How to use validation.ListOfUniqueStrings

I’m writing a custom provider and I’m trying to enforce both uniqueness and order on a list of strings in one of my resources. I wanted to use validation.ListOfUniqueStrings but when I try to run my acceptance tests, I get an error stating: ValidateFunc and ValidateDiagFunc are not yet supported on lists or sets.

So how exactly do I use this validation function? It seems to have been around for quite a while, but I can’t find any examples of it actually being used anywhere.