anchor.diff:          field08 => host,
           field09 => host6,
           field10 => fun parse_fun/3,
  -        field11 => [{atoms, [a]}, binary],
  +        field11 => [{atom, [a]}, binary],
           field12 => {list, atom},
           field13 => module,
           fieldXX => invalid
  
positive.code:         error -> error
      end;
  
  spec({atoms, List}, Val) ->
      case to_existing_atom(Val) of
          {ok, Atom} ->
              case lists:member(Atom, List) of
  
negative.code:     Spec = #{
          field01 => atom,
          field02 => boolean,
          field03 => {atom, [a, b]},
          field04 => integer,
          field05 => {integer, 1, 5},
          field06 => string,
  