The change in
`FirOptInUsageBaseChecker` is needed
to prevent `OPT_IN_OVERRIDE` on
intersection overrides where one
of the base functions requires opt-in.
We never designed this in such
a way that it's an error.
See:
`FirPsiOldFrontendDiagnosticsTestGenerated.testIncorrectTargetsForExperimentalAnnotation`.
According to KT-63741, the case like
`kt40510.fir.kt` should, in fact,
be an error. It will be addressed
separately.
Nikolay Lunyak
694029d67f