eval :: TileQuery -> Config -> World -> TileQueryResult
eval (QRef sr tr) c wo = nonHists $ do
  sr' <- evalSR c wo sr
  evalTR c wo sr' tr
eval :: TileQuery -> Config -> World -> TileQueryResult
eval (QRef sr tr) c wo = nonHists $ do
  sr' <- evalSR c wo sr
  evalTR c wo sr' tr
eval (QRef sr tr) c wo = nonHists $ do
  sr' <- evalSR c wo sr
  evalTR c wo sr' tr