Add details to the UNLESS CONFLICT ELSE message about parents
@@ -482,6 +482,9 @@ def compile_insert_unless_conflict_on(
raise errors.UnsupportedFeatureError(
'UNLESS CONFLICT can not use ELSE when constraint is from a '
'parent type',
+ details=(
+ f"The existing object can't be exposed in the ELSE clause "
+ f"because it may not have type {typ.get_name(schema)}"),
context=constraint_spec.context,
)
