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.