Everything you need to know about Kotlin 2.0

Took from Kotlin

In this article, we will dive into some of the most exciting features and changes that Kotlin 2.0 offers. Whether you’re a seasoned Kotlin developer or just starting, these updates will improve your coding experience.

Frontend Immediate Representation

One of the significant enhancements in Kotlin 2.0 is the improved handling of operators, especially when dealing with different numeric types like Long and Int. In previous versions, using the += operator with mismatched types could cause errors. For instance:

fun increment(list: MutableList<Long>) {
    list[0] += 1 // Error in Kotlin 1.x because 1L is required
}

In Kotlin 2.0, this issue is resolved, making the code more intuitive and less error-prone:

fun increment(list: MutableList<Long>) {
    list[0] += 1 // No Error in Kotlin 2.0
}

The Nullable Left side can’t use operator assignments event with the correct type due to nullability in 1.x but it works correctly with Kotlin 2.0

data class Section(
    val students: MutableList<Long> = mutableListOf(),
)
fun incrememnt(section:Section?){
     section?.students[0] += 1L // Error In 1.x but OK in 2.x  
}

// In Kotlin 2.0
// Desugared Code :
// section.run{section?.run{students.set(0,students.get(0).plus(1) ) }

This enhancement simplifies the code and eliminates the need for explicit type conversions in many scenarios.

Enhanced Smart Casts

Kotlin has always been known for its smart casting capabilities, but Kotlin 2.0 takes it a step further. In Kotlin 1.x, smart casting didn’t carry over through variables. For example:

class Dog {
    fun bark() {
        println("bark")
    }
}

fun petAnimal(animal: Any) {
    val isDog = animal is Dog
    if (isDog) {
        // Error: animal is not cast to Dog
        animal.bark()
    }
}

With Kotlin 2.0, the smart cast works seamlessly, recognizing animal as Dog within the if block:

fun petAnimal(animal: Any) {
    if (animal is Dog) {
        animal.bark() // No error, animal is recognized as Dog
    }
}