---
title: "Kotlin 2.0 — Key Syntax Changes"
url: "https://romankryvolapov.com/en/kotlin-2-key-syntax-changes/"
description: "What changed in Kotlin 2.0 syntax: context receivers, value classes, sealed interfaces, destructuring in for loops and pattern matching in when."
language: en
updated: 2026-01-21
---
In this article I will describe the main innovations in the syntax compared to previous versions.

The full list of new features can be found here:

[https://kotlinlang.org/docs/whatsnew20.html](https://kotlinlang.org/docs/whatsnew20.html)

## Context Receivers {#Context-Receivers}

```kotlin
// Kotlin 1.x:

class User(
  val name: String
)

fun greet(user: User) {
  with(user) {
    println("Hello, $name")
  }
}

fun main() {
  greet(User("Alice"))
}

// Kotlin 2.0:
// Now you can add contexts for functions,
// to explicitly specify their dependencies at the API level:

class User(
  val name: String
)

context(User)

fun greet() {
  println("Hello, $name")
}

fun main() {
  val user = User("Alice")
  with(user) {
    greet()
  }
}
```

## Value classes (renamed inline classes) {#Value-classes-renamed-inline-classes}

They work similarly, but the new name better reflects their essence, and also provides additional optimizations when using such classes on the JVM.

```kotlin
// Kotlin 1.x:

inline class Name(
  val value: String
)


// Kotlin 2.0:

@JvmInline
value class Name(
  val value: String
)
```

## Sealed Interface {#Sealed-Interface}

```kotlin
// Kotlin 1.x:

sealed class Shape {

  class Circle(
    val radius: Double
  ) : Shape()

  class Square(
    val side: Double
  ) : Shape()

}

// Kotlin 2.0:
// now you can make sealed interfaces

sealed interface Shape

class Circle(
  val radius: Double
) : Shape

class Square(
  val side: Double
) : Shape
```

## Labels for lambdas and anonymous functions {#Labels-for-lambdas-and-anonymous-functions}

```kotlin
fun process(
  action: () -> Unit
) {
  action()
}

fun main() {
  process {
    return@process println("Lambda with label")
  }
}
```

## Support for new collection operations {#Support-for-new-collection-operations}

```kotlin
val list = listOf(1, 2, 3)

val doubled = list.mapNotNull {
  if (it > 1) it * 2
  else null
}
```

## Support for new syntax for pattern matching in when {#Support-for-new-syntax-for-pattern-matching-in-when}

```kotlin
sealed class Shape

class Circle(
  val radius: Double
) : Shape()

class Square(
  val side: Double
) : Shape()

fun describeShape(shape: Shape): String = when (shape) {
  is Circle -> "Circle with radius ${shape.radius}"
  is Square -> "Square with side ${shape.side}"
}
```

## Multi-declarations for classes with operator {#Multi-declarations-for-classes-with-operator}

```kotlin
data class Person(
  val name: String,
  val age: Int
)

fun main() {
  val (name, age) = Person("Alice", 30)
  println("Name: $name, Age: $age")
}
```

## For loops and destructuring improvements {#For-loops-and-destructuring-improvements}

For loops can now destructure objects directly within the loop body

```kotlin
data class Person(
  val name: String,
  val age: Int
)

fun main() {
  val people = listOf(
    Person("Alice", 30),
    Person("Bob", 25)
  )
  for ((name, age) in people) {
    println("$name is $age years old")
  }
}
```

## Support for improved operators for generics and generic types {#Support-for-improved-operators-for-generics-and-generic-types}

```kotlin
class Container<T>(val value: T) {
  operator fun plus(other: Container<T>): Container<T> {
    return Container(other.value)
  }
}

fun main() {
  val container1 = Container(10)
  val container2 = Container(20)
  println(container1 + container2)
}
```

[ Copyright: Roman Kryvolapov ](https://t.me/RomanKryvolapov)