Fixed KT-15963 (coroutines machinery should not use equals on results)

libraries/stdlib/src/kotlin/coroutines/experimental/CoroutinesLibrary.kt

@@ -157,19 +157,16 @@ internal class SafeContinuation<in T> @PublishedApi internal constructor(private
     companion object {
         @Suppress("UNCHECKED_CAST")
         @JvmStatic
-        private val RESULT_UPDATER = AtomicReferenceFieldUpdater.newUpdater<SafeContinuation<*>, Any?>(
+        private val RESULT = AtomicReferenceFieldUpdater.newUpdater<SafeContinuation<*>, Any?>(
                 SafeContinuation::class.java, Any::class.java as Class<Any?>, "result")
     }
 
-    private fun cas(expect: Any?, update: Any?): Boolean =
-            RESULT_UPDATER.compareAndSet(this, expect, update)
-
     override fun resume(value: T) {
         while (true) { // lock-free loop
             val result = this.result // atomic read
-            when (result) {
-                UNDECIDED -> if (cas(UNDECIDED, value)) return
-                COROUTINE_SUSPENDED -> if (cas(COROUTINE_SUSPENDED, RESUMED)) {
+            when {
+                result === UNDECIDED -> if (RESULT.compareAndSet(this, UNDECIDED, value)) return
+                result === COROUTINE_SUSPENDED -> if (RESULT.compareAndSet(this, COROUTINE_SUSPENDED, RESUMED)) {
                     delegate.resume(value)
                     return
                 }
@@ -181,9 +178,9 @@ internal class SafeContinuation<in T> @PublishedApi internal constructor(private
     override fun resumeWithException(exception: Throwable) {
         while (true) { // lock-free loop
             val result = this.result // atomic read
-            when (result) {
-                UNDECIDED -> if (cas(UNDECIDED, Fail(exception))) return
-                COROUTINE_SUSPENDED -> if (cas(COROUTINE_SUSPENDED, RESUMED)) {
+            when  {
+                result === UNDECIDED -> if (RESULT.compareAndSet(this, UNDECIDED, Fail(exception))) return
+                result === COROUTINE_SUSPENDED -> if (RESULT.compareAndSet(this, COROUTINE_SUSPENDED, RESUMED)) {
                     delegate.resumeWithException(exception)
                     return
                 }
@@ -195,14 +192,14 @@ internal class SafeContinuation<in T> @PublishedApi internal constructor(private
     @PublishedApi
     internal fun getResult(): Any? {
         var result = this.result // atomic read
-        if (result == UNDECIDED) {
-            if (cas(UNDECIDED, COROUTINE_SUSPENDED)) return COROUTINE_SUSPENDED
+        if (result === UNDECIDED) {
+            if (RESULT.compareAndSet(this, UNDECIDED, COROUTINE_SUSPENDED)) return COROUTINE_SUSPENDED
             result = this.result // reread volatile var
         }
-        when (result) {
-            RESUMED -> return COROUTINE_SUSPENDED // already called continuation, indicate COROUTINE_SUSPENDED upstream
-            is Fail -> throw result.exception
-            else -> return result // either COROUTINE_SUSPENDED or data
+        when {
+            result === RESUMED -> return COROUTINE_SUSPENDED // already called continuation, indicate SUSPENDED_MARKER upstream
+            result is Fail -> throw result.exception
+            else -> return result // either SUSPENDED_MARKER or data
         }
     }
 }

libraries/stdlib/src/kotlin/coroutines/experimental/jvm/internal/CoroutineImpl.kt

@@ -51,7 +51,7 @@ abstract class CoroutineImpl(
     override fun resume(value: Any?) {
         try {
             val result = doResume(value, null)
-            if (result != COROUTINE_SUSPENDED)
+            if (result !== COROUTINE_SUSPENDED)
                 completion!!.resume(result)
         } catch (e: Throwable) {
             completion!!.resumeWithException(e)
@@ -61,7 +61,7 @@ abstract class CoroutineImpl(
     override fun resumeWithException(exception: Throwable) {
         try {
             val result = doResume(null, exception)
-            if (result != COROUTINE_SUSPENDED)
+            if (result !== COROUTINE_SUSPENDED)
                 completion!!.resume(result)
         } catch (e: Throwable) {
             completion!!.resumeWithException(e)

libraries/stdlib/test/coroutines/CoroutinesReferenceValuesTest.kt

@@ -0,0 +1,71 @@
+/*
+ * Copyright 2010-2017 JetBrains s.r.o.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package test.coroutines
+
+import kotlin.test.*
+import org.junit.Test
+import kotlin.coroutines.*
+
+/**
+ * Test to ensure that coroutine machinery does not call equals/hashCode/toString anywhere.
+ */
+class CoroutinesReferenceValuesTest {
+    class BadClass {
+        override fun equals(other: Any?): Boolean = error("equals")
+        override fun hashCode(): Int = error("hashCode")
+        override fun toString(): String = error("toString")
+    }
+
+    var counter = 0
+
+    // tail-suspend function via suspendCoroutine (test SafeContinuation)
+    suspend fun getBadClassViaSuspend(): BadClass = suspendCoroutine { cont ->
+        counter++
+        cont.resume(BadClass())
+    }
+
+    // state machine
+    suspend fun checkBadClassTwice() {
+        assertTrue(getBadClassViaSuspend() is BadClass)
+        assertTrue(getBadClassViaSuspend() is BadClass)
+    }
+
+    fun <T> suspend(block: suspend () -> T) = block
+
+    @Test
+    fun testBadClass() {
+        val bad = suspend {
+            checkBadClassTwice()
+            getBadClassViaSuspend()
+        }
+        var result: BadClass? = null
+        bad.startCoroutine(object : Continuation<BadClass> {
+            override val context: CoroutineContext = EmptyCoroutineContext
+
+            override fun resume(value: BadClass) {
+                assertTrue(result == null)
+                result = value
+            }
+
+            override fun resumeWithException(exception: Throwable) {
+                throw exception
+            }
+        })
+        assertTrue(result is BadClass)
+        assertEquals(3, counter)
+    }
+}