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The Kotlin Programming Language
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igoriakovlev Fix UL classes descriptors leaks
UL classes built upon descriptors and UL support classes are saving a descriptors.
This could lead to descriptors leakage so we have to eliminate any fields with descriptor references.

Fixed #KT-34337
Latest commit bc66834 Oct 14, 2019
Type Name Latest commit message Commit time
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.idea Refactor debugger tests Oct 8, 2019
android-studio Prepare building plugins modules against 1.8 JDK Apr 4, 2016
annotations Remove KotlinSignature annotations from project code Oct 13, 2015
ant Build: Fix manifest for kotlin-compiler in jps build Jun 27, 2019
benchmarks FIR: eliminate most usages of FirSession.service() and getService() Oct 8, 2019
build-common JS: add -Xmetadata-only flag for JS common code modules (KT-33142 fixed) Sep 27, 2019
buildSrc Handle case when property is missed Oct 15, 2019
compiler Fix UL classes descriptors leaks Oct 21, 2019
core Don't render pure error types in OverrideMemberChooserObject Oct 21, 2019
dependencies Refactor more tasks to lazy API Aug 21, 2019
docs Mention the `master` branch as the target of pull requests in contrib… Sep 2, 2019
generators New J2K: add multi-file conversion tests from old j2k Oct 12, 2019
gradle Advance 193 version to 193.4697-EAP-CANDIDATE-SNAPSHOT Oct 17, 2019
idea-runner Build: Fix usages of "java.home" for tools.jar dependency Sep 25, 2019
idea Fix UL classes descriptors leaks Oct 21, 2019
include Refactor more tasks to lazy API Aug 21, 2019
j2k idea: cleanup "Remove redundant qualifier name" Oct 17, 2019
jps-plugin Ensure all output roots exist after Kotlin is compiled in JPS Sep 30, 2019
js [KLIB] Fix `explicitlyExported` mode Oct 21, 2019
konan Gradle, native: Add a DSL shortcut for iOS, watchsOS and tvOS Oct 11, 2019
libraries [Gradle, JS] Fix for wildcard npm dependency version Oct 21, 2019
license Fix license information for js modules Oct 11, 2019
nj2k idea: cleanup "Remove redundant qualifier name" Oct 17, 2019
plugins Provide a diagnostic when @serializable annotation is missing on enum. Oct 21, 2019
prepare [CLI] add support running scripts in js compiler, extract common code… Oct 10, 2019
resources Inline some properties from that were used … May 5, 2017
spec-docs Type parameters are placed before the name of the function Aug 19, 2019
test-instrumenter Fix nullability in the instrumenter, avoid exceptions on tests setup Jul 15, 2019
third-party KT-29586: Add android.annotation annotations Jan 31, 2019
.bunch Fix bunch rule Oct 2, 2019
.gitattributes Exclude generated test classes from language statistics Jan 3, 2018
.gitignore Add patched kotlin-source-map-loader Oct 4, 2019 Code of Conduct for Kotlin project Feb 19, 2019 Add changelog for 1.3.50 Oct 8, 2019 Updated switch usage in README Sep 2, 2019
build.gradle.kts Remove embeddable tests - they are causing conflicts... Oct 19, 2019 Build: flags for comparing gradle and jps Jun 27, 2019 Build: flags for comparing gradle and jps Jun 27, 2019 Build: flags for comparing gradle and jps Jun 27, 2019 as36: Add bunches for AS 3.6 C6 based on 192 platform Jul 25, 2019
gradlew Build: Upgrade gradle to 5.4.1 Jul 1, 2019
gradlew.bat Build: Upgrade gradle to 5.4.1 Jul 1, 2019
settings.gradle Rename cidr-native -> common-cidr-native Oct 17, 2019
upload_plugins.gradle.kts Build: Rewrite upload_plugins.gradle in Kotlin Aug 16, 2019

official project TeamCity (simple build status) Maven Central GitHub license

Kotlin Programming Language

Welcome to Kotlin! Some handy links:

Editing Kotlin

Build environment requirements

In order to build Kotlin distribution you need to have:

  • JDK 1.6, 1.7, 1.8 and 9

  • Setup environment variables as following:

      JAVA_HOME="path to JDK 1.8"
      JDK_16="path to JDK 1.6"
      JDK_17="path to JDK 1.7"
      JDK_18="path to JDK 1.8"
      JDK_9="path to JDK 9"

For local development, if you're not working on bytecode generation or the standard library, it's OK to have only JDK 1.8 and JDK 9 installed, and to point JDK_16 and JDK_17 environment variables to your JDK 1.8 installation.

You also can use Gradle properties to setup JDK_* variables.

Note: The JDK 6 for MacOS is not available on Oracle's site. You can download it here.

On Windows you might need to add long paths setting to the repo:

git config core.longpaths true 


The project is built with Gradle. Run Gradle to build the project and to run the tests using the following command on Unix/macOS:

./gradlew <tasks-and-options>

or the following command on Windows:

gradlew <tasks-and-options>

On the first project configuration gradle will download and setup the dependencies on

  • intellij-core is a part of command line compiler and contains only necessary APIs.
  • idea-full is a full blown IntelliJ IDEA Community Edition to be used in the plugin module.

These dependencies are quite large, so depending on the quality of your internet connection you might face timeouts getting them. In this case you can increase timeout by specifying the following command line parameters on the first run:

./gradlew -Dhttp.socketTimeout=60000 -Dhttp.connectionTimeout=60000

Important gradle tasks

  • clean - clean build results
  • dist - assembles the compiler distribution into dist/kotlinc/ folder
  • ideaPlugin - assembles the Kotlin IDEA plugin distribution into dist/artifacts/Kotlin folder
  • install - build and install all public artifacts into local maven repository
  • runIde - build IDEA plugin and run IDEA with it
  • coreLibsTest - build and run stdlib, reflect and kotlin-test tests
  • gradlePluginTest - build and run gradle plugin tests
  • compilerTest - build and run all compiler tests
  • ideaPluginTest - build and run all IDEA plugin tests

OPTIONAL: Some artifacts, mainly Maven plugin ones, are built separately with Maven. Refer to libraries/ for details.

Building for different versions of IntelliJ IDEA and Android Studio

Kotlin plugin is intended to work with several recent versions of IntelliJ IDEA and Android Studio. Each platform is allowed to have a different set of features and might provide a slightly different API. Instead of using several parallel Git branches, project stores everything in a single branch, but files may have counterparts with version extensions (*.as32, *.172, *.181). The primary file is expected to be replaced with its counterpart when targeting non-default platform.

More detailed description of this scheme can be found at

Usually, there's no need to care about multiple platforms as all features are enabled everywhere by default. Additional counterparts should be created if there's an expected difference in behavior or an incompatible API usage is required and there's no reasonable workaround to save source compatibility. Kotlin plugin contains a pre-commit check that shows a warning if a file has been updated without its counterparts.

Development for some particular platform is possible after 'switching' that can be done with Bunch Tool from the command line.

cd kotlin-project-dir

# switching to IntelliJ Idea 2018.2
bunch switch 182

Working with the project in IntelliJ IDEA

Working with the Kotlin project requires at least IntelliJ IDEA 2017.3. You can download IntelliJ IDEA 2017.3 here.

After cloning the project, to import the project in Intellij choose the project directory in the Open project dialog. Then, after project opened, Select File -> New... -> Module from Existing Sources in the menu, and select build.gradle.kts file in the project's root folder.

In the import dialog, select use default gradle wrapper.

To be able to run tests from IntelliJ easily, check Delegate IDE build/run actions to Gradle and choose Gradle Test Runner in the Gradle runner settings after importing the project.

At this time, you can use the latest released 1.2.x version of the Kotlin plugin for working with the code. To make sure you have the latest version installed, use Tools | Kotlin | Configure Kotlin Plugin Updates and press "Check for updates now".

Compiling and running

From this root project there are Run/Debug Configurations for running IDEA or the Compiler Tests for example; so if you want to try out the latest and greatest IDEA plugin

  • VCS -> Git -> Pull
  • Run the "IDEA" run configuration in the project
  • a child IntelliJ IDEA with the Kotlin plugin will then startup

Including into composite build

To include kotlin compiler into composite build you need to define dependencySubstitution for kotlin-compiler module in settings.gradle

includeBuild('/path/to/kotlin') {
    dependencySubstitution {
        substitute module('org.jetbrains.kotlin:kotlin-compiler') with project(':include:kotlin-compiler')


Kotlin is distributed under the terms of the Apache License (Version 2.0). See license folder for details.


Please be sure to review Kotlin's contributing guidelines to learn how to help the project.

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