anchor.diff:  ==== Syntax restriction
   
   The rewrite does not cover all syntactically possible queries.
  +Specifically, any <ProjectItems> containing
  +
  +* an aggregation function and
  +* a sub-expression that is
  +** outside any contained aggregation function and
  +** not constant under the grouping keys
  +
  +is not rewritten to valid query.
   
   .Aggregation *not* covered by the rewrite
   ====
   
  -By the proposed semantics, the RETURN clause
  +By the grouping and aggregation semantics, the RETURN clause
   
   .[[Q6]]Q6
   [source, cypher]
  
positive.code: RETURN a AS a, b + SUM(c) * 2 AS foo
  ----
  
  is defined as effectively equivalent to
  
  [source, cypher]
  ----
  
negative.code: RETURN POST_PROJ(_L_)
  ----
  
  Analogously, `WITH _L_` is effectively equivalent to
  
  [source, cypher, subs="quotes"]
  ----
  