+ factoryGetter()
+ buildFactoryGetter()
    private void genTypedConcatMethod() {        String formalSepArgs = buildFormalSeparatorArguments(listType);        String actualSepArgs = buildActualSeparatorArguments(listType);        String typeName = getTypeName();        println(            "  public " + typeName + " concat(" + formalSepArgs + typeName + " peer) {");        println(            "    return "                + factoryGetter()                + ".concat(this, "                + actualSepArgs                + "peer);");        println("  }");        println();    }