Hi, why are the results different? ```fun main() { val a: () -> Unit = { } val b: () -&gt...

# announcements

[Kefas]

Hi, why are the results different?

fun main() {
    val a: () -> Unit = { }
    val b: () -> Unit = { }
    val c = generateLambda()
    val d = generateLambda()

    println(a == b) // false
    println(c == d) // true
}

fun generateLambda(): () -> Unit {
    return { }
}

[Kefas]

https://play.kotlinlang.org/#eyJ2ZXJzaW9uIjoiMS41LjIxIiwicGxhdGZvcm0iOiJqYXZhIiwiYXJncy[…]xhbWJkYSgpOiAoKSAtPiBVbml0IHtcbiAgICByZXR1cm4geyB9XG59In0=

[Zach Klippenstein (he/him) [MOD]]

i think it’s because the compiler creates a separate lambda object for each lambda in the source code. The lambdas on line 2 and line 3 are different (they’re each on separate lines), so the compiler generates an object for each. It also generates an object for the lambda inside generateLambda. However, because those lambdas don’t capture any variables/properties, it only generates a single instance of each one, which is why calling generateLambda multiple times returns the same object. Just a guess, I don’t remember exactly how the latest kotlin compilers actually do lambdas.

[Kefas]

Thanks, yeah, it generates multiple instances if the lambda captures external variables

[smit01]

Is it possible if We could figure this out by looking at bytecode?

[Zach Klippenstein (he/him) [MOD]]

yep

[Youssef Shoaib [MOD]]

IIRC, basically the compiler has an optimisation for lambdas when they don't capture any values, and so in this case generateLambda returns a singleton

[Youssef Shoaib [MOD]]

TBH I'd love to see a compiler plugin that has full equality for lambdas based on the code inside of them