Description
If you investigate the documentable model for a class with a companion object, DClass.companion and DClass.classlikes.single() are different by reference. They represent the same object, and have the the same values in every field, recursively.
However, they are also different by value, because .equals() on the data class DClass recurses into DClass.sources.values.single().descriptor.equals(), which is (in K1) a non-data-class org.jetbrains.kotlin.resolve.lazy.descriptors.LazyClassDescriptor which compares by reference instead of by value. I would guess that the K2 implementation of DocumentableSource similarly recurses into a problematic upstream object.
a) Please make sure that only one DObject is created for each companion object. Not only should this (slightly) help performance, it will help avoid running into issues like this when trying to check if a companion object is contained within a list of objects.
b) Please make Documentables compare by value correctly. Avoiding sources entirely in an overridden .equals()/.hashCode would maintain correctness IMO, but making the upstream objects inside all implementations of DocumentableSources compare by value would probably be more correct, though skipping them in .equals()/.hashCode implementations probably can be made correct.