Saxon

The problem is that this:

                <xsl:copy select="$root">
                    <xsl:copy-of select="current-group()"/>
                </xsl:copy>

is rewritten internally as

           <xsl:for-each select="$root">
                <xsl:copy>
                    <xsl:copy-of select="current-group()"/>
                </xsl:copy>
            </xsl:for-each>

giving the impression that the current-group() instruction is evaluated repeatedly.

Marking this as "AwaitingInfo" since it is dependent on resolution of W3C bug 29482.

The XSL WG resolved bug 29482 by deciding that this case was not streamable; so there is no bug here.