Fix scastToMixed

The previous implementation failed when any of sh' was Unknown, which
makes no sense.

1 files changed, 5 insertions, 5 deletions

diff --git a/src/Data/Array/Nested/Internal/Shaped.hs b/src/Data/Array/Nested/Internal/Shaped.hs
index 2a8c206..f8df5aa 100644
--- a/src/Data/Array/Nested/Internal/Shaped.hs
+++ b/src/Data/Array/Nested/Internal/Shaped.hs
@@ -488,8 +488,8 @@ stoMixed (Shaped arr) = arr
 -- compatibility check.
 scastToMixed :: forall sh sh' a. (Elt a, Rank sh ~ Rank sh')
              => IShX sh' -> Shaped sh a -> Mixed sh' a
-scastToMixed shx (Shaped arr) =
-  case shxEqual shx (mshape arr) of
-    Just Refl -> arr
-    Nothing -> error $ "scastToMixed: Given shape (" ++ show shx ++ ") is not equal to " ++
-                       "the shape of the array (" ++ show (mshape arr) ++ ")"
+scastToMixed shx sarr@(Shaped arr)
+  | Refl <- lemAppNil @sh'
+  , Refl <- lemAppNil @(MapJust sh)
+  , Refl <- lemRankMapJust (sshape sarr)
+  = mcast (ssxFromShape (mshape arr)) shx (Proxy @'[]) arr