Collect variables from several resources into one variable?

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Consider a module that declares the class module::singleton and defines the type module::many. Is there any way for the class to see the names of the defined types? Here's an example:

class module::singleton {
  $foo = declared_names_of_type(module::many)   //This doesn't work. Can it even be done?
}

define type module::many { }

include module::singleton
module::many {'first':}
module::many {'second':}

To be more specific, I'm working on a module for SSSD. The config file for SSSD requires that each domain is named at the top, and also has its own config stanza down below. It looks ... (more)