A GROUP BY key that is an expression can be selected and filtered on, but not ordered by.

SELECT b.primitiveInt \+ 1 FROM Item AS b GROUP BY b.primitiveInt \+ 1 ORDER BY b.primitiveInt \+ 1

throws FeatureNotSupportedException, while the equivalent over a column key works:

SELECT b.primitiveInt FROM Item AS b GROUP BY b.primitiveInt ORDER BY b.primitiveInt

Scope is ORDER BY an expression that is itself a GROUP BY key. Ordering by an arbitrary expression with no GROUP BY is HIBERNATE-79.