anchor.diff:  format_field_skippers(MsgName, AnRes) ->
       SkipVarintFnName = mk_fn(skip_varint_, MsgName),
       SkipLenDelimFnName = mk_fn(skip_length_delimited_, MsgName),
  -    ReadFieldFnName = mk_fn(d_read_field_def_, MsgName),
  +    ReadFieldFnName = mk_fn(dfp_read_field_def_, MsgName),
       Params = decoder_params(MsgName, AnRes),
       [%% skip_varint_<MsgName>/2,4
        gpb_codegen:format_fn(
  
positive.code:         splice_trees('<InParams>', Params),
          replace_term(decode_packed, mk_fn(d_packed_field_, MsgName, FName)),
          replace_tree('<Param>', Param),
          replace_term('<call-read-field>', mk_fn(d_read_field_def_, MsgName)),
          splice_trees('<OutParams>', OutParams)]),
       "\n",
       format_packed_field_seq_decoder(MsgName, FieldDef, Opts)].
  
negative.code:     InParams = decoder_in_params(Params, MsgName, FieldDef, AnRes),
      BodyTailFn =
          fun(DecodeExprs, Rest2Var) ->
                  ReadFieldDefFn = mk_fn(dfp_read_field_def_, MsgName),
                  Params2 = updated_merged_params(MsgName, FieldDef, AnRes,
                                                  FVar, Params),
                  C = ?exprs('<call-read-field>'('<Rest2>', 0, 0, '<Params2>'),
  