MaxTotal does not take idle resources into account

scala> val p = IO.ref(0).flatMap(ref =>
     |   KeyPool.Builder((i: Int) => Resource.make(ref.update(_ + 1).as(i))(i => IO.println(s"kill $i") *> ref.update(_ - 1)))
     |     .withMaxTotal(5)
     |     .withMaxIdle(5)
     |     .build.use{ keypool =>
     |       keypool.take(0).replicateA(5).use(_ => ref.get.flatMap(i => IO.println(s"total $i"))) *>
     |       keypool.take(1).replicateA(5).use(_ => ref.get.flatMap(i => IO.println(s"total $i"))) *>
     |       IO.println("DONE") *>
     |       ref.get
     |     }
     | )
val p: cats.effect.IO[Int] = IO(...)

scala> p.unsafeRunSync()
total 5
total 10
kill 1
kill 1
kill 1
kill 1
DONE
kill 0
kill 0
kill 0
kill 0
kill 0
kill 1
val res29: Int = 6

As you can see, at one point 10 resources are allocated, while the max is set to 5. At the end there are still 6 which might be a separate issue...

Start by reproducing the Scala example and tracing KeyPool.Builder, withMaxTotal, and withMaxIdle to find how idle resources are counted. Confirm the fix by rerunning the example and verifying that allocation never exceeds the configured maximum; the final resource count may be a separate issue.