Scala 3 is a major revision of the Scala programming language which has many new features. Technically, Scala is a statically-typed object-oriented language that combines functional and object-oriented programming paradigms.
In Scala 3, many new features and improvements have been added. It features a revamped type system that is more consistent and predictable. This change allows for new features such as union types, and also results in a more streamlined experience for developers, with improved type inference and overload resolution.
In this article, we provide a quick overview of the most significant changes and exploring new features of Scala 3. A few references are available for you if you want to dig deeper:
What’s new in Scala 3
Type System Improvements
In addition to providing more efficient type inference, the updated type system in Scala 3 also offers a variety of new features that allow developers to express constraints and invariants within the types themselves. This gives programmers more powerful tools for ensuring the correctness of their code and making it more robust.
The implementation of enums in Scala 3 has been redesigned to better integrate with case classes and provide a more consistent way to express algebraic data types. This new approach for enums is intended to become the standard for expressing this type of data in Scala.
Scala 3 enumerations are highly customizable, they can be parameterized and can have additional properties or methods. They will also come with a set of pre-defined methods that can be used to perform common tasks.
Here’s an example of a parameterized enumeration:
Opaque types allow you to create an abstraction barrier in your code by hiding implementation details behind type aliases, without incurring the performance penalty that is often associated with similar techniques such as value classes. This means you can use opaque types to create more powerful and expressive abstractions, without sacrificing performance.
Here’s an example of how to create an opaque type alias for a
Long value that represents a user’s Id:
You can then use the
UserId type in your code, just like you would use a regular type:
UserId is an opaque type, the implementation details of the underlying
Long value are hidden, making it more difficult for clients of your code to accidentally use the value in an inappropriate way.
Intersection and union types
The new type system in Scala 3 has been built on new foundations, which allows for the introduction of new features such as intersection and union types. Intersection types, represented by
A & B, are types that are instances of both
B. Union types, represented by
A | B, are types that are instances of either
B. These constructs give programmers greater flexibility in expressing type constraints that are not limited to the inheritance hierarchy. This allows developers to express complex relationships between types in a more intuitive and expressive way.
An intersection type is written as
A & B, which represents a type that has all the members of both
An example of an intersection type is:
A union type is written as
A | B, which represents a type that is either type
A or type
An example of a union type is:
In the above example,
x is of type
String | Int. When we match
x, it could be either
Int, depending on the value it holds.
The updated type system is more principled and expressive, allowing for improved type inference, better overload resolution, and new features like union types. The redesign of enums to blend well with case classes and form the new standard for algebraic data types also adds to the overall improvement in the type system. These changes make the language more intuitive and easier to use, while still providing the power and expressiveness that Scala is known for. Ultimately, the type system improvements in Scala 3 bring the language closer to its goal of being a modern and flexible language for functional programming.