public abstract fun withNullability(type: KaType, newNullability: KaTypeNullability): KaType

    public abstract fun haveCommonSubtype(a: KaType, b: KaType): Boolean

    public abstract fun getImplicitReceiverTypesAtPosition(position: KtElement): List<KaType>

        require(type is KaFirType)
        return type.coneType.withNullability(newNullability.toConeNullability(), rootModuleSession.typeContext).asKtType()
    }

    override fun haveCommonSubtype(a: KaType, b: KaType): Boolean {
        return analysisSession.useSiteSession.typeContext.isCompatible(
            a.coneType,
            b.coneType
        ) == ConeTypeCompatibilityChecker.Compatibility.COMPATIBLE

        require(type is KaFe10Type)
        return type.fe10Type.makeNullableAsSpecified(newNullability == KaTypeNullability.NULLABLE).toKtType(analysisContext)
    }

    override fun haveCommonSubtype(a: KaType, b: KaType): Boolean {
        return areTypesCompatible((a as KaFe10Type).fe10Type, (b as KaFe10Type).fe10Type)
    }

    override fun getImplicitReceiverTypesAtPosition(position: KtElement): List<KaType> {