TYPO3 Core

Btw, simply adding an "implements ..." line to the class declaration leads to bugs in the output.

Yes. This is not only this specific view helper, there are much more. I'm currently working on a fresh backport from TYPO3.fluid that has much more compilable interfaces implemented already, you can expect a patch in this area soon.

if backport is done, a couple of other view helpers that did not yet have been fixed in fluid upstream will be changed for cms core locally. the performance boost is just too high to wait for upstream at this point ... give me some time and expect this issue to be fixed soon. i'll ping you for reviews if you find the time, Christian.

Hi,

that is a problem indeed. The actual issue is not that the ViewHelper itself is not compilable, but that it also implements the {ChildNodeAccessInterface}} which - in combination - leads to the whole template file not being compiled. (see https://jira.typo3.org/browse/FLOW-224).
BTW: The same is true when using widgets, but in those cases the issue is probably very hard to solve unfortunately (see https://jira.typo3.org/browse/FLOW-196).