anchor.diff:  /// TODO: consider embedding hash code to make look-ups faster.
   type [<CustomEquality; NoComparison>] ArchetypeId =
       { ComponentNames : string HashSet
  -      Terms : Terms }
  +      Terms : Dictionary<string, Term> }
   
       static member inline Hash (hashSet : _ HashSet) =
           let mutable h = 0
  
positive.code:         end
  
  /// A collection of component stores.
  and 'w Archetype (storeTypes : Dictionary<string, Type>, terms : Terms) =
  
      let mutable freeIndex = 0
      let freeList = hashSetPlus<int> HashIdentity.Structural []
  
negative.code:             result
          else false
  
  type [<StructuralEquality; NoComparison>] Subquery =
      | Wildcard // matches everything
      | Eq of Term
  