t5589neg2.scala:7: error: constructor cannot be instantiated to expected type;
 found   : (T1, T2)
 required: String
    for (((((a, (b, (c, (d1, d2)))), es), fs), gs) <- x) yield (d :: es).mkString(", ") // not ok
                        ^
t5589neg2.scala:7: error: not found: value d
    for (((((a, (b, (c, (d1, d2)))), es), fs), gs) <- x) yield (d :: es).mkString(", ") // not ok
                                                                ^
two errors found