Can an extension function defined inside a class in Kotlin access its fields and methods?

Extension functions in Kotlin are not true class methods; they are compiled into static functions that take an object as a parameter. Therefore, they do not have direct access to the class's private fields and methods.

However, if an extension function is defined inside a class, it can access the members of that class, but not the private members of the object to which the extension is applied.

Example:

class MyClass {
    private val secret = "secret"

    fun String.extensionFunction() {
        println(this) // access to String
        // println(secret) // Error: no access to private field of String object
    }

    fun test() {
        "Hello".extensionFunction() // call to extension function
    }
}

Thus, an extension function inside a class can access the members of the class in which it is declared, but not the private fields and methods of the object to which the extension is applied.