CoroutineContext Key and Element are now inside CoroutineContext interface itself (just like Map.Entry)

ContinuationInterceptor companion object is named Key
CoroutineContext.Element property for key is named just key
AbstractCoroutineContextElement implements all of CoroutineContext.Element, including key

libraries/stdlib/test/coroutines/CoroutineContextTest.kt

@@ -21,30 +21,25 @@ import org.junit.Test
 import kotlin.coroutines.*
 
 class CoroutineContextTest {
-    data class CtxA(val i: Int) : AbstractCoroutineContextElement() {
-        companion object : CoroutineContextKey<CtxA>
-        override val contextKey get() = CtxA
+    data class CtxA(val i: Int) : AbstractCoroutineContextElement(CtxA) {
+        companion object Key : CoroutineContext.Key<CtxA>
     }
 
-    data class CtxB(val i: Int) : AbstractCoroutineContextElement() {
-        companion object : CoroutineContextKey<CtxB>
-        override val contextKey get() = CtxB
+    data class CtxB(val i: Int) : AbstractCoroutineContextElement(CtxB) {
+        companion object Key : CoroutineContext.Key<CtxB>
     }
 
-    data class CtxC(val i: Int) : AbstractCoroutineContextElement() {
-        companion object : CoroutineContextKey<CtxC>
-        override val contextKey get() = CtxC
+    data class CtxC(val i: Int) : AbstractCoroutineContextElement(CtxC) {
+        companion object Key : CoroutineContext.Key<CtxC>
     }
 
-    object Disp1 : AbstractCoroutineContextElement(), ContinuationInterceptor {
+    object Disp1 : AbstractCoroutineContextElement(ContinuationInterceptor), ContinuationInterceptor {
         override fun <T> interceptContinuation(continuation: Continuation<T>): Continuation<T> = continuation
-        override val contextKey: CoroutineContextKey<*> = ContinuationInterceptor
         override fun toString(): String = "Disp1"
     }
 
-    object Disp2 : AbstractCoroutineContextElement(), ContinuationInterceptor {
+    object Disp2 : AbstractCoroutineContextElement(ContinuationInterceptor), ContinuationInterceptor {
         override fun <T> interceptContinuation(continuation: Continuation<T>): Continuation<T> = continuation
-        override val contextKey: CoroutineContextKey<*> = ContinuationInterceptor
         override fun toString(): String = "Disp2"
     }
 
@@ -171,10 +166,10 @@ class CoroutineContextTest {
         assertNotEquals(ctx3, ctx4)
     }
 
-    private fun  assertContents(ctx: CoroutineContext, vararg elements: CoroutineContextElement) {
+    private fun  assertContents(ctx: CoroutineContext, vararg elements: CoroutineContext.Element) {
         val set = ctx.fold(setOf<CoroutineContext>()) { a, b -> a + b }
         assertEquals(listOf(*elements), set.toList())
         for (elem in elements)
-            assertTrue(ctx[elem.contextKey] == elem)
+            assertTrue(ctx[elem.key] == elem)
     }
 }