Do not treat members with already changed signature as a reason
to create a hidden copy
See tests for clarification:
- There are `charAt` method in B that has different name in Kotlin - `get`,
i.e. relevant descriptor has initialSignatureDescriptor != null
- When collecting methods from supertypes, `charAt` from A is also get
transformed to `get`
- So it has effectively the same signature as B.get (already declared)
- If by an accident B.get had been declared with Kotlin signature
we would have add A.charAt (after transformation) with special flag:
HiddenToOvercomeSignatureClash (hides it from resolution)
- But here B.charAt was artificially changed to `get`, so no signature clash
actually happened
#KT-13730 Fixed
