Section 2.0.30.3 states the following rule about ids and type choices:

For type choice elements, the id reflects the type slice. e.g. For path = Patient.deceasedBoolean, the id is Patient.deceased[x]:deceasedBoolean

Based on this, it seems that the slice name must be the explicit type choice (e.g., deceasedBoolean). What happens if a type choice element is a list (e.g., max: '*') and you want to further slice that element?

For example, imagine Foo with 0..* value[x] where it is a choice of Coding or string. The id of the Coding would be Foo.value[x]:Coding. Now imagine we want to further slice the Coding to specify that one Coding should be fixed to a value (but allow other Codings as well). Would that just be a re-slicing (e.g., that fixed slice would have id: Foo.value[x]:Coding/MyFixedSlice)?

This may be a hypothetical, given that I can't think off-hand of any resource that has a type choice element that has a max > 1.