Why donesn t this compile ``` fun functionImpl a Int b String fun nonSuspending function Int String gt Unit fun suspending function suspend Int String gt Unit fun test nonSuspending functionImpl suspending functionImpl ```

fun functionImpl(a: Int, b: String) {}

fun nonSuspending(function: (Int, String) -> Unit) {}
fun suspending(function: suspend (Int, String) -> Unit) {}

fun test() {
  nonSuspending(::functionImpl)
  suspending(::functionImpl)
}

Marc Dietrichstein

10/09/2019, 7:35 AM

fun suspending

requires a

suspend

function but you pass

functionImpl

which is not a

suspend

function The following code works for example:

fun functionImpl(a: Int, b: String) {}
suspend fun functionImplSuspending(a: Int, b: String) {}

fun nonSuspending(function: (Int, String) -> Unit) {}
fun suspending(function: suspend (Int, String) -> Unit) {}

fun test() {
    nonSuspending(::functionImpl)
    suspending(::functionImplSuspending)
}

Paul Woitaschek

10/09/2019, 7:36 AM

I know; but why?

Hm https://youtrack.jetbrains.com/issue/KT-15917

The design resolution is that conversion from regular functions to suspending function will be supported.

Looks like it will be implemented. But it's from '17. I just refactored several classes from rxjava to flow and this made the migration a pain @elizarov

elizarov

10/09/2019, 11:01 AM

Tentatively in 1.4.0. It requires a new type inference engine.

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