[css3-values] calc() constraints too strong for * and /

In the new text in
http://dev.w3.org/csswg/css3-values/#the-calc-min-and-max-functions
describing calc(), I think these constraints:
  > 2. At "*":
  > check: at least one side is "number"
  > return: the type of the other side
  > 3. At "/":
  > check: either right side is "number," or both have the same type
  > return: if the former, type of left side; otherwise "number" 
are too strong.  And, additionally, since the new definition of the
binary operators is nonrecursive, they're also ambiguous.

In particular, I think it's bad that they make:
  2em * (2em / 3em)
legal while the mathematically equivalent:
  (2em * 2em) / 3em
is illegal and it's unclear whether:
  2em * 2em / 3em
is legal or not.  I think these should be handled consistently.


That said, in my implementation in Gecko I'm not implementing
division by values at this time.

-David

-- 
L. David Baron                                 http://dbaron.org/
Mozilla Corporation                       http://www.mozilla.com/