It's the same as doing

<xsl:if test="false()">
  <xsl:value-of select="2 + 'London'"/>
</xsl:if>

Specifically: if there's a type error in an expression that would cause it
inevitably to fail if executed, then a static error can be reported
regardless of the fact that the expression will in fact not be executed.
Without this rule, you would get far fewer compile-time errors, which would
not be a good thing.

I presume this is actually generated code, since I can't imagine any
intelligent human writing it (unless perhaps to test the behaviour of the
processor). It's certainly true that type-checking rules make it harder to
generate code that will get through the compiler, but I think that's a price
worth paying.

Michael Kay
http://www.saxonica.com/
 

> -----Original Message-----
> From: Costello, Roger L. [mailto:costello@xxxxxxxxx] 
> Sent: 28 April 2008 21:21
> To: xsl-list@xxxxxxxxxxxxxxxxxxxxxx
> Subject:  Problem with iterating through a sequence of integers
> 
> Hi Folks,
> 
> Consider this for-loop which iterates through a sequence.  If 
> the sequence value is a node then apply-templates is called.  
> Otherwise, the value is output:
> 
>     <xsl:for-each select="(1, 2, 3)">
>         <xsl:choose>
>             <xsl:when test=". instance of node()">
>                 <xsl:apply-templates select="." />
>             </xsl:when>
>             <xsl:otherwise>
>                 <xsl:value-of select="."/>
>             </xsl:otherwise>
>         </xsl:choose>
>     </xsl:for-each>
> 
> When I run Saxon, I get this error message:
> 
> 
> Error: Required item type of @select attribute of 
> xsl:apply-templates is node(); supplied value has item type 
> xs:integer Failed to compile stylesheet. 1 error detected.
> 
> 
> If I comment out the apply-templates statement, the for-loop works
> fine.
> 
> It also works fine if I add a node to the for-loop's XPath expression,
> e.g.
> 
>     <xsl:for-each select="(//Book/Author, 1, 2, 3)">
> 
> I'm baffled.  Any ideas?
> 
> /Roger