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One thing to be aware of with api/language level 1.5+ is that lambdas are transformed to `invokedynamic` calls, which can cause issues with <https://docs.gradle.org/current/userguide/validation_problems.html#implementation_unknown|up-to-date checking> and the <https://docs.gradle.org/nightly/userguide/configuration_cache.html#config_cache:not_yet_implemented:storing_lambdas|configuration cache>. `-Xsam-conversions=class` works around it.

It's less of a problem than it used to be because there's <https://github.com/gradle/gradle/blob/d76f249d1b725a6e31bb72a3636888cf4847f069/subprojects/core/src/main/java/org/gradle/internal/classpath/InstrumentingTransformer.java#L516|some crazy magic in the bytecode transformer for the build classpath> that special cases `Action&lt;T&gt;` and `Spec&lt;T&gt;`, but it can still be problematic for other things like `Function&lt;T, R&gt;`.

ah, good catch. We set `-Xsam-conversions=class` for all our gradle plugins

Can you provide what I should add to my workaround to enable `sam-conversions`?  I can add a comment next to it regarding your comment.

```afterEvaluate {
    tasks.withType&lt;KotlinCompile&gt;().configureEach {
        kotlinOptions {
            apiVersion = "1.5"
            languageVersion = "1.5"
        }
    }
}```

Does this look right?
```kotlinOptions {
        freeCompilerArgs += ['-Xsam-conversions=class']
    }```

this is what I have in my codebase
```tasks.withType(org.jetbrains.kotlin.gradle.tasks.KotlinCompile).configureEach {
  kotlinOptions {
    // Resolves warning of this sort when using the configuration cache:
    // Execution optimizations have been disabled for task ':module:testDebugUnitTest' to ensure
    // correctness due to the following reasons:
    //  - Additional action of task ':module:testDebugUnitTest' was implemented by the Java lambda
    //  'com.squareup.gradle.support.UnitTestAgentPlugin$apply$1$2$$Lambda$5945/0x0000001783f92440'.
    //  Reason: Using Java lambdas is not supported as task inputs.
    freeCompilerArgs += '-Xsam-conversions=class'
  }
}```