ERROR: wrong varnullingrels (b 3) (expected (b)) for Var 2/1

[Markus Winand]

I found an error similar to others before ([1]) that is still persists as of 
head right now (0bcb3ca3b9).

CREATE TABLE t (
        n INTEGER
);

SELECT *
  FROM (VALUES (1)) t(c)
  LEFT JOIN t ljl1 ON true
  LEFT JOIN LATERAL (WITH cte AS (SELECT * FROM t WHERE t.n = ljl1.n) SELECT * 
FROM cte) ljl2 ON ljl1.n = 1;

ERROR:  wrong varnullingrels (b 3) (expected (b)) for Var 2/1

Note that the error does **not** occur if the CTE is unwrapped like this:

SELECT *
  FROM (VALUES (1)) t(c)
  LEFT JOIN t ljl1 ON true
  LEFT JOIN LATERAL (SELECT * FROM t WHERE t.n = ljl1.n) ljl2 ON ljl1.n = 1;

-markus

[1] 
https://www.postgresql.org/message-id/CAHewXNnu7u1aT==wjncra+szkb6s80hvwpp_9emvvvtdyfd...@mail.gmail.com