open class D { }

class D1 : D() { }

open class C {
    open fun D.foo() {
        println("D.foo in C")
    }

    open fun D1.foo() {
        println("D1.foo in C")
    }

    fun caller(d: D) {
        d.foo()   // call the extension function
    }
}

class C1 : C() {
    override fun D.foo() {
        // Is there some way to get something like super.foo() on this receiver?
        println("D.foo in C1")
    }

    override fun D1.foo() {
        println("D1.foo in C1")
    }
}

fun main() {
    C().caller(D())   // prints "D.foo in C"
    C1().caller(D())  // prints "D.foo in C1" - dispatch receiver is resolved virtually
    C().caller(D1())  // prints "D.foo in C" - extension receiver is resolved statically
}

assertThat(validate("true").asBoolean().getOrThrow(), `is`(instanceOf(Boolean::class.java))) // old - hamcrest
assertThat(validate("true").asBoolean().getOrThrow()).isInstanceOf(Boolean::class.java) // new - assertj

Expecting:
  <true>
to be an instance of:
  <boolean>
but was instance of:
  <java.lang.Boolean>

infix function

KFunction1

( root child "node" ) { 
    it attr "child node 1"
    it childValue "child node 2"
    it childValue "child node 3"
}

lazy

Warning:kotlin: Runtime JAR files in the classpath should have the same version. These files were found in the classpath:
    .../.gradle/caches/modules-2/files-2.1/org.jetbrains.kotlin/kotlin-stdlib-jdk7/1.2.31/95d6a67e8787280a82a2059e54e4db7ac6cfe74/kotlin-stdlib-jdk7-1.2.31.jar (version 1.2)
    .../.gradle/caches/modules-2/files-2.1/org.jetbrains.kotlin/kotlin-stdlib-jdk8/1.2.31/50094b02ec8a4c2e4444073c722bb56c8a52b83c/kotlin-stdlib-jdk8-1.2.31.jar (version 1.2)
    .../.gradle/caches/modules-2/files-2.1/org.jetbrains.kotlin/kotlin-reflect/1.3.10/dd02865be0351707554b16a896b766b2396cdafa/kotlin-reflect-1.3.10.jar (version 1.3)
    .../.gradle/caches/modules-2/files-2.1/org.jetbrains.kotlin/kotlin-stdlib/1.3.30/9ea98e65c246d34de9af59c104ad9bdea4908ee/kotlin-stdlib-1.3.30.jar (version 1.3)
    .../.gradle/caches/modules-2/files-2.1/org.jetbrains.kotlin/kotlin-stdlib-common/1.3.30/989a125fdb6e4d0d75a016032e03e1e3b57a13d/kotlin-stdlib-common-1.3.30.jar (version 1.3)h

kotlin-stdlib-jdk7:1.3.21

kotlin-stdlib-jdk8:1.3.21

this

T

Delegates.observable

var foo: Foo? = null
        set(value) {
            field = value
            update()
        }

    var foo2: Foo? by Delegates.observable(null as Foo?) {
        prop, old, new -> update()
    }

Delegates.observable

import com.google.common.truth.Subject
import kotlin.contracts.contract

inline fun <reified T> Subject<*, *>.isInstanceOf() {
  contract {
    returns() implies (this@isInstanceOf is T)
  }
  isInstanceOf(T::class.java)
}

compareTo

// No actual instantiation of class 'Password' happens
// At runtime 'securePassword' contains just 'String'
val securePassword = Password("Don't try this in production")

inline class Identifier(val value: String)

subList

fun <T> List.subVector(i: Int, length: Int): List<T> = subList(i, i + length)

val

val log: Log = MyLogImpl()

log.d("...")

val