INSERT w/ ON CONFLICT DO NOTHING RETURNING * is returning rows for ignored conflicts

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Describe the bug

In Postgres, when you combine ON CONFLICT DO NOTHING with RETURNING, the conflicting rows are not returned.

To Reproduce

CREATE TABLE example (id bigint PRIMARY KEY);
INSERT INTO example (id) VALUES (1) RETURNING *;
-- id: 1
INSERT INTO example (id) VALUES (1) ON CONFLICT DO NOTHING RETURNING *;
-- id: 1 (WRONG)

pg-mem version

2.6.13