XQuery 3.0 states that:

"The expression E castable as T returns true if the result of evaluating E can be successfully cast into the target type T by using a cast expression; otherwise it returns false. If evaluation of E fails with a dynamic error, the castable expression returns false. The castable expression can be used as a predicate to avoid errors at evaluation time. It can also be used to select an appropriate type for processing of a given value, as illustrated in the following example:"

Neither of the tests K2-SeqExprCastable-3 and -4 expect false, yet in each case the argument to castable raises an error.


   <test-case name="K2-SeqExprCastable-3">
      <description> Combine operator div with castable as. </description>
      <created by="Frans Englich" on="2007-11-26"/>
      <test>(1 div 0) castable as xs:string</test>
      <result>
          <any-of>
            <assert-true/><!-- permitted by errors-and-optimization -->
            <error code="FOAR0001"/>
          </any-of>
      </result>
   </test-case>

   <test-case name="K2-SeqExprCastable-4">
      <description> Combine operator div with castable as(#2). </description>
      <created by="Frans Englich" on="2007-11-26"/>
      <test>concat("2007-01-3", 1 div 0) castable as xs:date</test>
      <result>
         <error code="FOAR0001"/>
      </result>
   </test-case>