I am experimenting with <kotlinx.atomicfu.locks> and found out that ```public expect inline fun <T> ...

# multiplatform

[diego-gomez-olvera]

I am experimenting with kotlinx.atomicfu.locks and found out that

public expect inline fun <T> synchronized(lock: SynchronizedObject, block: () -> T): T

as replacement of JVM synchronized misses

contract {
    callsInPlace(block, InvocationKind.EXACTLY_ONCE)
}

making the compiler unable to infer this. Is it possible to combine expect functions with contacts?

[diego-gomez-olvera]

it's possible to define it in the actual implementations, of course, but there's no guarantee that all of them respect the contract

[ephemient]

I think you'll have to use a wrapper for now,

public inline fun <T> synchronized(lock: SynchronizedObject, block: () -> T): T {
    contract {
        callsInPlace(block, InvocationKind.EXACTLY_ONCE)
    }
    return platformSynchronized(lock, block)
}
internal expect fun <T> platformSynchronized(lock: SynchronizedObject, block: () -> T): T

at least until https://youtrack.jetbrains.com/issue/KT-56127/K2-Provide-new-stable-syntax-for-contracts

[diego-gomez-olvera]

indeed. I was hoping for a built-in solution, that would work for now. Thanks for the suggestion!