mkVectEnv :: [Type] -> [Var] -> (Type, CoreExpr, CoreExpr -> CoreExpr -> CoreExpr)
mkVectEnv [] [] = (unitTy, Var unitDataConId, \_ body -> body)
mkVectEnv :: [Type] -> [Var] -> (Type, CoreExpr, CoreExpr -> CoreExpr -> CoreExpr)
mkVectEnv [] [] = (unitTy, Var unitDataConId, \_ body -> body)