*
     * Example: `foo.bar.Baz.Inner` with 1 dropped class is `foo.bar.Baz`, and with 2 dropped class is `null`.
     */
    private fun ClassId.dropLastNestedClasses(classesToDrop: Int) =
        generateSequence(this) { it.outerClassId }.drop(classesToDrop).firstOrNull()

    /**
     * @return How many qualifiers needs to be dropped from [wholeType] to get [nestedType].
     *