[css-counter-styles] handling of syntax errors in descriptors

http://dev.w3.org/csswg/css-counter-styles/#the-counter-style-rule
says:
  # When a given descriptor occurs multiple times in a given
  # @counter-style rule, only the last specified value is used; all
  # prior values for that descriptor must be ignored. 
and then later says:
  # Any descriptors that are not recognized or implemented by a
  # given user agent must be ignored in their entirety; they do not
  # make the @counter-style rule invalid.

It doesn't, however, say what happens for descriptors whose values
contain syntax unrecognized by the user agent.  (Or is the "not
recognized" intended to refer to the descriptor's value rather than
just the descriptor?)

I would normally expect descriptors containing unrecognized syntax
to be ignored, and I would normally expect this ignoring to happen
*before* the "last descriptor wins" processing happens, so that a
later descriptor with unrecognized syntax doesn't override an
earlier descriptor with recognized syntax.  That said, it's possible
there are reasons to differ from normal CSS practice here; I haven't
thought much about the issue.

Either way, though, the spec should say what happens when a
descriptor has a syntactically incorrect value.

-David

-- 
𝄞   L. David Baron                         http://dbaron.org/   𝄂
𝄢   Mozilla                          https://www.mozilla.org/   𝄂
             Before I built a wall I'd ask to know
             What I was walling in or walling out,
             And to whom I was like to give offense.
               - Robert Frost, Mending Wall (1914)