Serialization fails with Kotlin 2.0.0-Beta4 and K2 Kapt flag enabled

[aftabahmadTW]

Describe the bug
Not sure if this is the best place to report it. I was trying out Kotlin 2.0.0-Beta4 in our company codebase. When trying it with kapt.use.k2 set to true, we noticed that we were getting errors in the generated code for serialization.

Stack trace provided:

> Task :app:kaptGenerateStubsDebugKotlin
w: K2 kapt is an experimental feature. Use with caution.

> Task :app:kaptDebugKotlin FAILED
serialization/app/build/tmp/kapt3/stubs/debug/com/sample/serialization/response/SampleResponse.java:94: error: illegal '.'
        public static final com.sample.serialization.response.SampleResponse..serializer INSTANCE = null;

You can see it generates the code with a double dot here: SampleResponse..serializer

To Reproduce
serialization.zip

I attached a small sample which highlights this issue. If you set kapt.use.k2=false then the project compiles and runs however setting it to true causes the issue above.

Hopefully the sample is useful.

Expected behavior
I would expect that kapt doesn't interfere with kotlinx-serialization.

Environment

• Kotlin version: 2.0.0-Beta4
• Library version: 1.6.3
• Kotlin platforms: Android
• Gradle version: 8.2
• Other relevant context: kapt.use.k2=true

[pdvrieze]

Does the serialization work without kapt but with the k2 compiler enabled?

[aftabahmadTW]

Yes, if kapt isn't involved it works or if the flag kapt.use.k2 is false that also works.

[sandwwraith]

Looks like you've already filed https://youtrack.jetbrains.com/issue/KT-66147 which is resolved by https://youtrack.jetbrains.com/issue/KT-65399 in Beta-5