anchor-scope takes the following value:

none | all | <dashed-ident>#

If the value is a list of <dashed-ident>, it's not clear if the computed value serialization should preserve the order as in the original list.

For example, if the original value is:

anchor-scope: --a, --b, --c

is this an acceptable computed value serialization:

anchor-scope: --b, --a, --c