[not sure this is the right channel so let me know if there's a better place] I'm trying context receivers and tried to write an alternative "scoping" function but it didn't work:

class Logging {
  val logger = java.util.logging.Logger.getLogger("test")
}

context(Logging)
fun hello() {
  <http://logger.info|logger.info>("Hello")
}

fun <C, R> within(ctx: C, call: context(C) () -> R): R = call(ctx)

fun main() {
  within(Logging()) {
    hello() // Error: No required context receiver found: Cxt { context(Logging) public fun hello(): kotlin.Unit defined [...]
  }
}

Is this supposed to be this way or it's just something not yet implemented in the prototype version?

Works for me:

class Logger {
    fun info(message: String) {
        println("INFO: $message")
    }
}

class Logging {
    val logger = Logger()
}

context(Logging)
fun hello() {
    <http://logger.info|logger.info>("Hello")
}

fun <R> within(ctx: Logging, call: context(Logging) () -> R): R = call(ctx)

fun main() {
    with(Logging()) {
        hello()
    }

    within(Logging()) {
        hello() // Error: No required context receiver found: Cxt { context(Logging) public fun hello(): kotlin.Unit defined [...]
    }
}

The above seems to happen if context receivers are not enabled for the compiler. Could you try this

build.gradle.kts

?

@file:Suppress("UNUSED_VARIABLE")

plugins {
    kotlin("multiplatform") version "1.6.20-M1"
    application
}

repositories {
    mavenCentral()
}

kotlin {
    jvm {
        compilations.all {
            kotlinOptions {
                jvmTarget = "1.8"
                freeCompilerArgs += listOf("-Xcontext-receivers")
            }
        }
        withJava()
    }
    sourceSets {
        val jvmMain by getting
        val jvmTest by getting
    }
}

application {
    mainClass.set("MainKt")
}

I tried sth very similar but with two context parameters and it worked when i moved the lambda into a local variable and provided the type explicitly. So it works, also autocompletion in the lambda and so on, but not with an inline lambda, thats why i think its a bug.

I had overlooked that I had removed the first type parameter from

within

. As soon as I re-introduce it (

C

), the error reappears. So yes, seems to be a bug.

Thanks for the report. I created the issue, looking into it.