Vacuous test in LongMap likely results in incorrect behavior

[Ichoran]

Reproduction steps

Standard library bug. Example in Scala 3 REPL:

scala> val lm = collection.mutable.LongMap.empty[String]
val lm: scala.collection.mutable.LongMap[String] = LongMap()

scala> val minA = lm.put(Long.MinValue, "eel")
val minA: Option[String] = None
                                                                                
scala> val minB = lm.put(Long.MinValue, "cod")
val minB: Option[String] = None

Problem

An apparently LLM-generated PR noticed that line 294 in collection.mutable.LongMap contains a vacuous test:

val ans = if ((extraKeys&2) == 1) Some(minValue.asInstanceOf[V]) else None

Because of this, when LongMap has a pre-existing Long.MinValue key, indicated by bit 0x2 set in extraKeys, it incorrectly finds nothing and returns None. The map remains correct; the only problem is that the stored value is lost rather than being returned by put as its contract requires.

The LLM correctly guessed that it was meant to be == 2, but did not test the fix or submit a test. I also do not have time right now to do this, but I understand the context and that there is genuinely incorrect behavior.