• Type constructor ‘Matrix’ used where a value identifier was expected
    • In the expression: ((Matrix (1, 2)) [[a, b]] :: Matrix 1 2 Int)
      In an equation for ‘it’:
          it = ((Matrix (1, 2)) [[a, b]] :: Matrix 1 2 Int)

. let v = (AppE (AppE (ConE ''Matrix) (TupE [LitE $ IntegerL m, LitE $ IntegerL n])) (ListE $ map ListE matrix))
  let t = (AppT (AppT (AppT (ConT ''Matrix) (LitT (NumTyLit m))) (LitT (NumTyLit n))) mType)
  pure $ SigE v t

data Matrix (m :: Nat) (n :: Nat) a where
  Matrix :: (Int, Int) -> [[a]] -> Matrix m n a
  E :: Num a => a -> Matrix n n a
  Z :: Num a => Matrix m n a

a = 5 :: Int 
b = 6 :: Int
[matrix| a b |]

matrix :: QuasiQuoter
matrix =
  QuasiQuoter
    { quoteExp = expr
    , quotePat = undefined
    , quoteType = undefined
    , quoteDec = undefined
    }

expr :: String -> Q Exp
expr source = do
  let matrix =
        case traverse (traverse parseExp . words) $
             filter (not . null) $ lines source of
          Right ok -> ok
          Left err -> error $ "MatrixTH parse error: " <> err
  mType <- resolveType $ concat matrix
  let m = fromIntegral $ length matrix
  let n =
        let lengths = map length matrix
         in if allEq lengths
              then fromIntegral $ maybe 0 id $ listToMaybe lengths
              else error "MatrixTH all lines must be same length"
  let v = (AppE (AppE (ConE ''Matrix) (TupE [LitE $ IntegerL m, LitE $ IntegerL n])) (ListE $ map ListE matrix))
  let t = (AppT (AppT (AppT (ConT ''Matrix) (LitT (NumTyLit m))) (LitT (NumTyLit n))) mType)
  pure $ SigE v t

λ > m = [matrix| a b |]

<interactive>:17:13: error:
    • Type constructor ‘Matrix’ used where a value identifier was expected
    • In the expression: ((Matrix (1, 2)) [[a, b]] :: MatrixT 1 2 Int)
      In an equation for ‘m’:
          m = ((Matrix (1, 2)) [[a, b]] :: MatrixT 1 2 Int)