anchor.diff:  %% UNUSED VARS
   
   check_unused_vars(#{unused_vars := Unused} = E) ->
  -  [elixir_errors:form_warn([{line, Line}], ?key(E, file), ?MODULE, {unused_var, Name, false}) ||
  +  [elixir_errors:form_warn([{line, Line}], ?key(E, file), ?MODULE, {unused_var, Name}) ||
       {{{Name, _}, _}, Line} <- maps:to_list(Unused), Line /= false, not_underscored(Name)],
     E.
   
  
positive.code: 
            %% Otherwise we must warn
            _ ->
              {{Name, _} = Pair, _} = Key,
  
              case not_underscored(Name) of
                true ->
                  IsShadowing = maps:is_key(Pair, ?key(E, current_vars)),
                  Warn = {unused_var, Name, IsShadowing},
                  elixir_errors:form_warn([{line, ClauseValue}], ?key(E, file), ?MODULE, Warn);
  
                false ->
  
negative.code:     _ -> true
    end.
  
  format_error({unused_var, Name}) ->
    io_lib:format("variable \"~ts\" is unused (if the variable is not meant to be used, prefix it with an underscore)", [Name]).
  