anchor.diff:  format_error({nomatch_shadow,Line}) ->
       M = io_lib:format("this clause cannot match because a previous clause at line ~p "
   		      "always matches", [Line]),
  -    lists:flatten(M);
  +    flatten(M);
   format_error(nomatch_shadow) ->
       "this clause cannot match because a previous clause always matches";
   format_error(bad_call) ->
  
positive.code: 
  pattern_map_pairs(Ces0, Isub, Osub0, St0) ->
      %% pattern the pair keys and values as normal
      {Kes,{Osub1,St1}} = lists:mapfoldl(fun
  	    (#c_map_pair{anno=A,key=Ck,val=Cv},{Osubi0,Sti0}) ->
  		{Kk,[],Sti1} = expr(Ck, Isub, Sti0),
  		{Kv,Osubi2,Sti2} = pattern(Cv, Isub, Osubi0, Sti1),
  
negative.code: 		    {set_kanno(S, []),U,T,Fs}
  	    end;
  	#k_map{op=exact,es=Es} ->
              sort(fun(A,B) ->
  			%% on the form K :: {'lit' | 'var', term()}
  			%% lit < var as intended
  			erts_internal:cmp_term(A,B) < 0
  