anchor.diff:                       {ok, Parse4};
                    {error, unknown} ->
                        error({invalid_syntax, SyntaxOp});
  +                 {error, syntax} when SkipInvalid ->
  +                     {ok, Parse};
                    {error, syntax} ->
                        {error, syntax_error(Key2, Parse)};
                    {error, Error} ->
  
positive.code:         _ ->
              maps:get(allow_unknown, Opts, false)
      end,
      Parse = #parse{
          syntax = Syntax,
          opts = Opts,
          path = maps:get(path, Opts, <<>>),
          allow_unknown = AllowUnknown
      },
      case do_parse(Terms, Parse) of
          {ok, #parse{ok=Ok, no_ok=NoOk}} ->
  
negative.code:     syntax :: map(),
      path :: binary(),
      allow_unknown :: boolean(),
      skip_invalid :: boolean(),
      opts :: parse_opts()
  }).
  
  