svoid tok_swingBlocks(LS tok) {
  replaceKeywordBlock_dyn(tok,
    "swing", (_tok, iOpening, iClosing) ->
      containsReturnWithArgument(subList(tok, iOpening+1, iClosing))
        ? litstringarray("{ ret swing(-> {", "}); }")
        : litstringarray("{ swing(-> {", "}); }")
  );
}