I want to draw attention to an idea of chained `wh...

# language-proposals

[Alexander Kuklev]

I want to draw attention to an idea of chained `when`’s by @Wout Werkman:

val m = list.min().when { NoSuchElement -> 0 }

someExpression.when { 
  it < 0   -> Int.MIN_VALUE
  it > 100 -> Int.MAX_VALUE
}.doOtherStuff()

Default else branch is obviously else -> it. We propose only allowing the anonymous parameter `it`; if you need to name it, use the ordinary when.

Chained `when`’s seem to be the perfect fit for rich errors where the elvis operator :? is no longer, but have great applications otherwise.

[joseph_ivie]

I'm split on this. when looks too much like an extension function with a lambda and it's hard to distinguish. On the other hand, this is really clean.
Come to think of it, when as it stands bugs me a bit for the same reason. if and the other controls don't have the same problem because they already act really closely to a function with a lambda input, but when magically treats its curly braces differently from both class declarations AND function bodies.

[JP Sugarbroad]

Pipeline operator? https://github.com/tc39/proposal-pipeline-operator