I am wondering what was the intent of this test case added by commit
257836a75:
CREATE INDEX icuidx16_mood ON collate_test(id) WHERE mood > 'ok' COLLATE "fr-x-icu";
where "mood" is of an enum type, which surely does not respond to
collations.
The reason I ask is that this case started failing after I fixed
a parse_coerce.c bug that allowed a CollateExpr node to survive
in this WHERE expression, which by rights it should not. I'm
inclined to think that the test case is wrong and should be removed,
but maybe there's some reason to have a variant of it.
regards, tom lane