Fixed more precise type annotation for monomorphizer

src/TypeChecker/TypeCheckerHm.hs

@@ -7,7 +7,7 @@
 module TypeChecker.TypeCheckerHm where
 
 import Auxiliary (int, litType, maybeToRightM, unzip4)
-import qualified Auxiliary                 as Aux
+import Auxiliary qualified as Aux
 import Control.Monad.Except
 import Control.Monad.Identity (Identity, runIdentity)
 import Control.Monad.Reader
@@ -18,14 +18,14 @@ import           Data.Function             (on)
 import Data.List (foldl', nub, sortOn)
 import Data.List.Extra (unsnoc)
 import Data.Map (Map)
-import qualified Data.Map                  as M
+import Data.Map qualified as M
 import Data.Maybe (fromJust)
 import Data.Set (Set)
-import qualified Data.Set                  as S
+import Data.Set qualified as S
 import Debug.Trace (trace)
 import Grammar.Abs
 import Grammar.Print (printTree)
-import qualified TypeChecker.TypeCheckerIr as T
+import TypeChecker.TypeCheckerIr qualified as T
 
 {-
 TODO
@@ -168,6 +168,8 @@ checkBind (Bind name args e) = do
             let m1 = M.fromList $ zip fvs1 letters
             let t0 = replace m0 t'
             let t1 = replace m1 lambda_t
+            -- Not sure if this is actually correct
+            sub <- unify t' lambda_t
             unless
                 (t1 <<= t0)
                 ( throwError $
@@ -180,7 +182,9 @@ checkBind (Bind name args e) = do
                         )
                         False
                 )
-            return $ T.Bind (coerce name, t') [] (e, lambda_t)
+            -- Applying sub to t' will worsen error messages.
+            -- Unfortunately I do not know a better solution at the moment.
+            return $ T.Bind (coerce name, apply sub t') [] (apply sub e, lambda_t)
         _ -> do
             insertSig (coerce name) (Just lambda_t)
             return (T.Bind (coerce name, lambda_t) [] (e, lambda_t))