How to combine "in" and "case"?

Question

SQL Server

I can write such a predicate in where

select *
from customer
inner join documents on documents.customer_id = customer_id
where customer.type = case ... end

It doesn't work that way with the "in" construct, what other way can it be done?
It is necessary that, depending on the type of user, different groups of documents are returned

select *
from customer
inner join documents on documents.customer_id = customer_id
where documents.id in case when customer.type = 'A' then (1,2,3) when customer.type = 'B' then (3,5,6) end

I should end up with something like this:

customer1 - customer_typeA - document1
customer1 - customer_typeA - document2
customer1 - customer_typeA - document3

customer2 - customer_typeB - document3
customer2 - customer_typeB - document5
customer2 - customer_typeB - document6

Answer 1

in implies a
case list - implies a single value , of
course you can pervert and do something like ... in (case...end)but why?