KotlinScala

KotlinScala is a statically typed language for the Java Virtual Machine that blends features from Kotlin and Scala. It aims to combine Kotlin's emphasis on safety and concise syntax with Scala's expressive type system and functional programming capabilities. Designed for teams that maintain both Kotlin and Scala codebases, KotlinScala provides interoperability and a unified development experience on the JVM and related runtimes.

Design goals include strong null safety, rich type inference, and support for functional programming constructs such as higher-order functions, algebraic data types, and pattern matching. The language adopts Kotlin-style extension functions and coroutines alongside Scala-inspired functional abstractions, blending them into a coherent model. It also features interoperable mechanisms to enable generic programming without sacrificing readability, drawing on both languages' historically strong type systems.

Runtime and interoperability: KotlinScala compiles to JVM bytecode, enabling direct use of existing Kotlin and Scala libraries. It provides bidirectional interop paths, allowing KotlinScala code to call Kotlin and Scala APIs seamlessly, and to be called from Kotlin and Scala code. The standard library combines subsets of both ecosystems and adds unified support for collections, data types, and error handling, with clear boundaries to minimize interop friction.

Tooling and ecosystem: The project emphasizes integration with IDEs such as IntelliJ IDEA and build tools like Gradle and Maven, plus a compiler extension framework for language enhancements. Adoption trends point to polyglot JVM projects seeking to reuse existing codebases, with ongoing work to stabilize the interop surface and improve the learning curve. Performance targets aim to be competitive with Kotlin and Scala, particularly for long-running or concurrent applications.

See also: Kotlin, Scala, JVM languages.