test: Kotlin syntax test file

tests/syntax-tests/source/Kotlin/test.kt

@@ -0,0 +1,85 @@
+import kotlin.math.*
+
+data class Example(
+    val name: String,
+    val numbers: List<Int?>
+)
+
+fun interface JokeInterface {
+    fun isFunny(): Boolean
+}
+
+abstract class AbstractJoke : JokeInterface {
+    override fun isFunny() = false
+    abstract fun content(): String
+}
+
+class Joke : AbstractJoke() {
+    override fun isFunny(): Boolean {
+        return true
+    }
+    override fun content(): String = "content of joke here, haha"
+}
+
+class DelegatedJoke(val joke: Joke) : JokeInterface by joke {
+    val number: Long = 123L
+
+    companion object {
+        const val someConstant = "some constant text"
+    }
+}
+
+object SomeSingleton
+
+sealed class Shape {
+    abstract fun area(): Double
+}
+
+data class Square(val sideLength: Double) : Shape() {
+    override fun area(): Double = sideLength.pow(2)
+}
+
+object Point : Shape() {
+    override fun area() = .0
+}
+
+class Circle(val radius: Double) : Shape() {
+    override fun area(): Double {
+        return PI * radius * radius
+    }
+}
+
+fun String.extensionMethod() = "test"
+
+fun main() {
+    val name = """
+       multiline
+       string
+       
+       some numbers: 123123 42
+    """.trimIndent()
+    val example = Example(name = name, numbers = listOf(512, 42, null, -1))
+
+    example.numbers
+        .filterNotNull()
+        .forEach { println(it) }
+
+    setOf(Joke(), DelegatedJoke(Joke()).joke)
+        .filter(JokeInterface::isFunny)
+        .map(AbstractJoke::content)
+        .forEachIndexed { index: Int, joke ->
+            println("I heard a funny joke(#${index + 1}): $joke")
+        }
+
+    listOf(Square(12.3), Point, Circle(5.2))
+        .associateWith(Shape::area)
+        .toList()
+        .sortedBy { it.second }
+        .forEach {
+            println("${it.first}: ${it.second}")
+        }
+
+    println("some string".extensionMethod())
+
+    require(SomeSingleton::class.simpleName == "SomeSingletonName") { "something does not seem right..." }
+}