I would like this to be possible :smile: It should...

# language-proposals

[Marc Knaup]

I would like this to be possible 😄
It should call Foo.invoke() rather than treating it as a trailing lambda since none is expected.

fun main() {
    makeFoo() { // Too many arguments for public fun makeFoo(): Foo defined in root package in file main.kt
        42
    }
}

fun makeFoo() = Foo()

class Foo {
    operator fun invoke(arg: () -> Int) {
        println(arg())
    }
}

[Fleshgrinder]

Doesn’t (makeFoo()) {} work? It’s typical for IIFE to require some additional parenthesis to work properly because otherwise it’s impossible to parse. 😛

[Fleshgrinder]

It’s like the classic if () {} if () {} else {} problem.

[Marc Knaup]

It would work, but it doesn’t make a nice DSL 😅

Too bad that it’s hard to parse 😕

[diesieben07]

makeFoo()() { ... } also works

[Marc Knaup]

Why the heck does that work 😂

[Marc Knaup]

Ah, I see

[Marc Knaup]

confusing 😄

[diesieben07]

If you want to make it a nice DSL you can do:

val makeFoo get() = Foo()

[diesieben07]

Then makeFoo { } works

[Fleshgrinder]

… and add inline too. 😉

[Marc Knaup]

@diesieben07 it’s a generic function unfortunately.

[Marc Knaup]

In my case

[Fleshgrinder]

Funnel the lambda through.

[Marc Knaup]

Yeah that’s what I’m doing through extensions now. Repetitive but a solution.

[Fleshgrinder]

Does your invoke actually require access to the innter state? Otherwise you could drop makeFoo and move the invoke to the companion.

[Marc Knaup]

Yeah it does. Basically similar to the Gradle Kotlin Script API 😮

[Fleshgrinder]

Free standing construction functions mostly make sense in multi-platform projects where one wants to delegate the decision of how things are constructed from some expect to some actual. A companion operator fun invoke is almost always nicer in a JVM project. 😉

[Marc Knaup]

Functions have better auto completion imo

[Fleshgrinder]

Extension functions in companions where bad so far but with the rest I don't see much of a difference. Free-standing functions are in general harder to find because it's not clear what belong to which class.

[Fleshgrinder]

Or vice versa…

[Marc Knaup]

I keep getting autocompletion of companion invokes as

SomeClass.invoke(…) or even SomeClass.Companion.invoke(…)

[Fleshgrinder]

Are you on the latest stable? EAP doesn’t have such issues.

[Marc Knaup]

Haven’t tested with .70 yet