[Bug 3717] Cardinality inference for 'cast as' should take operand into account

http://www.w3.org/Bugs/Public/show_bug.cgi?id=3717





------- Comment #3 from simeon@us.ibm.com  2006-09-18 23:48 -------
It seems that if users are able to write functions like that:

xs:date(if (cond()) then () else "1999-12-31")

then static typing must be consistent with the dynamic semantics.

Another example is when using arithmetics:

declare function mycast($floatvalue as xs:float?) as xs:decimal? {
  xs:decimal($floatvalue * 0.2E-5)
};

So either such queries should type check (which is what currently happens), or
someone has to decide that constructors functions cannot take an empty
sequence.

Either way, I think either change is too big for the stage of development
XQuery
is right now.

- Jerome