Tips and Tricks

Scala 3 Overview: What’s New and What Has Changed?

Scala has long been a powerful programming language, marrying the best features of functional and object-oriented programming. With the release of Scala 3, significant changes and improvements have been made. This article delves into what makes Scala 3 special, how to transition from Scala 2, and insights from industry experts.

Why Scala 3 Matters

Scala 3 matters because it addresses limitations in Scala 2 and introduces features that enhance productivity, readability, and performance. It standardizes many experimental features and brings forth new language constructs that make coding in Scala more expressive and robust.

  • Standardization of Features

Scala 2 had various experimental features that developers often hesitated to adopt due to concerns about future compatibility. Scala 3 standardizes many of these experimental elements, providing a more stable platform for development and encouraging wider community adoption.

  • Enhanced Productivity

Scala 3 introduces features like optional braces, improved type inference, and first-class enums that simplify the syntax and make it easier to write concise yet powerful code. This enhances developer productivity, as less time needs to be spent on writing boilerplate code or deciphering complex type errors.

  • Compiler Innovations

The Scala 3 compiler, known as Dotty, brings a host of optimizations and improvements. From emitting more efficient bytecode to advanced features like union types and dependent function types, the compiler plays a crucial role in making Scala 3 faster and more efficient.

New Features in Scala 3

Enumerations: Enhanced Expressiveness

Scala 3 introduces first-class enumerations, offering a more robust and straightforward way to model data that can exist as one of a finite set of options. Unlike Scala 2, where you had to use sealed traits and case objects, Scala 3’s enums are simpler to declare and more expressive.

enum Planet {

  case Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune


This feature also supports parameterized enums and allows you to define methods within enum classes, providing a powerful tool for modeling domain-specific logic.

Optional Braces: Cleaner Syntax

The introduction of optional braces aims to simplify Scala’s syntax by reducing visual clutter. This feature aligns well with Scala’s goal to be a clean and straightforward language and allows for more readable code.

if x > 0 then


The language provides clear rules on when braces can be omitted, ensuring that the code remains unambiguous.

Top-level Definitions: Simplified Structure

Scala 3 allows developers to define methods and values at the top level of a file, doing away with the need for a main method inside an object. This change makes Scala more accessible to newcomers and simplifies scripting.

// top-level value

val greeting = "Hello, World!"

// top-level method

def sayHello(): Unit =


Improved Type Inference: Smarter Compiler

Type inference in Scala 3 has received significant upgrades, making it smarter and reducing the amount of type-related boilerplate code. This enhancement particularly helps when working with complex data structures or function signatures, making code cleaner and more maintainable.

val numbers = List(1, 2, 3)  // Compiler infers List[Int]

Contextual Abstractions: Improved Readability and Usability

Scala 3 introduces new contextual abstractions like given/using syntax, which are set to replace implicits. These new abstractions are more straightforward to use and understand, thereby improving code readability and maintainability.

given Ordering[Int] with

  def compare(x: Int, y: Int): Int = x - y

def sort[T](list: List[T])(using ordering: Ordering[T]): List[T] = ???

Match Expressions: Exhaustiveness and Flexibility

Scala 3 adds enhancements to pattern matching, including safer handling of match expressions through exhaustiveness checks and improved flexibility with match types. This addition makes it easier to write robust and type-safe code.

// Exhaustiveness check

x match {

  case _: Int => println("It's an Int")

  case _: String => println("It's a String")

  // Compiler warning if other types are not handled


Multiverse Equality: Type-safe Comparisons

Scala 3 introduces a new feature called Multiverse Equality, which prevents unintended equality checks between unrelated types, making your programs less error-prone.

if x === y then // Compile-time check for type compatibility


Each of these new features in Scala 3 brings specific advantages to the table, from boosting productivity and improving code quality to enabling new programming paradigms. Whether you’re working on large codebases or small projects, these enhancements collectively make Scala 3 a highly capable and flexible language for modern software development.

Migrating from Scala 2 to Scala 3

Scala 3 is designed to be backward-compatible with Scala 2 to a large extent, there are some breaking changes and deprecated features. Here’s what you need to know to make the migration process as smooth as possible.

  1. Preparation: Understanding the Changes

Before starting the migration, it’s essential to understand what’s new, deprecated, or removed in Scala 3. Scala provides a comprehensive migration guide detailing these aspects, and spending time on this can help avoid surprises later on.

  1. Automated Tools: Scala 3 Migrator

The Scala 3 Migrator tool is designed to automate many of the changes required for migration. It not only identifies the portions of code that need modification but also attempts to automatically rewrite them in Scala 3 syntax. While it might not handle all edge cases, it’s a significant aid in reducing manual effort.

  1. Dependency Management: Cross-building

For projects with multiple dependencies, Scala 3 allows cross-building with Scala 2.13, facilitating a smoother transition. Libraries that your project depends on might still be on Scala 2; cross-building helps you maintain compatibility with these while adopting Scala 3 features.

// build.sbt

crossScalaVersions := Seq("2.13.6", "3.0.0")
  1. Syntax and Language Features

Scala 3 introduces new syntax and language features that may replace or deprecate older Scala 2 constructs. You’ll need to update your code to comply with these new features. For instance, if your Scala 2 code heavily uses implicits, you might want to refactor it to use the new given/using constructs in Scala 3.

  1. Testing: Thorough Validation

Given the range of new features and changes in Scala 3, comprehensive testing is critical. Automated tests, if already in place, are extremely beneficial here. They provide a safety net and allow you to verify that existing functionalities still work as expected after the migration.

  1. Performance Implications

Scala 3 offers several compiler optimizations that can lead to performance gains. However, it’s advisable to benchmark your application both before and after the migration to ensure that there are no unexpected performance regressions.

  1. Community and Ecosystem Support

When migrating, check the compatibility of third-party libraries and plugins. Many popular Scala libraries have already been ported to Scala 3, but some may still be in transition. You might need to find alternatives or temporary solutions for incompatible libraries.

  1. Phased Migration

For larger codebases and teams, a phased migration might be more manageable. You can initially migrate a smaller, non-critical component of your application to Scala 3 and gradually proceed to more significant parts, learning from each step and making adjustments to your migration strategy.

FeatureScala 2Scala 3
EnumsUtilized sealed traitsFirst-class enums
Top-level DefinitionsNot SupportedSupported
Type InferenceLimitedImproved
Comparative Analysis: Scala 2 vs Scala 3

Expert Opinion

Having worked extensively with both Scala 2 and Scala 3, I can confidently say that the shift to Scala 3 is not just evolutionary — it’s revolutionary. The changes go far beyond mere syntactic sugar or incremental enhancements; they represent a fundamental rethinking of how Scala should work, driven by a decade’s worth of experience and community feedback.

One of the most striking things about Scala 3 is how it’s geared towards the future. In the technology world, standing still is equivalent to moving backward. Scala 3 addresses this by incorporating the latest academic research and industrial use-cases into its design. This proactive approach ensures that Scala remains relevant, efficient, and modern.

Scala has always been a language that allows you to express complex ideas in a straightforward manner. Scala 3 takes this a step further by introducing features like optional braces and improved type inference. These features simplify the language without sacrificing its power, allowing both newcomers and experienced developers to be more productive.


Q: Is Scala 3 backward-compatible with Scala 2?

A: Scala 3 is largely backward-compatible but does include breaking changes. However, tools are available for easing migration.

Q: How do enums in Scala 3 differ from sealed traits in Scala 2?

A: Scala 3 enums are more concise, expressive, and come with built-in pattern matching support, unlike sealed traits in Scala 2.

Q: What are the performance implications of Scala 3?

A: Scala 3 aims for better performance through improved JVM bytecode generation and other compiler optimizations.


Scala 3 is more than just an incremental update; it brings groundbreaking changes that streamline the development process and improve code quality. Whether you’re a seasoned Scala developer or new to the language, Scala 3 offers compelling reasons to make the switch.

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