The issue was that when rendering declarations in
the `CONFLICTING_KLIB_SIGNATURES_DATA` diagnostics, we sort them using
`MemberComparator`. That comparator falls back to comparing
declarations' renders if all previous checks were unsuccessful
(and in case of almost identical properties they are). The renderer that
the comparator uses also renders the properties' backing field
annotations, for which it calls `PropertyDescriptor#getBackingField`.
That method wasn't implemented in IR-based descriptors.
This is fixed by returning an instance of the new
`IrBasedBackingFieldDescriptor` class from that method.
^KT-65551 Fixed
Sergej Jaskiewicz
d80a67652f