[xsl] [XSLT 3.0]

[sean@xxxxxxxxxxxxxxxxx]

Suppose that $state is a sequence which contains, among other things, 
at least one function item with signature...

   function(element(square)*) as element(square)*

Which is the correct and safe way to store a reference to this function 
in a variable?

Is it OPTION A?

    <xsl:variable name="compute-possible-moves"
         select="$state[. instance of function(*)][1]"
         as="function(element(square)*) as element(square)*">

... OR OPTION B?

    <xsl:variable name="compute-possible-moves"
         select="$state[. instance of function(*)][1]
                 treat as function(element(square)*) as 
element(square)*"">

... OR OPTION C?

    <xsl:variable name="compute-possible-moves"
         select="$state[. instance of function(*)][1]
                 treat as function(element(square)*) as 
element(square)*"
         as="function(element(square)*) as element(square)*">

My best estimate at the moment, would be option A, but I am not really 
sure about it.


Faithfully,
Sean B. Durkin