[K2] Return type must be specified for NativeCoroutines declarations

[tylerwilson]

Updated to version 43, and now getting error for ever @NativeCoroutineState. See attached.

I added the nativeCoroutines { k2Mode = false } override, and that works around it.

Can we confirm whether we really need to add return type specification here?

[rickclephas]

Unfortunately explicit return types are required.
During compilation the compiler plugins will need to provide the signatures of their generated declarations.
However at that stage bodies aren't resolved yet, so implicit return types aren't available.

I highly recommend you to install the IDE plugin.
It provides quickfixes for common issues including adding the explicit return type.

[b95505017]

I've installed the plugin but it doesn't show any warning or error.

[rickclephas]

@b95505017 what version of the plugin and what version of IntelliJ or Android Studio are you using?

[b95505017]

I've found the root cause is that I didn't turn on k2 mode in the IDE.

Android Studio Meerkat Feature Drop | 2024.3.2 Patch 1
Build #AI-243.26053.27.2432.13536105, built on May 22, 2025
Runtime version: 21.0.6+-13368085-b895.109 aarch64
VM: OpenJDK 64-Bit Server VM by JetBrains s.r.o.
Toolkit: sun.lwawt.macosx.LWCToolkit
macOS 15.5
GC: G1 Young Generation, G1 Concurrent GC, G1 Old Generation
Memory: 4096M
Cores: 8
Metal Rendering is ON
Registry:
  ide.experimental.ui=true
Non-Bundled Plugins:
  io.github.composegears.valkyrie (0.14.0)
  com.rickclephas.kmp.nativecoroutines (1.0.0-ALPHA-43-idea-2024.3)
  com.jetbrains.kmm (0.8.5(243)-7)
  com.squareup.sqldelight (2.1.0)

[rickclephas]

Hmm interesting. K2 mode in the IDE shouldn't affect the checks and their quickfixes.
Just tested this with a basic project in Android Studio 2024.3.2 Patch 1 without K2 IDE mode.
Are you also using v1.0.0-ALPHA-43 in your Kotlin project itself?

[b95505017]

Yes. I'm using v1.0.0-ALPHA-43.