Use case
SELECT 1 IN (SELECT -1)

This task it not trivial as it looks.

We can apply conversion for left hand side to the type of right hand side.
But this will lead to strange artifacts: SELECT 257 IN (SELECT 1) will return true.

We can apply conversion to the lest common type, but we create the set only one time but may use it in different context, e.g:
SELECT 1 IN (SELECT 18446744073709551615), -1 IN (SELECT 18446744073709551615)