Outer query reference is not resolved inside a nested set-operation operand

Description

MariaDB Server 12.3.2 cannot resolve an outer query's table alias in a correlated SELECT inside a parenthesized INTERSECT operand of UNION. The outer alias is visible to an equivalent flat UNION branch and to a non-nested INTERSECT.

This report concerns a correlated SELECT in WHERE EXISTS. The reproduction does not place an outer reference inside a FROM-derived table that would require LATERAL.

How to repeat

SELECT o.a

FROM (SELECT 1 AS a UNION ALL SELECT 2) AS o

WHERE EXISTS (

    SELECT 0 WHERE FALSE

    UNION

    (SELECT 1 WHERE o.a = 1 INTERSECT SELECT 1)

);

Actual result

ERROR 1109 (42S02): Unknown table 'o' in WHERE