Shrinking goes into semi-infinite recursion

Here is a commit, for which IteratorExtensionSpec never ends after entering Prop.findFirstFailure: sugar.

This happens fairly often for me; here is another one

Stacktrace:

  java.lang.Thread.State: RUNNABLE
	at scala.collection.Iterator.sameElements(Iterator.scala:843)
	at scala.collection.Iterator.sameElements$(Iterator.scala:840)
	at scala.collection.AbstractIterator.sameElements(Iterator.scala:1300)
	at net.noresttherein.sugar.collections.IteratorExtensionSpec$.prop$2(IteratorExtensionSpec.scala:38)
	at net.noresttherein.sugar.collections.IteratorExtensionSpec$.$anonfun$mappingProperty$10(IteratorExtensionSpec.scala:45)
	at net.noresttherein.sugar.collections.IteratorExtensionSpec$$$Lambda$117/0x0000000801124e38.apply(Unknown Source)
	at scala.Function1.$anonfun$andThen$1(Function1.scala:87)
	at scala.Function1$$Lambda$80/0x000000080110d388.apply(Unknown Source)
	at org.scalacheck.Prop$.$anonfun$forAllShrink$2(Prop.scala:769)
	at org.scalacheck.Prop$$$Lambda$95/0x0000000801114d98.apply(Unknown Source)
	at org.scalacheck.Prop$.secure(Prop.scala:479)
	at org.scalacheck.Prop$.result$1(Prop.scala:769)
	at org.scalacheck.Prop$.$anonfun$forAllShrink$4(Prop.scala:778)
	at org.scalacheck.Prop$$$Lambda$234/0x000000080114ca58.apply(Unknown Source)
	at scala.collection.immutable.Stream.map(Stream.scala:173)
	at org.scalacheck.Prop$.getFirstFailure$1(Prop.scala:778)
	at org.scalacheck.Prop$.shrinker$1(Prop.scala:792)
	at org.scalacheck.Prop$.$anonfun$forAllShrink$1(Prop.scala:813)
	at org.scalacheck.Prop$$$Lambda$81/0x000000080110d740.apply(Unknown Source)
	at org.scalacheck.Prop$.$anonfun$apply$1(Prop.scala:309)
	at org.scalacheck.Prop$$$Lambda$17/0x000000080102a7a0.apply(Unknown Source)
	at org.scalacheck.PropFromFun.apply(Prop.scala:22)
	at org.scalacheck.Prop.$anonfun$map$1(Prop.scala:52)
	at org.scalacheck.Prop$$Lambda$106/0x000000080111ceb8.apply(Unknown Source)
	at org.scalacheck.Prop$.$anonfun$apply$1(Prop.scala:309)
	at org.scalacheck.Prop$$$Lambda$17/0x000000080102a7a0.apply(Unknown Source)
	at org.scalacheck.PropFromFun.apply(Prop.scala:22)
	at org.scalacheck.Prop.$anonfun$flatMap$1(Prop.scala:58)
	at org.scalacheck.Prop$$Lambda$85/0x000000080110e6e8.apply(Unknown Source)
	at org.scalacheck.Prop$.$anonfun$apply$1(Prop.scala:309)
	at org.scalacheck.Prop$$$Lambda$17/0x000000080102a7a0.apply(Unknown Source)
	at org.scalacheck.PropFromFun.apply(Prop.scala:22)
	at org.scalacheck.Prop.$anonfun$flatMap$1(Prop.scala:56)
	at org.scalacheck.Prop$$Lambda$85/0x000000080110e6e8.apply(Unknown Source)
	at org.scalacheck.Prop$.$anonfun$apply$1(Prop.scala:309)
	at org.scalacheck.Prop$$$Lambda$17/0x000000080102a7a0.apply(Unknown Source)
	at org.scalacheck.PropFromFun.apply(Prop.scala:22)
	at org.scalacheck.Prop$.$anonfun$delay$1(Prop.scala:484)
	at org.scalacheck.Prop$$$Lambda$16/0x000000080102a3e8.apply(Unknown Source)
	at org.scalacheck.Prop$.$anonfun$apply$1(Prop.scala:309)
	at org.scalacheck.Prop$$$Lambda$17/0x000000080102a7a0.apply(Unknown Source)
	at org.scalacheck.PropFromFun.apply(Prop.scala:22)
	at org.scalacheck.Prop.$anonfun$viewSeed$1(Prop.scala:41)
	at org.scalacheck.Prop$$Lambda$18/0x000000080102ab58.apply(Unknown Source)
	at org.scalacheck.Prop$.$anonfun$apply$1(Prop.scala:309)
	at org.scalacheck.Prop$$$Lambda$17/0x000000080102a7a0.apply(Unknown Source)
	at org.scalacheck.PropFromFun.apply(Prop.scala:22)
	at org.scalacheck.Test$.workerFun$1(Test.scala:474)
	at org.scalacheck.Test$.$anonfun$check$4(Test.scala:506)
	at org.scalacheck.Test$.$anonfun$check$4$adapted(Test.scala:506)
	at org.scalacheck.Test$$$Lambda$29/0x00000008010c27b0.apply(Unknown Source)
	at org.scalacheck.Platform$.runWorkers(Platform.scala:40)
	at org.scalacheck.Test$.check(Test.scala:506)
	at org.scalacheck.Test$.$anonfun$checkProperties$2(Test.scala:547)
	at org.scalacheck.Test$$$Lambda$28/0x00000008010c6d08.apply(Unknown Source)
	at scala.collection.StrictOptimizedIterableOps.map(StrictOptimizedIterableOps.scala:100)
	at scala.collection.StrictOptimizedIterableOps.map$(StrictOptimizedIterableOps.scala:87)
	at scala.collection.mutable.ListBuffer.map(ListBuffer.scala:39)
	at org.scalacheck.Test$.checkProperties(Test.scala:538)
	at org.scalacheck.Properties.main(Properties.scala:77)
	at net.noresttherein.sugar.collections.IteratorExtensionSpec.main(IteratorExtensionSpec.scala)

Start by reproducing the hang with test/scala/net/noresttherein/sugar/collections/IteratorExtensionSpec.scala and the linked scalacheck_bug commit, focusing on the call into Prop.findFirstFailure. Compare it with the second linked commit and use the stack trace to trace the shrinking path. Done means the property check terminates instead of entering semi-infinite recursion.