It was not accurate. Placeholders could be used in outputs that are
defined in the same mapping as long as that placeholder does not do the
same.
A more general solution would be to detect it at run-time in the
replacer directly, but that's a bit tedious
and will require allocations I think.
A better implementation of this check could still be done, but I don't
know if it would always be accurate. Could be a "best-effort" thing?
But I've also never heard of an actual case where someone configured
infinite recursion...
