Hello. I am having an issue with destructuring declarations in lambdas when compiled to javascript. ...

# javascript

[zceejkr]

Hello. I am having an issue with destructuring declarations in lambdas when compiled to javascript. To clarify:

val lam = { (a, b) ->  
  println("$a, $b")
}
lam(Pair(5, 3))

prints 5, undefined
But:

val lam = { pair ->  
  val a = pair.first
  val b = pair.second
  println("$a, $b")
}
lam(Pair(5, 3))

prints 5, 3

[anton.bannykh]

What is the type of lam? Neither snippets should compile in isolation, because the compiler cannot infer the parameter types.

The following should work though:

val lam: (Pair<Int, Int>) -> Unit = { (a, b) ->  
      println("$a, $b")
    }

    lam(Pair(5, 3))

Could you please try

val lam = { pair ->  
  val a = pair.component1()
  val b = pair.component2()
  println("$a, $b")
}
lam(Pair(5, 3))

If it fails then destructuring is not the issue here. If it work

[anton.bannykh]

If the snippets you've provided do compile on your side, please let know how. Maybe I'm missing something.

[zceejkr]

I never tried the compile the stuff I wrote, since i tried to destil the essence. In my code I am passing the lambda as an argument to another function, and I do not think the type inference is the problem since InteliJ says the snippet is OK. When I have time I will try to write an actual test that also compiles to the JVM to compare.

[anton.bannykh]

Well, I can only advise to check the componentN variant, because that's what destructuring delegates to. If it fails it's much easier to debug. If it doesn't, then it might be a compiler issue.