Kotlin v2.4.20-RC

Changelog

Backend. J2KLIB

• KT-88165 Add Support for -XheaderModeType=compilation to improve header compilation performance
• KT-86239 [JKLIB] Investigate which type system context is needed in JklibIrLinker
• KT-88306 [JKLIB] Unbound symbols for kotlin.coroutines.SuspendFunctionN
• KT-88120 [JKLIB] Add -jvm-target to K2JKlibCompilerArguments
• KT-88176 [JKLIB] DeserializationStrategy.WITH_INLINE_BODIES when deserializaing dependencies
• KT-88163 Allow to disable firAggressivePrunner for Jklib

Compiler

• KT-87499 ClassCastException "Float cannot be cast to Unit" when a suspend function's result is discarded in a when-branch
• KT-87983 CCE on member extension property delegated to bound property reference
• KT-85403 kotlin.NoWhenBranchMatchedException on Kotlin Native with sealed interface
• KT-87922 K1FakeDescriptorsForReferencesKt classes duplicated between kotlin-scripting-compiler-embeddable and kotlin-build-tools-impl
• KT-86657 Native: turn on incremental compilation by default

Compose compiler

• b/543684938 Fix composable singleton in function with type parameters
• b/537617330 Fixed a bug that caused miscompilation of cross-module calls       to getters and setters, causing spurious runtime errors.

JVM. Reflection

• KT-87369 Reflection: KClass.members fails on Java class with self-referential raw type bounds

Tools. Build Tools API

• KT-88348 MessageCollector in IncrementalCompilerRunner drops diagnostics IDs
• KT-87743 Make KotlinCoreEnvironment.disposeApplicationEnvironment() unnecessary for K2 BTA compilation

Tools. CLI

• KT-87868 In-process compilation via CLI/Build Tools API pays a large ThreadMXBean.getCurrentThreadUserTime penalty on Linux: PerformanceManager.measureSideTime measures unconditionally around every class file read

Tools. Compiler Plugins

• KT-88179 Power-assert: IrGenerationExtensionException (StringIndexOutOfBoundsException) when assert() wraps a context-parameter function call

Tools. Compiler plugins. Compose

• KT-88028 Compose compiler: IndexOutOfBoundsException in ComposableTargetAnnotationsTransformer when overriding a @Composable function with default parameter in another module

Tools. Gradle

• KT-87994 Run Gradle integration tests against Gradle 9.7
• KT-87993 Compile against Gradle API 9.7
• KT-87256 KotlincOutputParser fails to parse compilation errors under Gradle when task path prefixes are enabled (Kotlin 2.4.20-Beta1)
• KT-88084 Each build leaves a strong reference to an instance of BuildMetricsService
• KT-87911 Report an actionable diagnostic when .kar files reach compilation classpaths in Kotlin 2.4.20
• KT-86040 Run tests against the Gradle 9.6.0 release

Tools. Gradle. Multiplatform

• KT-87790 Kotlin 2.4.0 increases Gradle sync times
• KT-88104 dumpXcodebuildArgs task fails if the root build directory is removed
• KT-88154 Swift PM lock file is ignored on switching version from exact to from

Tools. Gradle. Wasm

• KT-88115 "Your lockfile needs to be updated": Outdated bundled yarn.lock breaks kotlinWasmToolingSetup with --frozen-lockfile

Tools. Scripts

• KT-87958 K2 scripting: FirPropertyImpl transformation crash when using class from @file:Import-ed script in 2.4.0+