anchor.diff:      %% Logger filters
       {error,{invalid_filter,_}} =
           logger:add_primary_filter(lf,{fun(_) -> ok end,args}),
  -    ok = logger:add_primary_filter(lf,{fun(_,_) -> a=b end,args}),
  +    ok = logger:add_primary_filter(lf,
  +                                   {fun(_,_) ->
  +                                            erlang:error({badmatch,b})
  +                                    end,
  +                                    args}),
       #{filters:=[_]} = logger:get_primary_config(),
       ok = logger:notice(M1=?map_rep),
       ok = check_logged(notice,M1,#{}),
  
positive.code:     {error,{not_found,h2}} = logger:remove_handler(h2),
  
      CallAddHandler = fun() -> logger:add_handler(h2,?MODULE,#{}) end,
      CrashHandler = fun() -> a = b end,
      KillHandler = fun() -> exit(self(), die) end,
  
      {error,{handler_not_added,{attempting_syncronous_call_to_self,_}}} =
  
negative.code:     false = lists:search(fun(#{id:=h1}) -> true; (_) -> false end,H1),
      {error,{not_found,h1}} = logger:remove_handler(h1),
  
      ok = logger:add_handler(h2,?MODULE,
                              #{filter_default => log,
                                log_call => fun() ->
                                                    erlang:error({badmatch,b})
                                            end}),
      {error,{already_exist,h2}} = logger:add_handler(h2,othermodule,#{}),
      [add] = test_server:messages_get(),
  
  