K2 gives error when used with kotlinx-serialization. But AFAIK, for the frontend, it only adds some minor diagnostics that I'm fine without. So could it work otherwise?

I’d like to ask why plugins are not supported. Is it because K2 changes the plugins API so all plugins must be adapted, or is it because it keeps the API but the underlying implementation is not there yet? I am starting to work on my first plugin this week and I wonder if I should consider/know about K2 when designing the plugin.

is the k2 compiler expected to compile any valid kotlin file? in one of my open source projects that compiles fine with kotlin 1.7.10 i get compile errors with k2

Tried to use k2 on internal project (kotlin 1.7.10) 1. error: 'init' hides member of supertype 'UIComponent' and needs 'override' modifier - I have a view class with

public init

method, and supertype is from library where it

internal init

- I would expect no error here (if not known, will create an issue) 2.

New inference error [NewConstraintError at Incorporate TypeVariable(T) == ft<kotlin/Any, kotlin/Any?> from Fix variable TypeVariable(T) from position Fix variable TypeVariable(T): ft<kotlin/Any, kotlin/Any?> <!: CapturedType(*)?]

- have no idea what does it mean 🙂 3.

val closeModalWindow = fun() { progressModalStage?.close() }

with K2 produces error: Return type mismatch: expected kotlin/Unit, actual kotlin/Unit? (not critical, as we can just specify type

() -> Unit

explicitly for variable) 4. several issue with generics variances and java interop, but I have no idea how to create a small reproducer without internal codebase: Assignment type mismatch: actual type is ft<javafx/collections/ObservableList<out ft<OURTYPE, OURTYPE?>>, javafx/collections/ObservableList<out ft<OURTYPE, OURTYPE?>>?> but ft<javafx/collections/ObservableList<ft<CapturedType(out OURTYPE), CapturedType(out OURTYPE)?>>, javafx/collections/ObservableList<ft<CapturedType(out OURTYPE), CapturedType(out OURTYPE)?>>?> was expected If something isn't known, I will create issues, but I will not be able to provide access to internal codebase. FYI: project using java/javafx 17 and outdated tornadofx (which latest version was published with kotlin 1.3) - so issues can be from this weird stack also

BTW: Is it possible to enable K2 in multiplatform project - only for JVM target of course?

to switch to the new k2 compiler, you need to flow a migration guide or just enable it in gradle file

I want to start adopting k2 compiler on my Android Project Where do I have to put this line ?

-Xuse-k2

Is the new Compiler Plugin extenstion API ready to be tested. if so where can we see documentation for it

Hey, I'm trying out K2 Compiler in my project which also uses kotlin-lombok plugin. As i can see in changelog, K2 supports kotlin-lombok plugin since 1.7.20-Beta version. I updated Kotlin version for both Kotlin and kotlin-lombok plugins, but K2 still shows error if i try to build my project:

There are some plugins incompatible with K2 compiler:
  org.jetbrains.kotlin.lombok.LombokComponentRegistrar
Please remove -Xuse-k2

Note that this error is different from error in 1.7.10:

e: Compiler plugins are enabled with K2 compiler.
 K2 does not support plugins yet, so please remove -Xuse-k2 flag

Did I forget to update anything?

Does K2 affects the generated code ?

Testing FIR in 1.7.20-Beta and finding the API for reporting diagnostics to be a bit limited. Few things came up • Are there plans to expose these errors in the IDE? Currently I’m not able to find any report of them in the IDE, only build-time • Are there plans to expose a way to add custom error messages to the user? Right now they are opaque reports (see first screenshot) • Currently, if both errors and warnings are reported, only the errors are shown (second screenshot) • Failure to recompile appears to break incremental compilation, or at least reports something about it (also second screenshot) • Are there plans to expose a “quickfix” or similar API to provide fixes to issues being reported? All of this is is from this branch: https://github.com/ZacSweers/redacted-compiler-plugin/compare/z/firTesting?expand=1 Happy to file bug reports or feature requests for the above issues as necessary too!

Related followup: Are there plans to support FIR-contributed changes in decompiled kotlin bytecode? • For instance - in the all-open plugin, if the FIR extension is enabled will the IDE properly render the stripped

final

modifier in decompiled bytecode? • If so, should plugin authors implement this functionality in their plugins? When would they choose to implement it in FIR vs IR in those cases?

Hiya, wanted to share a regression using K2 with Kotlin 1.7.20-Beta It's related to Curiously-Recurring Template Pattern/"_F_-bounded quantification" in TestContainers classes:

New inference error [NewConstraintError at Incorporate TypeVariable(SELF) == CapturedType(*) from Fix variable TypeVariable(SELF) from position Fix variable TypeVariable(SELF): CapturedType(*) <!: ft<org/testcontainers/containers/MySQLContainer<ft<CapturedType(*) & Any, CapturedType(*)?>>, org/testcontainers/containers/MySQLContainer<ft<CapturedType(*) & Any, CapturedType(*)?>>?>]

Where that line is:

private val container = MySQLContainer(imageName).withInitScript(initScript)

And MySQL class definition is:

public class MySQLContainer<SELF extends MySQLContainer<SELF>> extends JdbcDatabaseContainer<SELF>

These are the compiler flags I have enabled:

Hey, while we waiting for multiplatform K2, I was able to hack

rsocket-kotlin

to be jvm project instead of multiplatform: https://github.com/rsocket/rsocket-kotlin/tree/k2 And configured CI to run with and without K2 with different kotlin versions (CI run example here: https://github.com/rsocket/rsocket-kotlin/actions/runs/2914307633) And found 2 issues already: • https://youtrack.jetbrains.com/issue/KT-53698/K2-fails-to-resolve-suppressed-internal-symbol • https://youtrack.jetbrains.com/issue/KT-53699/K2-Exception-during-IR-lowering-in-code-with-coroutines Will continue creating issues if something new will happen Also will try to setup similar setup for JS and Native, when K2 for them will be ready, until K2 multiplatform support P.S. if K2 for JS/Native is already available with some highly experimental flag, please point on it, so I will setup such CI runs for them 🙂

hey folks; maven shop here,

Did K2 compilation went well?

yep. few minor fixes for type inference (+-10 lines), and having to bump up to 1.7.20-Beta due to this bug but was fine otherwise.

Have you noticed a difference in the build speed?

yep! our biggest module went from 44s to 20s on average so that’s great! overall, we see a ~25% improvement

Or what errors you encountered with, if they happened?

1. aforementioned bug 2.

value?.property

on a definitely non-null

value

was complaining, but am assuming it’s by design, so just fixed it 3. if both

kotlin-stdlib-jdk8

and

kotlin-stdlib-jre8

are somehow on path, the compiler complains about “confusing overloads”. excluding

-jre8

worked.

Hey there! I tried to use K2 with Kotlin 1.7.10, and our project uses both KSP and Compose. Both don't work, because K2 only starts supporting compiler plugins on 1.7.20. Is the Compose compiler on the agenda for 1.7.20, or do we have to wait a bit longer?

can code compiled with k2 be consumed in projects not using k2? i.e. if we wanted to enable it in subprojects that can enable it but not necessarily app

can I use @JvmRecord with k2?

seems not to work

I mitigated it by stopping to use k2 compiler for just that module which contained @JvmRecord annotated classes (a special case for faster deserialization of huge amounts of objects)

Hello! Where can I read about k2 compiler from compiler plugin development point of view?

java.lang.IllegalArgumentException: class org.jetbrains.kotlin.psi.KtParameter is not a subtype of class org.jetbrains.kotlin.psi.KtAnnotationEntry for factory REPEATED_ANNOTATION

Hey! I got this error when compiling with k2, which isn't thrown when I compile with the old compiler, lmk if you guys need more info to look into this! P.S. This is the first time I've had problem with k2 since initial release, it is surprising stable.

k2 gives different warnings for using deprecated code, can I for a specific file suppress deprecation warnings with @File (specifically, an enum class annotated with @Deprecated)

Hi there I saw the blog that says allopen is now supported in k2. Today I’ve upgraded the kotlin version to 1.7.20 and trying to switch our current spring project to use k2 compiler, and somehow the kotlin-spring plugin didn’t seem to open the classes anymore? when i switch that back to the old compiler the kotlin-spring plugin works again. I wonder if there’s anything I miss there to make kotlin-spring plugin play nicely with k2 compiler?

Hi. I'm trying to use K2 compiler in my projects. My base project builds without problem, but my derived project (building w/o K2) that uses it fails, due to "(xxx) is compiled by the new Kotlin compiler frontend and cannot be loaded by the old compiler". The error makes sense if things are essentially binary incompatible, but what feels odd to me is that I also have some modules in my base project without `useK2`in my

kotlinOptions

because they depend on Jetpack Compose (compiler plugin) but they still build (while they depend on other modules that are compiled with

useK2 = true

). Any ideas why that happens? Those builds reproduced as https://github.com/atsushieno/android-audio-plugin-framework/commit/2737fd77e176e866306329703b793e10bf8d76e7 (base) and https://github.com/atsushieno/aap-lv2/actions/runs/3384694415/jobs/5621953393#step:10:1347 (derived)

Class 'class' is compiled by a pre-release version of Kotlin and cannot be loaded by this version of the compiler

The this error is shown by the IDE despite the project using K2, and and project compiles and runs fine.

Is it valid to enable all of these flags, or do some conflict?

"-Xuse-k2",
"-Xuse-fir-extended-checkers",
"-Xuse-fir-ic",
"-Xuse-fir-lt",