rewrote unification for data type and variable.

could definitely be wrong. have to double check

src/TypeChecker/TypeChecker.hs

@@ -83,7 +83,7 @@ checkPrg :: Program -> Infer T.Program
 checkPrg (Program bs) = do
     preRun bs
     -- Type check the program twice to produce all top-level types in the first pass through
-    bs' <- checkDef bs
+    _ <- checkDef bs
     bs'' <- checkDef bs
     return $ T.Program bs''
   where
@@ -132,7 +132,7 @@ checkBind err@(Bind name args e) = do
                 return $ T.Bind (apply sub (coerce name, newT)) (map coerce args) e
             _ -> do
                 insertSig (coerce name) (Just lambdaT)
-                return (T.Bind (coerce name, lambdaT) (map coerce args) e) -- (apply s e)
+                return (T.Bind (coerce name, lambdaT) (map coerce args) e)
 
 isMoreSpecificOrEq :: T.Type -> T.Type -> Bool
 isMoreSpecificOrEq _ (T.TAll _ _) = True
@@ -321,6 +321,9 @@ unify t0 t1 = do
             s1 <- unify a c
             s2 <- unify (apply s1 b) (apply s1 d)
             return $ s1 `compose` s2
+        -- TODO: BEWARY. THIS IS PROBABLY WRONG!!!
+        (T.TVar (T.MkTVar a), t@(T.TData _ _)) -> return $ M.singleton a t
+        (t@(T.TData _ _), T.TVar (T.MkTVar b)) -> return $ M.singleton b t
         (T.TVar (T.MkTVar a), t) -> occurs a t
         (t, T.TVar (T.MkTVar b)) -> occurs b t
         (T.TAll _ t, b) -> unify t b

src/TypeChecker/TypeCheckerIr.hs

@@ -7,6 +7,7 @@ module TypeChecker.TypeCheckerIr (
 import Control.Monad.Except
 import Control.Monad.Reader
 import Control.Monad.State
+import Data.Char (isDigit)
 import Data.Functor.Identity (Identity)
 import Data.Map (Map)
 import Data.String qualified
@@ -227,7 +228,10 @@ instance Print TVar where
 instance Print Type where
     prt i = \case
         TLit uident -> prPrec i 2 (concatD [prt 0 uident])
-        TVar tvar -> prPrec i 2 (concatD [prt 0 tvar])
+        TVar tvar@(MkTVar (Ident iden)) ->
+            if all isDigit iden
+                then prPrec i 2 (concatD [prt 0 $ TVar (MkTVar (Ident ("a" <> iden)))])
+                else prPrec i 2 (concatD [prt 0 tvar])
         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])

test_program

@@ -35,7 +35,12 @@ data List (a) where {
 
 -- main = firstIsOne (Cons 1 Nil);
 
-test xs = case xs of {
+-- test xs = case xs of {
-    1 => 0;
+--     1 => 0;
-    lol => 1;
+--     lol => 1;
+                     -- };
+
+deepList xs = case xs of {
+    Cons Nil _ => 1 ;
+    _ => 0 ;
 };