Idea: Passing an array to a `vararg` parameter usi...

# language-proposals

[Marc Knaup]

Idea: Passing an array to a vararg parameter using vararg keyword.
Reason: Make code easier to read & understand (one keyword in both locations), simplify language (no extra unary * operator needed)
Esp. helpful for people who are new to Kotlin or have only rarely if ever use spread operators in other languages.

Example:

ByteString.of(*buffer.toByteArray())

->

ByteString.of(vararg buffer.toByteArray())

At the declaration-site vararg denotes "variadic number of parameters".
At the call-site vararg denotes "variadic number of arguments".

[Marc Knaup]

Some previous discussion in #general:
https://kotlinlang.slack.com/archives/C0922A726/p1559228766021300

[Pavlo Liapota]

As @Dico pointed out you can use spread operator several times and even combine it with other values for the same parameter:

ByteString.of(1, *byteArrayOf(2, 3), 4, 5, *byteArrayOf(6, 7))

And vararg instead of * is less readable in this case.

[Marc Knaup]

That's an interesting (yet potentially rare) case indeed.
Using vararg would make it longer and less concise, yes.
It could still be more readable and comprehensible esp. in more complex cases where it's not that easy to spot these * and immediately see their meaning.

[poohbar]

I just wish the * worked on arrays and Lists. I am always tripped up by it.

[Matej Drobnič]

Yeah arrays are second class citizens in Kotlin (all operators on arrays return lists, which practically forces you to use lists) and yet you have to convert to array to use spread

[Matej Drobnič]

plus debugging arrays is cumbersome (I always forget to wrap it in Arrays.toString and get garbage output)

[karelpeeters]

https://youtrack.jetbrains.com/issue/KT-12663