equal: don't know whether nodes of type 600 are equal

regression=> SELECT 1 AS two UNION SELECT 2;
NOTICE: equal: don't know whether nodes of type 600 are equal
two
---
1
2
(2 rows)

gdb:

#0 equal (a=0x179f10, b=0x1c1490) at equalfuncs.c:746
#1 0x7bf4d in remove_duplicates (list=0x167d90) at prepqual.c:563
#2 0x7b86a in qual_cleanup (qual=0x168f50) at prepqual.c:234
#3 0x7b48e in cnfify (qual=0x168790, removeAndFlag=1 '\001') at prepqual.c:76
#4 0xba22a in Except_Intersect_Rewrite (parsetree=0x179f10)
^^^^^^^^^^^^^^^^^^^^^^^^
at rewriteHandler.c:2842

Vadim