anonymous template predicates

[Vlad Levenfeld via Digitalmars-d-learn]

I was wondering if there's a mechanism to make anonymous 
templates, e.g.

given:
   enum Policy {A, B}
   alias List = TypeTuple!(...);

instead of this:

   enum has_policy_A (T) = T.policy == Policy.A;
   alias Result = Filter!(has_policy_A, List);

use something like this:

   Filter!(T => T.policy == Policy.A, List);

I've tried templates that generate eponymous predicates from 
mixed-in strings but these have a number of caveats that limit 
their usability.