anchor.diff:  . `MATCH (x) WITH x.a + x.b + x.c AS sum RETURN sum, sum + count(*) + sum`
   * The sub-expression `sum` is a grouping key.
   
  -==== Queries invalid under the grouping and aggregation semantics
  -
  -The following clauses are invalid under the grouping and aggregation semantics and the syntax restriction it includes.
  +==== Invalid aggregations
  +
  +The following clauses exhibit invalid aggregations under the grouping and aggregation semantics and the syntax restriction it includes.
   For each example we list why it is invalid.
   
   . `MATCH (a) RETURN a.x + count(*)`
  
positive.code: ** Let `_PROJ_(_p_)` be `_ex_ AS _al_` and
  ** Let `_AGGR_(_p_)` be `_agg_(_al_) AS _al_`
  
  With this, `RETURN _p_~1~, _p_~2~, ... _p~N~_` can be defined as effectively equivalent to
  
  [source, cypher, subs="quotes"]
  ----
  
negative.code: . `MATCH (a) WITH a.x AS ax RETURN ax, ax + count(ax)`
  * The sub-expression `ax` is a grouping key.
  
  . `MATCH (a)-[]->(b) RETURN a, a.x + count(b.y)`
  * The sub-expression `a` is a grouping key.
  
  . `MATCH (a)-[]->(b) RETURN a, size(keys(a)) + count(b.y)`
  * The sub-expression `a` is a grouping key.
  
  . `MATCH (x) RETURN x.a, x.b, x.c, x.a + x.b + count(x) + x.c`
  * The sub-expressions `x.a`, `x.b`, and `x.c` are grouping keys.
  
  