BUG #19777: PERIOD foreign key rejects an empty referencing range even though the referenced period covers it

The following bug has been logged on the website:

Bug reference: 19777
Logged by: N J
Email address: 1482694023(at)qq(dot)com
PostgreSQL version: 18.6
Operating system: Windows 11 x64
Description:

Tested with PostgreSQL 18.6 on Windows 11 x64. No extensions or non-default
configuration are required.

On a fresh connection, run the setup and check:

CREATE TEMP TABLE period_parent_minimal (
k int4range NOT NULL,
p int4range NOT NULL,
PRIMARY KEY (k, p WITHOUT OVERLAPS)
);

INSERT INTO period_parent_minimal
VALUES ('[1,2)'::int4range, '[0,10)'::int4range);

CREATE TEMP TABLE period_child_minimal (
k int4range NOT NULL,
p int4range NOT NULL,
FOREIGN KEY (k, PERIOD p)
REFERENCES period_parent_minimal (k, PERIOD p)
);

SELECT range_agg(p) @> 'empty'::int4range AS parent_covers_empty
FROM period_parent_minimal
WHERE k = '[1,2)'::int4range;

The SELECT returns true. Then run:

INSERT INTO period_child_minimal
VALUES ('[1,2)'::int4range, 'empty'::int4range);

Actual result: rejected with SQLSTATE 23503 (foreign key violation).

Expected result: the insert should succeed if an empty referencing period is
considered covered by the referenced period, consistent with range
containment and the documented PERIOD foreign-key coverage rule. Please
confirm whether empty referencing periods are intended to satisfy PERIOD
foreign keys.