PersistentOrderedSetIterator breaks if hash of an element changes #76
Description
Problem
Exception in thread "main" kotlin.KotlinNullPointerException
at kotlinx.collections.immutable.implementations.persistentOrderedSet.PersistentOrderedSetIterator.next(PersistentOrderedSetIterator.kt:22)
When iterating over a PersistentOrderedSet
How to reproduce
After creating the PersistentSet alter a contained element so its hash code changes.
import kotlinx.collections.immutable.PersistentSet
import kotlinx.collections.immutable.toPersistentSet
fun main() {
val changing = mutableSetOf("ok")
val persistent: PersistentSet<Any> = setOf("constant", changing, "fix").toPersistentSet()
doSomething(changing, persistent)
changing.add("break iteration")
doSomething(changing, persistent)
}
private fun doSomething(changing: MutableSet<String>, persistent: PersistentSet<Any>) {
println("actual hash is ${changing.hashCode()}")
val result = persistent.firstOrNull { it is Set<*> }
println("Found $result")
}
Version used: 0.3.2
Details
The error occurs in TrieNode.get(Int, K, Int) because although the data is in the buffer hasEntryAt() returns false. Seems like the dataMap is outdated.
Note: The set is not changed during iteration but during two independent iterations.
I found no documentation on PersistentSet that values must not change their hash codes. Like a Set it should always be iterable.
In my actual project I used a data class with a collection. A workaround is to use a normal class with the default hashCode() implementation.
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