstream readFile(const std::string &path)
+static std::stringstream readFile(const std::string &path)
 {
   std::ifstream t(path);
   std::stringstream buffer;
@@ -21,10 +21,10 @@ int main(int argc, char *argv[])
     exit(EXIT_FAILURE);
   }
 
-  auto buf = readFile(argv[1]);
-  auto parser = ParserDriver();
-  parser.parse(buf.str());
+  auto module = Parser().parse(argv[1], readFile(argv[1]));
 
-  auto fn = (ast::FnDecl *)parser.module->stmts.at(0);
+  auto fn = (ast::FnDecl *)module->stmts.at(0);
   std::cout << fn->name << std::endl;
+
+  delete module;
 }
diff --git a/examples/42.plsm b/examples/42.plsm
index 1c55ef4..0df96c2 100644
--- a/examples/42.plsm
+++ b/examples/42.plsm
@@ -3,7 +3,9 @@ import test.test;
 fn main[] Int = 42;
 
 fn test[b Int] Int = {
-  fn helper[] Int = 10;
-  20 * b;
+  fn helper[] Int = b;
+  20 * helper[];
 };
 
+fn size[vals List{Int}] Int = vals.size[];
+
diff --git a/lib/include/types/types.h b/lib/include/types/types.h
index 199b1a4..6c5abd6 100644
--- a/lib/include/types/types.h
+++ b/lib/include/types/types.h
@@ -1,4 +1,4 @@
 #pragma once
 
 #include "int.h"
-#include "bool.h"
\ No newline at end of file
+#include "bool.h"