Infinite-ish recursion on singleton classes

[Roy-Orbison]

Using XDebug + PHP, going through some code that contains a singleton class leads to Vdebug crashes. They can take a long time to recover, and then immediately crash again on the next step. I can prevent the crash by doing :VdebugEval! $not_a_var but this of course kills watching all context. VDebug expands the local variable containing the instance, finds its class' static property holding the same reference, and repeats.

I imagine the simplest way to avoid this is to check if any property (static or otherwise) is a reference to itself/one of its (visible) parents, and not expand it.

[Roy-Orbison]

It also occurs on closures that use a reference to themselves, for intentional recursion.