diff --git a/Grammar.cf b/Grammar.cf
index 540052f..b0a7a4c 100644
--- a/Grammar.cf
+++ b/Grammar.cf
@@ -45,30 +45,31 @@ Data. Data ::= "data" Type "where" "{" [Constructor] "}" ;
 
 EAnn.   Exp5 ::= "(" Exp ":" Type ")" ;
 EVar.   Exp4 ::= LIdent ;
-ECons.  Exp4 ::= UIdent ;
+EInj.   Exp4 ::= UIdent ;
 ELit.   Exp4 ::= Lit ;
 EApp.   Exp3 ::= Exp3 Exp4 ;
 EAdd.   Exp1 ::= Exp1 "+" Exp2 ;
 ELet.   Exp  ::= "let" Bind "in" Exp ; 
 EAbs.   Exp  ::= "\\" LIdent "." Exp ;
-ECase.  Exp  ::= "case" Exp "of" "{" [Inj] "}";
+ECase.  Exp  ::= "case" Exp "of" "{" [Branch] "}";
 
 -------------------------------------------------------------------------------
 -- * LITERALS
 -------------------------------------------------------------------------------
 
-LInt. Lit  ::= Integer ;
+LInt.  Lit ::= Integer ;
 LChar. Lit ::= Char ;
 
 -------------------------------------------------------------------------------
 -- * CASE
 -------------------------------------------------------------------------------
 
-Inj. Inj ::= Init "=>" Exp ;
+Branch. Branch ::= Pattern "=>" Exp ;
 
-InitLit. Init         ::= Lit ;
-InitConstructor. Init ::= UIdent [LIdent] ;
-InitCatch. Init       ::= "_" ;
+PVar.   Pattern ::= LIdent ;
+PLit.   Pattern ::= Lit ;
+PInj.   Pattern ::= UIdent [Pattern] ;
+PCatch. Pattern ::= "_" ;
 
 -------------------------------------------------------------------------------
 -- * AUX
@@ -77,7 +78,8 @@ InitCatch. Init       ::= "_" ;
 separator Def ";" ;
 separator nonempty Constructor "" ;
 separator Type " " ;
-separator nonempty Inj ";" ;
+separator Pattern " " ;
+separator Branch "," ;
 separator Ident " ";
 separator LIdent " ";
 separator TVar " " ;
diff --git a/src/TypeChecker/TypeCheckerIr.hs b/src/TypeChecker/TypeCheckerIr.hs
index ceac8e9..09efb8b 100644
--- a/src/TypeChecker/TypeCheckerIr.hs
+++ b/src/TypeChecker/TypeCheckerIr.hs
@@ -2,7 +2,6 @@
 
 module TypeChecker.TypeCheckerIr (
     module TypeChecker.TypeCheckerIr,
-    module GA,
 ) where
 
 import Control.Monad.Except
@@ -10,18 +9,7 @@ import Control.Monad.Reader
 import Control.Monad.State
 import Data.Functor.Identity (Identity)
 import Data.Map (Map)
-import Grammar.Abs (
-    Data (..),
-    Ident (..),
-    Init (..),
-    Lit (..),
- )
-import Grammar.Abs qualified as GA (
-    Data (..),
-    Ident (..),
-    Init (..),
-    Lit (..),
- )
+import Data.String qualified
 import Grammar.Print
 import Prelude
 import Prelude qualified as C (Eq, Ord, Read, Show)
@@ -44,6 +32,12 @@ type Infer = StateT Env (ReaderT Ctx (ExceptT Error Identity))
 newtype Program = Program [Def]
     deriving (C.Eq, C.Ord, C.Show, C.Read)
 
+data Data = Data Ident [Constructor]
+    deriving (Show, Eq, Ord, Read)
+
+data Constructor = Constructor Ident Type
+    deriving (Show, Eq, Ord, Read)
+
 newtype TVar = MkTVar Ident
     deriving (Show, Eq, Ord, Read)
 
@@ -62,26 +56,51 @@ data Exp
     | EApp ExpT ExpT
     | EAdd ExpT ExpT
     | EAbs Ident ExpT
-    | ECase ExpT [Inj]
+    | ECase ExpT [Branch]
     deriving (C.Eq, C.Ord, C.Read, C.Show)
 
 type ExpT = (Exp, Type)
 
-data Inj = Inj (Init, Type) ExpT
+data Branch = Branch (Pattern, Type) ExpT
     deriving (C.Eq, C.Ord, C.Read, C.Show)
 
+data Pattern = PVar Id | PLit (Lit, Type) | PInj Ident [Pattern] | PCatch
+    deriving (C.Eq, C.Ord, C.Show, C.Read)
+
 data Def = DBind Bind | DData Data
     deriving (C.Eq, C.Ord, C.Read, C.Show)
 
 type Id = (Ident, Type)
 
+newtype Ident = Ident String
+    deriving (C.Eq, C.Ord, C.Show, C.Read, Data.String.IsString)
+
+data Lit = LInt Integer | LChar Char
+    deriving (Show, Eq, Ord, Read)
+
 data Bind = Bind Id [Id] ExpT
     deriving (C.Eq, C.Ord, C.Show, C.Read)
 
+instance Print Ident where
+    prt _ (Ident str) = prt 0 str
+
 instance Print [Def] where
     prt _ [] = concatD []
     prt _ (x : xs) = concatD [prt 0 x, doc (showString "\n\n"), prt 0 xs]
 
+instance Print Data where
+    prt i = \case
+        Data type_ constructors -> prPrec i 0 (concatD [doc (showString "data"), prt 0 type_, doc (showString "where"), doc (showString "{"), prt 0 constructors, doc (showString "}")])
+
+instance Print Constructor where
+    prt i = \case
+        Constructor uident type_ -> prPrec i 0 (concatD [prt 0 uident, doc (showString ":"), prt 0 type_])
+
+instance Print [Constructor] where
+    prt _ [] = concatD []
+    prt _ [x] = concatD [prt 0 x]
+    prt _ (x : xs) = concatD [prt 0 x, prt 0 xs]
+
 instance Print Def where
     prt i (DBind bind) = prt i bind
     prt i (DData d) = prt i d
@@ -185,11 +204,18 @@ instance Print Exp where
 instance Print ExpT where
     prt i (e, t) = concatD [doc $ showString "(", prt i e, doc (showString ":"), prt i t, doc $ showString ")"]
 
-instance Print Inj where
+instance Print Branch where
     prt i = \case
-        Inj (init, t) exp -> prPrec i 0 (concatD [prt 0 init, doc (showString ":"), prt 0 t, doc (showString "=>"), prt 0 exp])
+        Branch (init, t) exp -> prPrec i 0 (concatD [prt 0 init, doc (showString ":"), prt 0 t, doc (showString "=>"), prt 0 exp])
 
-instance Print [Inj] where
+instance Print Pattern where
+    prt i = \case
+        PVar lident -> prPrec i 0 (concatD [prtId 0 lident])
+        PLit (lit, typ) -> prPrec i 0 (concatD [doc $ showString "(", prt 0 lit, doc $ showString ",", prt 0 typ, doc $ showString ")"])
+        PInj uident patterns -> prPrec i 0 (concatD [prt 0 uident, prt 0 patterns])
+        PCatch -> prPrec i 0 (concatD [doc (showString "_")])
+
+instance Print [Branch] where
     prt _ [] = concatD []
     prt _ [x] = concatD [prt 0 x]
     prt _ (x : xs) = concatD [prt 0 x, doc (showString ";"), prt 0 xs]
@@ -204,3 +230,8 @@ instance Print Type where
         TAll tvar type_ -> prPrec i 1 (concatD [doc (showString "forall"), prt 0 tvar, doc (showString "."), prt 0 type_])
         TData ident types -> prPrec i 1 (concatD [prt 0 ident, prt 0 types])
         TFun type_1 type_2 -> prPrec i 0 (concatD [prt 1 type_1, doc (showString "->"), prt 0 type_2])
+
+instance Print Lit where
+    prt i = \case
+        LInt n -> prPrec i 0 (concatD [prt 0 n])
+        LChar c -> prPrec i 0 (concatD [prt 0 c])