Random

The companion object Random.Companion is the default instance of Random.

Random.Default

operator fun contains

object Links {
    <values here>

    operator fun contains(link: String) = when (link) {
        HELP, SHOP, BLOG, ... -> true
        else -> false
    }
}

try-catch-null-check.kt:22:24: error: operator call corresponds to a dot-qualified call 'nullableVal.plus(1)' which is not allowed on a nullable receiver 'nullableVal'.
	val sum = nullableVal + 1
                       ^

::

Companion

class Foo(bar: () -> Bar)

class Bar {
    companion object {
        fun newInstance() = Bar()
    }
}
....
Foo(Bar.Companion::newInstance) //<--- works
Foo(Bar::newInstance) //<--- doesn't work

Collection<...>

Collection<String>

Collection<Closeable>

when

Array<String>?

String?

Array<String>?

null

Class<Map<String, Any>>

Any

K2JVMCompiler

java.*

-no-jdk

List

val lines = reply.split("\n")

fun `kotlin is pretty smart`(){
    val nullableSet: Set<Int>? = setOf(1, 2, 3)
    
    when(nullableSet?.size){ 
        null -> {}
        else -> { nullableSet.first() }
    }
}

nullableSet!!

well the expression

nullableSet?.size

wasn't null, and

size

can never be null, so

nullableSet

must also not be null, so I can smart-cast it to

Set<Int>

class Ref<T: Ref<T>> { ... }
class RefHolder<T: Ref<T>> { ... }

class Source {
    val refs: MutableList<RefHolder<*>> = ...
    ...
}

fun <T: Ref<T>> serializeRef(ref: RefHolder<T>, ...): ... { ... }

fun serializeSource(source: Source): ... {
  val refs = source.refs.map { serializeRef(it, ...) }  // Cannot resolve type as it: Ref<*>
}

serializeRef

serializeRef(it as RefHolder<Nothing>, ...)

entries

entries

list.map{ ... }