Hi. I’m using a third-party Kotlin library compiled for JVM 1.6. My application is targeting JVM 1.8. When I try to compile my code that calls an inline higher-order function in the library, I get the following compilation error:

Error:(17, 5) Kotlin: Cannot inline bytecode built with JVM target 1.8 into bytecode that is being built with JVM target 1.6. Please specify proper '-jvm-target' option

What’s the solution to this?

Make sure that Kotlin is also targeting jdk8, not just Java. For example, in gradle:

apply plugin: 'java'
apply plugin: "kotlin"

sourceCompatibility = '1.8'
targetCompatibility = '1.8'

compileKotlin {
    kotlinOptions {
        jvmTarget = '1.8'
    }
}

I think that’s why I’m getting the error … My code is being compiled to 1.8 because of that

kotlinOptions.jvmTarget

declaration in Gradle, but the bytecode it’s being inlined into is 1.6 bytecode in the library my code depends on.

why is your code inlined into the library code? shouldnt it be the other way around?

The library defines an inline higher order function

you could copy that one source file to your own project.

The library is mostly higher-order functions.

Which library is this?

In this case it’s minutest.

I think I’ve figured it out. Setting the Kotlin version in

compileKotlin {}

doesn’t set the same value for the

test

sourceset. Try adding

compileTestKotlin {
    kotlinOptions {
        jvmTarget = "1.8"
    }
}

to my snippet above

Thanks! You’re a star

Better to use withType<KotlinCompile> to configure all available Kotlin tasks