Invalid UTestCyclicReferenceDescriptor

[IlyaMuravjov]

Add com.google.common.collect.TreeMultiset$AvlNode to UTBotJava/utbot-junit-contest/src/main/resources/classes/guava/list.

Run ContestEstimator with following settings:

timeLimit = 120
methodFilter = "com.google.common.collect.TreeMultiset\$AvlNode.deleteMe"
projectFilter = listOf("guava")

There's following error in logs:

23:55:01.029 | ERROR | JcToUtExecutionConverter.convert((id:19)com.google.common.collect.TreeMultiset$AvlNode#deleteMe()) failed
java.lang.IllegalStateException: Invalid UTestCyclicReferenceDescriptor: UTestCyclicReferenceDescriptor(refId=903229461, type=org.jacodb.impl.types.JcClassTypeImpl@105962b3)
	at org.utbot.contest.usvm.converter.JcToUtModelConverter.convertIgnoringOriginExprForThisModel(JcToUtModelConverter.kt:152) ~[main/:?]
	at org.utbot.contest.usvm.converter.JcToUtModelConverter.convert(JcToUtModelConverter.kt:72) ~[main/:?]
	at org.utbot.contest.usvm.converter.JcToUtModelConverter.convertIgnoringOriginExprForThisModel(JcToUtModelConverter.kt:106) ~[main/:?]
	at org.utbot.contest.usvm.converter.JcToUtModelConverter.convert(JcToUtModelConverter.kt:72) ~[main/:?]
	at org.utbot.contest.usvm.converter.JcToUtModelConverter.convertIgnoringOriginExprForThisModel(JcToUtModelConverter.kt:106) ~[main/:?]
	at org.utbot.contest.usvm.converter.JcToUtModelConverter.convert(JcToUtModelConverter.kt:72) ~[main/:?]
	at org.utbot.contest.usvm.converter.JcToUtExecutionConverter.convertState(JcToUtExecutionConverter.kt:224) ~[main/:?]
	at org.utbot.contest.usvm.converter.JcToUtExecutionConverter.convert(JcToUtExecutionConverter.kt:73) ~[main/:?]
	at org.utbot.contest.usvm.ContestUsvmKt$runUsvmGeneration$1$9$5.invoke(ContestUsvm.kt:190) [main/:?]
	at org.utbot.contest.usvm.ContestUsvmKt$runUsvmGeneration$1$9$5.invoke(ContestUsvm.kt:168) [main/:?]
	at org.utbot.contest.usvm.ContestUsvmKt$analyzeAsync$1$1$1.addState(ContestUsvm.kt:275) [main/:?]
	at org.utbot.contest.usvm.ContestUsvmKt$analyzeAsync$1$1$1.addState(ContestUsvm.kt:269) [main/:?]
	at org.usvm.statistics.collectors.CoveredNewStatesCollector.onStateTerminated(CoveredNewStatesCollector.kt:33) [usvm-core-local24-22-29.jar:?]
	at org.usvm.statistics.CompositeUMachineObserver.onStateTerminated(UMachineObserver.kt:48) [usvm-core-local24-22-29.jar:?]
	at org.usvm.UMachine.run(Machine.kt:66) [usvm-core-local24-22-29.jar:?]
	at org.usvm.machine.JcMachine.analyze(JcMachine.kt:195) [usvm-jvm-local24-22-29.jar:?]
	at org.utbot.contest.usvm.ContestUsvmKt$analyzeAsync$1.invoke(ContestUsvm.kt:267) [main/:?]
	at org.utbot.contest.usvm.ContestUsvmKt$analyzeAsync$1.invoke(ContestUsvm.kt:265) [main/:?]
	at org.utbot.common.ThreadBasedExecutor$invokeWithTimeout$1.invoke(ThreadUtil.kt:75) [utbot-core-2023.11-SNAPSHOT.jar:?]
	at org.utbot.common.ThreadBasedExecutor$ensureThreadIsAlive$1.invoke(ThreadUtil.kt:129) [utbot-core-2023.11-SNAPSHOT.jar:?]
	at org.utbot.common.ThreadBasedExecutor$ensureThreadIsAlive$1.invoke(ThreadUtil.kt:125) [utbot-core-2023.11-SNAPSHOT.jar:?]
	at kotlin.concurrent.ThreadsKt$thread$thread$1.run(Thread.kt:30) [kotlin-stdlib-1.8.22.jar:1.8.22-release-407(1.8.22)]

The issue is that in the instrumentation output there is UTestCyclicReferenceDescriptor with refId=903229461 in such place that no UTestObjectDescriptor containing it has refId=903229461.

Note, that is generally impossible in current abstractions to simultaneously always:

1. Have no cycles of UTestValueDescriptor
2. Only have UTestCyclicReferenceDescriptor in such places where there's UTestObjectDescriptor containing it and having same refId (here "containing" allows for indirect containing with intermediate layers, i.e. transitive closure of direct containment relationship)
3. Never use multiple UTestObjectDescriptors to describe same object in same state (initialState or finalState)

Consider the following example, where we want to build descriptor for result:

val x = X()
val y = Y()
y.x = x
x.y = y
val result = Result(x=x, y=y)

Here descriptors for result.y.x.y should be UTestCyclicReferenceDescriptor (to satisfy assumption 1) and descriptor for result.x.y should be UTestObjectDescriptor (to satisfy assumption 2), but they should be the same descriptor, i.e. descriptor in y field of descriptor for x, where x can only be described by only one instance of UTestObjectDescriptor (to satisfy assumption 3).

Further discussion is advised.

[IlyaMuravjov]

Fixed (dd5176f) by no longer relaying on assumption 2 when converting descriptors to UtModels. The question remains.