Try-finally and non-local returns - Mutex.withLock

[Laxystem]

Try-finally and non-local returns - Mutex.withLock

[dkhalanskyjb]

This is not a problem with the library: you're not even supposed to read the source code to use it, so "I don't understand why the implementation works properly" is not something we consider a bug. Especially, we are not going to write comments about fundamental language constructs like try and return. Here's a good explanation of how finally works: https://docs.oracle.com/javase/tutorial/essential/exceptions/finally.html and here's an explanation of inline functions: https://kotlinlang.org/docs/inline-functions.html

[mgroth0]

This issue has me a bit worried but also a bit confused. You ask "do finallys apply to non-local returns?", but wouldn't this take a minute to test? My understanding was that code inside a finally block always executes, no matter what.

If you could create a small reproducer of a case where code inside of a finally is not executed, I would like to see it.

[mgroth0]

fun main() {
    val mutex = Mutex()
    suspend fun foo(): Int =
        mutex.withLock {
            return 42
        }
    runBlocking {
        val result = foo()
        println("result=$result")
        println("isLocked=${mutex.isLocked}")
    }
}

Output:

result=42
isLocked=false

I am confused if you have ever observed a finally block not running, or if this is just a misunderstanding.

[Laxystem]

I'm saying the documentation should be changed, because this can be confusing.