Introduce CancellationException

#KT-39126 Fixed

libraries/stdlib/test/coroutines/cancellation/CancellationExceptionTest.kt

@@ -0,0 +1,37 @@
+/*
+ * Copyright 2010-2020 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
+package coroutines.cancellation
+
+import kotlin.coroutines.cancellation.CancellationException
+import kotlin.test.Test
+import kotlin.test.assertEquals
+
+class CancellationExceptionTest {
+
+    @Test
+    fun testAllConstructors() {
+        // Mostly test NO_ACTUAL_WITHOUT_EXPECT though
+        val cause = ArithmeticException()
+        val message = "message"
+        checkException(CancellationException(message, cause), cause, message)
+        checkException(CancellationException(message, null), null, message)
+        checkException(CancellationException(cause), cause, cause.defaultMessage())
+        checkException(CancellationException(message), null, message)
+        // TODO doesn't work on js ir KT-39964
+//        checkException(CancellationException(null, cause), cause, null)
+        checkException(CancellationException(cause = cause), cause, cause.defaultMessage())
+        // does not work on JVM because of typealias
+//      checkException(CancellationException(message = message), null, message)
+        checkException(CancellationException(), null, null)
+    }
+
+    private fun Throwable?.defaultMessage() = toString()
+
+    private fun checkException(e: CancellationException, expectedCause: Throwable?, expectedMessage: String?) {
+        assertEquals(expectedCause, e.cause)
+        assertEquals(expectedMessage, e.message)
+    }
+}