Something wrong with repeated in option

[DoneSpeak]

syntax = "proto2";

option java_multiple_files = true;

import "google/protobuf/descriptor.proto";

package testoption;

extend google.protobuf.FieldOptions {
    optional Fields rules = 1000000;
    optional InValues values = 2000000;
}

message Fields {
    oneof rules {
        InValues values = 1;
    }
}

message InValues {
    repeated int32 in = 1;
    repeated int32 not_in = 2;
}

message TestValues {
    repeated int32 vals = 1 [(testoption.rules).values = {in: [1,2,3]}];
    repeated int32 vals2 = 2 [(testoption.values) = {in: [1,2,3]}];
}

I was told that Couldn't resolve reference to IndexedElement 'in' when I created this proto file. But actually, It works as it was expected. So I think that is it a problem of protocol-dt?