I think that kind of assignation ('user.id','=',3) does not logically make sense, as the left side argument is normally a field or property that comes from the model, and the right side argument is the value you want to compare it to.

For example, if the model had a field, user_id, then you could use:

('user_id','=',3) or ('user_id','=',user.id) 

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I don't know if this is a correct example, but your current record rule would be like trying to write a SQL query like:

select * from res_partner where 3=user_id

instead of:

select * from res_partner where user_id=3;