```inline fun test crossinline callback gt Unit callback ```

Question

```inline fun test crossinline callback gt Unit callback ``` The doc says some `inline` functions may call the lambdas passed to them as parameters not directly from the function body but from another execution context such as a local object or a nested function which I understood as an `inline` function is not allowed to call the `crossinline` parameter directly in its scope But why does the code snippet works and I was able to call `callback ` directly Does the doc meant to say that you can call the `crossinline` argument directly and within another local scope as well

Joffrey · Answer

Yes the `crossinline` modifier allows you to use the argument in other scopes in addition to being able to use it directly It does so by forbidding non local returns inside the lambda that is passed on the call site

Joffrey · Answer

So what you re forbidding with this `crossinline` is this kind of usage ```fun someOtherFun calling test with a non local return that tries to return from someOtherFun test return compile error due to crossinline ```

The Monster · Answer

Ok looks like I misunderstood the docs then because of the phrase not directly from the function body which confused the heck out of me Can I think if `crossinline` as hybrid then The `crossinline` makes the lambda argument `hybrid` in the sense that it can be used in other scopes like `noinline` ~but cannot have non local control flow like `inline` ~

The Monster · Answer

wait hold on maybe not the `inline` can have return

Joffrey · Answer

Yes in a way Basically you can have 3 levels `noinline` doesn t inline the lambda at all so you can pass it around store it in variables use it in nested scopes etc but you cannot use non local returns because it s not inlined in the call site so it wouldn t make sense `crossinline` is inlined but because it can be inlined in nested contexts you have to give up non local returns so you don t mess up the control flow in the nested functions that will call that lambda regular inline you can use non local returns on the call site but on the flip side you cannot nest it in other contexts inside the inline function body

Joffrey · Answer

Essentially when you inline stuff you cannot have non local returns in nested contexts because that would mess up the control flow So you either don t use your lambda argument in nested contexts regular inline or you give up non local returns `crossinline`

The Monster · Answer

inline can return cannot be used in other scope noinline cannot return can be used in other scope crossinline cannot return can be used in other scope with crossinline lose return ability from inline gain scope ability from noinline

The Monster · Answer

Thank you so much sir I get it now

Joffrey · Answer

One note you could add to your differences table above is that the difference between noinline and crossinline is well that the former is not inlined slightly smiling face This means for instance that with `noinline` you can assign the lambda argument to a variable which you cannot do with an inline lambda

Joffrey · Answer

```inline fun test callback gt Unit val x = callback forbidden inline fun test noinline callback gt Unit val x = callback allowed ```

The Monster · Answer

I was reading this article <https www baeldung com kotlin crossinline vs noinline> and it does not mention variable assignment at all So it s nice that you notice that special detail Thank you for the heads up