i've finally found how to disable IDE warnings:

compileKotlin {
    kotlinOptions {
        freeCompilerArgs = ['-Xuse-experimental=kotlinx.coroutines.ObsoleteCoroutinesApi']
    }
}

I really think it should be in the docs somewhere... I had the same problem.

Do you know how to do it for maven project?

nope, sorry. i hope jb guys will implement ide automatic intention for it

I think this is a better version:

tasks.withType(org.jetbrains.kotlin.gradle.tasks.KotlinCompile).all {
    kotlinOptions {
        freeCompilerArgs += [
                '-Xuse-experimental=kotlinx.coroutines.ObsoleteCoroutinesApi',
                '-Xuse-experimental=kotlinx.coroutines.ExperimentalCoroutinesApi'
        ]
    }
}

The

+=

adds more options (just in case you already have some elsewhere), and

Experimental

is for things like

Dispatchers.Unconfined

.

If these flags are enabled, it seems like the coroutines API has to be on the build classpath even if the project does not reference them. Is that right?

Not sure. There's a KEEP on

use-experimental

though... for me I just put this where I do have it on my classpath.

That would be the normal situation, but I have a custom build plugin with common config, and wanted to add these values there (but consumers of the plugin don't necessarily use coroutines).

I think this has to do with the new experimental flags in Kotlin so it might not be directly linked to coroutines. Maybe in #gradle or #build-tools someone might have a better idea...

I think maybe #compiler

For inline classes and unsigned`s etc...?

I was getting a warning with an annotation like

@UseExperimental(ObsoleteCoroutinesApi::class)

Oh, that makes sense! Just funny that I don't think I needed it...

I guess I should be using

@ObsoleteCoroutinesApi

directly

For me it fails the build when a module does not have it present:

e: Experimental API marker kotlinx.coroutines.ObsoleteCoroutinesApi is unresolved. Please make sure it's present in the module dependencies
e: Experimental API marker kotlinx.coroutines.ExperimentalCoroutinesApi is unresolved. Please make sure it's present in the module dependencies
> Task :rx:compileDebugKotlin FAILED

Is there a solution for this?

@Paul Woitaschek https://youtrack.jetbrains.com/issue/KT-27709

Any workaround? 1.3.20 sounds like it's far away

Adding the compiler options or the annotations to code using it.