anchor.diff:  -record(constraint_list, {type :: 'conj' | 'disj',
   			  list :: [constr()],
                             deps :: deps(),
  -                          masks = maps:new() :: #{dep() => mask()},
  +                          masks ::  #{dep() => mask()} | 'undefined',
   			  id   :: {'list', dep()} | 'undefined'}).
   
   -type constraint_list() :: #constraint_list{}.
  
positive.code: 
  update_masks(C, Masks) ->
    C#constraint_list{masks = Masks}.
  
  calculate_masks([C|Cs], I, L0) ->
    calculate_masks(Cs, I+1, [{V, I} || V <- get_deps(C)] ++ L0);
  
negative.code:               M <- lists:usort([M || {M, _, _} <- SCC])],
    State2 = traverse_scc(SCC, CServer, DefSet, ModRecs, State1),
    State3 = state__finalize(State2),
    Funs = state__scc(State3),
    pp_constrs_scc(Funs, State3),
    constraints_to_dot_scc(Funs, State3),
  