Kotlin Multiplatform Jun 23, 2025

v2.2.0

What's New

Kotlin 2.2.0 delivers major stability improvements to the K2 compiler with 30+ Analysis API fixes, full context parameter support across all tooling, and performance optimizations for type inference and SAM conversion. New features include context-sensitive resolution, WASM annotation instantiation, and JVM default methods enabled by default, while deprecated language versions 1.8-1.9 encourage migration to modern Kotlin.

Highlights

Breaking Changes

  • Language versions 1.8 and 1.9 deprecated, users should upgrade to 2.0 or later
  • KaClassLikeSymbol.classIdIfNonLocal renamed to classId
  • KtCallableSymbol.callableIdIfNonLocal renamed to callableId
  • ForbidParenthesizedLhsInAssignments changed from error to warning

Deprecations

  • -Xextended-compiler-checks flag deprecated in favor of deprecation cycle
  • kotlin.concurrent.AtomicRef<Int> usage now generates warning diagnostic
  • Discourage usage of kotlin.concurrent Native atomics in favor of new atomics API

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