Revert "Introduce EXACTLY_ONCE contracts to coroutineScope, supervisorScope, withContext, runBlocking, withTimeout and select (#2030)"

This reverts commit 397f10e

Author: erokhins

integration/kotlinx-coroutines-jdk8/src/time/Time.kt

@@ -1,16 +1,13 @@
 /*
  * Copyright 2016-2020 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license.
  */
-@file:OptIn(ExperimentalContracts::class)
-
 package kotlinx.coroutines.time
 
 import kotlinx.coroutines.*
 import kotlinx.coroutines.flow.*
 import kotlinx.coroutines.selects.*
 import java.time.*
 import java.time.temporal.*
-import kotlin.contracts.*
 
 /**
  * "java.time" adapter method for [kotlinx.coroutines.delay].
@@ -38,12 +35,8 @@ public fun <R> SelectBuilder<R>.onTimeout(duration: Duration, block: suspend ()
 /**
  * "java.time" adapter method for [kotlinx.coroutines.withTimeout].
  */
-public suspend fun <T> withTimeout(duration: Duration, block: suspend CoroutineScope.() -> T): T {
-    contract {
-        callsInPlace(block, InvocationKind.EXACTLY_ONCE)
-    }
-    return kotlinx.coroutines.withTimeout(duration.coerceToMillis(), block)
-}
+public suspend fun <T> withTimeout(duration: Duration, block: suspend CoroutineScope.() -> T): T =
+        kotlinx.coroutines.withTimeout(duration.coerceToMillis(), block)
 
 /**
  * "java.time" adapter method for [kotlinx.coroutines.withTimeoutOrNull].

kotlinx-coroutines-core/common/src/Builders.common.kt

@@ -4,15 +4,13 @@
 
 @file:JvmMultifileClass
 @file:JvmName("BuildersKt")
-@file:OptIn(ExperimentalContracts::class)
 
 package kotlinx.coroutines
 
 import kotlinx.atomicfu.*
 import kotlinx.coroutines.internal.*
 import kotlinx.coroutines.intrinsics.*
 import kotlinx.coroutines.selects.*
-import kotlin.contracts.*
 import kotlin.coroutines.*
 import kotlin.coroutines.intrinsics.*
 import kotlin.jvm.*
@@ -136,36 +134,31 @@ private class LazyDeferredCoroutine<T>(
 public suspend fun <T> withContext(
     context: CoroutineContext,
     block: suspend CoroutineScope.() -> T
-): T {
-    contract {
-        callsInPlace(block, InvocationKind.EXACTLY_ONCE)
+): T = suspendCoroutineUninterceptedOrReturn sc@ { uCont ->
+    // compute new context
+    val oldContext = uCont.context
+    val newContext = oldContext + context
+    // always check for cancellation of new context
+    newContext.checkCompletion()
+    // FAST PATH #1 -- new context is the same as the old one
+    if (newContext === oldContext) {
+        val coroutine = ScopeCoroutine(newContext, uCont)
+        return@sc coroutine.startUndispatchedOrReturn(coroutine, block)
     }
-    return suspendCoroutineUninterceptedOrReturn sc@ { uCont ->
-        // compute new context
-        val oldContext = uCont.context
-        val newContext = oldContext + context
-        // always check for cancellation of new context
-        newContext.checkCompletion()
-        // FAST PATH #1 -- new context is the same as the old one
-        if (newContext === oldContext) {
-            val coroutine = ScopeCoroutine(newContext, uCont)
+    // FAST PATH #2 -- the new dispatcher is the same as the old one (something else changed)
+    // `equals` is used by design (see equals implementation is wrapper context like ExecutorCoroutineDispatcher)
+    if (newContext[ContinuationInterceptor] == oldContext[ContinuationInterceptor]) {
+        val coroutine = UndispatchedCoroutine(newContext, uCont)
+        // There are changes in the context, so this thread needs to be updated
+        withCoroutineContext(newContext, null) {
             return@sc coroutine.startUndispatchedOrReturn(coroutine, block)
         }
-        // FAST PATH #2 -- the new dispatcher is the same as the old one (something else changed)
-        // `equals` is used by design (see equals implementation is wrapper context like ExecutorCoroutineDispatcher)
-        if (newContext[ContinuationInterceptor] == oldContext[ContinuationInterceptor]) {
-            val coroutine = UndispatchedCoroutine(newContext, uCont)
-            // There are changes in the context, so this thread needs to be updated
-            withCoroutineContext(newContext, null) {
-                return@sc coroutine.startUndispatchedOrReturn(coroutine, block)
-            }
-        }
-        // SLOW PATH -- use new dispatcher
-        val coroutine = DispatchedCoroutine(newContext, uCont)
-        coroutine.initParentJob()
-        block.startCoroutineCancellable(coroutine, coroutine)
-        coroutine.getResult()
     }
+    // SLOW PATH -- use new dispatcher
+    val coroutine = DispatchedCoroutine(newContext, uCont)
+    coroutine.initParentJob()
+    block.startCoroutineCancellable(coroutine, coroutine)
+    coroutine.getResult()
 }
 
 /**

kotlinx-coroutines-core/common/src/CoroutineScope.kt

@@ -1,13 +1,11 @@
 /*
  * Copyright 2016-2020 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license.
  */
-@file:OptIn(ExperimentalContracts::class)
 
 package kotlinx.coroutines
 
 import kotlinx.coroutines.internal.*
 import kotlinx.coroutines.intrinsics.*
-import kotlin.contracts.*
 import kotlin.coroutines.*
 import kotlin.coroutines.intrinsics.*
 
@@ -185,15 +183,11 @@ public object GlobalScope : CoroutineScope {
  * or may throw a corresponding unhandled [Throwable] if there is any unhandled exception in this scope
  * (for example, from a crashed coroutine that was started with [launch][CoroutineScope.launch] in this scope).
  */
-public suspend fun <R> coroutineScope(block: suspend CoroutineScope.() -> R): R {
-    contract {
-        callsInPlace(block, InvocationKind.EXACTLY_ONCE)
-    }
-    return suspendCoroutineUninterceptedOrReturn { uCont ->
+public suspend fun <R> coroutineScope(block: suspend CoroutineScope.() -> R): R =
+    suspendCoroutineUninterceptedOrReturn { uCont ->
         val coroutine = ScopeCoroutine(uCont.context, uCont)
         coroutine.startUndispatchedOrReturn(coroutine, block)
     }
-}
 
 /**
  * Creates a [CoroutineScope] that wraps the given coroutine [context].

kotlinx-coroutines-core/common/src/Supervisor.kt

@@ -1,14 +1,13 @@
 /*
  * Copyright 2016-2020 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license.
  */
-@file:OptIn(ExperimentalContracts::class)
+
 @file:Suppress("DEPRECATION_ERROR")
 
 package kotlinx.coroutines
 
 import kotlinx.coroutines.internal.*
 import kotlinx.coroutines.intrinsics.*
-import kotlin.contracts.*
 import kotlin.coroutines.*
 import kotlin.coroutines.intrinsics.*
 import kotlin.jvm.*
@@ -48,15 +47,11 @@ public fun SupervisorJob0(parent: Job? = null) : Job = SupervisorJob(parent)
  * A failure of the scope itself (exception thrown in the [block] or cancellation) fails the scope with all its children,
  * but does not cancel parent job.
  */
-public suspend fun <R> supervisorScope(block: suspend CoroutineScope.() -> R): R {
-    contract {
-        callsInPlace(block, InvocationKind.EXACTLY_ONCE)
-    }
-    return suspendCoroutineUninterceptedOrReturn { uCont ->
+public suspend fun <R>  supervisorScope(block: suspend CoroutineScope.() -> R): R =
+    suspendCoroutineUninterceptedOrReturn { uCont ->
         val coroutine = SupervisorCoroutine(uCont.context, uCont)
         coroutine.startUndispatchedOrReturn(coroutine, block)
     }
-}
 
 private class SupervisorJobImpl(parent: Job?) : JobImpl(parent) {
     override fun childCancelled(cause: Throwable): Boolean = false

kotlinx-coroutines-core/common/src/Timeout.kt

@@ -1,14 +1,12 @@
 /*
  * Copyright 2016-2020 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license.
  */
-@file:OptIn(ExperimentalContracts::class)
 
 package kotlinx.coroutines
 
 import kotlinx.coroutines.internal.*
 import kotlinx.coroutines.intrinsics.*
 import kotlinx.coroutines.selects.*
-import kotlin.contracts.*
 import kotlin.coroutines.*
 import kotlin.coroutines.intrinsics.*
 import kotlin.jvm.*
@@ -29,9 +27,6 @@ import kotlin.time.*
  * @param timeMillis timeout time in milliseconds.
  */
 public suspend fun <T> withTimeout(timeMillis: Long, block: suspend CoroutineScope.() -> T): T {
-    contract {
-        callsInPlace(block, InvocationKind.EXACTLY_ONCE)
-    }
     if (timeMillis <= 0L) throw TimeoutCancellationException("Timed out immediately")
     return suspendCoroutineUninterceptedOrReturn { uCont ->
         setupTimeout(TimeoutCoroutine(timeMillis, uCont), block)
@@ -51,12 +46,8 @@ public suspend fun <T> withTimeout(timeMillis: Long, block: suspend CoroutineSco
  * Implementation note: how the time is tracked exactly is an implementation detail of the context's [CoroutineDispatcher].
  */
 @ExperimentalTime
-public suspend fun <T> withTimeout(timeout: Duration, block: suspend CoroutineScope.() -> T): T {
-    contract {
-        callsInPlace(block, InvocationKind.EXACTLY_ONCE)
-    }
-    return withTimeout(timeout.toDelayMillis(), block)
-}
+public suspend fun <T> withTimeout(timeout: Duration, block: suspend CoroutineScope.() -> T): T =
+        withTimeout(timeout.toDelayMillis(), block)
 
 /**
  * Runs a given suspending block of code inside a coroutine with a specified [timeout][timeMillis] and returns

kotlinx-coroutines-core/common/src/selects/Select.kt

@@ -1,7 +1,6 @@
 /*
  * Copyright 2016-2020 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license.
  */
-@file:OptIn(ExperimentalContracts::class)
 
 package kotlinx.coroutines.selects
 
@@ -11,7 +10,6 @@ import kotlinx.coroutines.channels.*
 import kotlinx.coroutines.internal.*
 import kotlinx.coroutines.intrinsics.*
 import kotlinx.coroutines.sync.*
-import kotlin.contracts.*
 import kotlin.coroutines.*
 import kotlin.coroutines.intrinsics.*
 import kotlin.jvm.*
@@ -201,11 +199,8 @@ public interface SelectInstance<in R> {
  * Note that this function does not check for cancellation when it is not suspended.
  * Use [yield] or [CoroutineScope.isActive] to periodically check for cancellation in tight loops if needed.
  */
-public suspend inline fun <R> select(crossinline builder: SelectBuilder<R>.() -> Unit): R {
-    contract {
-        callsInPlace(builder, InvocationKind.EXACTLY_ONCE)
-    }
-    return suspendCoroutineUninterceptedOrReturn { uCont ->
+public suspend inline fun <R> select(crossinline builder: SelectBuilder<R>.() -> Unit): R =
+    suspendCoroutineUninterceptedOrReturn { uCont ->
         val scope = SelectBuilderImpl(uCont)
         try {
             builder(scope)
@@ -214,7 +209,6 @@ public suspend inline fun <R> select(crossinline builder: SelectBuilder<R>.() ->
         }
         scope.getResult()
     }
-}
 
 
 @SharedImmutable

kotlinx-coroutines-core/common/test/BuilderContractsTest.kt

@@ -4,12 +4,10 @@
 
 @file:JvmMultifileClass
 @file:JvmName("BuildersKt")
-@file:OptIn(ExperimentalContracts::class)
 
 package kotlinx.coroutines
 
 import java.util.concurrent.locks.*
-import kotlin.contracts.*
 import kotlin.coroutines.*
 
 /**
@@ -36,9 +34,6 @@ import kotlin.coroutines.*
  */
 @Throws(InterruptedException::class)
 public fun <T> runBlocking(context: CoroutineContext = EmptyCoroutineContext, block: suspend CoroutineScope.() -> T): T {
-    contract {
-        callsInPlace(block, InvocationKind.EXACTLY_ONCE)
-    }
     val currentThread = Thread.currentThread()
     val contextInterceptor = context[ContinuationInterceptor]
     val eventLoop: EventLoop?

kotlinx-coroutines-core/jvm/src/Builders.kt

@@ -162,13 +162,4 @@ class RunBlockingTest : TestBase() {
 
         handle.dispose()
     }
-
-    @Test
-    fun testContract() {
-        val rb: Int
-        runBlocking {
-            rb = 42
-        }
-        rb.hashCode() // unused
-    }
 }