Comment 2 for bug 1714499

The bug is triggered by multiple subtractions in the same child in the query-xml.
We expected exactly two children for a <integer-difference>-expression -- the query-xml attached has three.

I have proposed a fix st. we parse expressions like

x - y -z

into pairwise form

(x - y) - z

with special case

- x

to

0 - x