1 files changed, 22 insertions, 8 deletions
diff --git a/src/HSVIS/AST.hs b/src/HSVIS/AST.hs
index 5a90205..f606d22 100644
--- a/src/HSVIS/AST.hs
+++ b/src/HSVIS/AST.hs
@@ -1,3 +1,7 @@
+{-# LANGUAGE DataKinds #-}
+{-# LANGUAGE GADTs #-}
+{-# LANGUAGE KindSignatures #-}
+{-# LANGUAGE StandaloneDeriving #-}
 module HSVIS.AST where
 
 import Data.List.NonEmpty (NonEmpty)
@@ -17,18 +21,27 @@ data DataDef = DataDef Name [Name] [(Name, [Type])]
 data FunDef t = FunDef Name (Maybe Type) (NonEmpty (FunEq t))
   deriving (Show)
 
-data FunEq t = FunEq Name [Pattern t] (RHS t)
+data FunEq t = FunEq t Name [Pattern t] (RHS t)
   deriving (Show)
 
-data Type
-  = TApp Type [Type]
-  | TTup [Type]
-  | TList Type
-  | TFun Type Type
-  | TCon Name
-  | TVar Name
+data TypeStage = TSTC | TSNormal
   deriving (Show)
 
+data GType (stage :: TypeStage) where
+  TApp :: GType s -> [GType s] -> GType s
+  TTup :: [GType s] -> GType s
+  TList :: GType s -> GType s
+  TFun :: GType s -> GType s -> GType s
+  TCon :: Name -> GType s
+  TVar :: Name -> GType s
+
+  -- Type constructor used only while type checking
+  TUniVar :: Int -> GType 'TSTC
+deriving instance Show (GType stage)
+
+type TCType = GType 'TSTC
+type Type = GType 'TSNormal
+
 data Pattern t
   = PWildcard t
   | PVar t Name
@@ -55,6 +68,7 @@ data Expr t
   | EIf t (Expr t) (Expr t) (Expr t)
   | ECase t (Expr t) [(Pattern t, RHS t)]
   | ELet t [FunDef t] (Expr t)
+  | EParseError
   deriving (Show)
 
 data Literal = LInt Integer | LFloat Rational | LChar Char | LString String