anchor.diff:  . `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.
   
  
positive.code: 
  The proposal tries to strike a balance between allowing good number of useful queries while keeping the rules of the syntax restrict reasonable simple.
  
  Also note: For queries that are logically possible but rejected by the syntax restriction, users can always manually rewrite the query with additional explicit projections to make the query syntactically valid while it still produces the desired result.
negative.code: 
  The RETURN clause
  
  .[[Q7]]Q7
  [source, cypher]
  ----
  RETURN a AS a, (b - b) + SUM(c) AS foo
  