anchor.diff:  %%% 
   
   -import(lists, [reverse/1,reverse/2,foldl/3]).
  +
  +-type instruction() :: beam_utils:instruction().
  +
  +-spec module(beam_utils:module_code(), [compile:option()]) ->
  +                    {'ok',beam_utils:module_code()}.
   
   module({Mod,Exp,Attr,Fs0,Lc}, _Opt) ->
       Fs = [function(F) || F <- Fs0],
  
positive.code: %%  Test whether the instruction Instruction always
  %%  causes an exit/failure.
  
  is_exit_instruction({call_ext,_,{extfunc,M,F,A}}) ->
      erl_bifs:is_exit_bif(M, F, A);
  is_exit_instruction(if_end) -> true;
  
negative.code: %% is_unreachable_after(Instruction) -> boolean()
  %%  Test whether the code after Instruction is unreachable.
  
  -spec is_unreachable_after(instruction()) -> boolean().
  
  is_unreachable_after({func_info,_M,_F,_A}) -> true;
  is_unreachable_after(return) -> true;
  is_unreachable_after({jump,_Lbl}) -> true;
  