[GENERAL] 9.5 "chained equality" behavior

 ?column?

----------

 t

(1 row)

ERROR:  syntax error at or near "="

LINE 1: SELECT true = true = true;

Now, there's actually a larger problem with this, since it's not actually chained equality and only looks like it. It looks like 9.4 is evaluating right-to-left. We're going to fix usages of this to instead do (a = b && a = c) instead of (a = b = c).

However, I wanted to email in because I couldn't see what in the 9.5 changelog (https://www.postgresql.org/docs/9.6/static/release-9-5.html) would cause this to syntax error. I'm worried that there are other incompatibilities that we didn't notice.

Can anyone shed some light?