Let sh*FromList functions print proper error messages

1 files changed, 8 insertions, 5 deletions

diff --git a/src/Data/Array/Nested/Ranked/Shape.hs b/src/Data/Array/Nested/Ranked/Shape.hs
index 02d65b6..2fea8c4 100644
--- a/src/Data/Array/Nested/Ranked/Shape.hs
+++ b/src/Data/Array/Nested/Ranked/Shape.hs
@@ -130,11 +130,14 @@ listrAppend ZR sh = sh
 listrAppend (x ::: xs) sh = x ::: listrAppend xs sh
 
 listrFromList :: SNat n -> [i] -> ListR n i
-listrFromList SZ [] = ZR
-listrFromList (SS n) (i : is) = i ::: listrFromList n is
-listrFromList n l = error $ "listrFromList: Mismatched list length (type says "
-                            ++ show (fromSNat n) ++ ", list has length "
-                            ++ show (length l) ++ ")"
+listrFromList topsn topl = go topsn topl
+  where
+    go :: SNat n' -> [i] -> ListR n' i
+    go SZ [] = ZR
+    go (SS n) (i : is) = i ::: go n is
+    go _ _ = error $ "listrFromList: Mismatched list length (type says "
+                     ++ show (fromSNat topsn) ++ ", list has length "
+                     ++ show (length topl) ++ ")"
 
 {-# INLINEABLE listrToList #-}
 listrToList :: ListR n i -> [i]