Add EXACTLY_ONCE contract to functions that call their lambda parameter once

KT-35972

libraries/stdlib/src/kotlin/text/StringBuilder.kt

@@ -1,5 +1,5 @@
 /*
- * Copyright 2010-2018 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * 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.
  */
 
@@ -8,6 +8,8 @@
 
 package kotlin.text
 
+import kotlin.contracts.*
+
 /**
  * A mutable sequence of characters.
  *
@@ -399,8 +401,10 @@ public inline fun StringBuilder.append(obj: Any?): StringBuilder = this.append(o
  * and then converting it to [String].
  */
 @kotlin.internal.InlineOnly
-public inline fun buildString(builderAction: StringBuilder.() -> Unit): String =
-    StringBuilder().apply(builderAction).toString()
+public inline fun buildString(builderAction: StringBuilder.() -> Unit): String {
+    contract { callsInPlace(builderAction, InvocationKind.EXACTLY_ONCE) }
+    return StringBuilder().apply(builderAction).toString()
+}
 
 /**
  * Builds new string by populating newly created [StringBuilder] initialized with the given [capacity]
@@ -408,8 +412,10 @@ public inline fun buildString(builderAction: StringBuilder.() -> Unit): String =
  */
 @SinceKotlin("1.1")
 @kotlin.internal.InlineOnly
-public inline fun buildString(capacity: Int, builderAction: StringBuilder.() -> Unit): String =
-    StringBuilder(capacity).apply(builderAction).toString()
+public inline fun buildString(capacity: Int, builderAction: StringBuilder.() -> Unit): String {
+    contract { callsInPlace(builderAction, InvocationKind.EXACTLY_ONCE) }
+    return StringBuilder(capacity).apply(builderAction).toString()
+}
 
 /**
  * Appends all arguments to the given StringBuilder.

libraries/stdlib/src/kotlin/time/Duration.kt

@@ -1,10 +1,11 @@
 /*
- * Copyright 2010-2019 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * 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 kotlin.time
 
+import kotlin.contracts.*
 import kotlin.math.abs
 
 @OptIn(ExperimentalTime::class)
@@ -104,8 +105,10 @@ public inline class Duration internal constructor(internal val value: Double) :
      *   If the value doesn't fit in [Int] range, i.e. it's greater than [Int.MAX_VALUE] or less than [Int.MIN_VALUE],
      *   it is coerced into that range.
      */
-    public inline fun <T> toComponents(action: (days: Int, hours: Int, minutes: Int, seconds: Int, nanoseconds: Int) -> T): T =
-        action(inDays.toInt(), hoursComponent, minutesComponent, secondsComponent, nanosecondsComponent)
+    public inline fun <T> toComponents(action: (days: Int, hours: Int, minutes: Int, seconds: Int, nanoseconds: Int) -> T): T {
+        contract { callsInPlace(action, InvocationKind.EXACTLY_ONCE) }
+        return action(inDays.toInt(), hoursComponent, minutesComponent, secondsComponent, nanosecondsComponent)
+    }
 
     /**
      * Splits this duration into hours, minutes, seconds, and nanoseconds and executes the given [action] with these components.
@@ -118,8 +121,10 @@ public inline class Duration internal constructor(internal val value: Double) :
      *   If the value doesn't fit in [Int] range, i.e. it's greater than [Int.MAX_VALUE] or less than [Int.MIN_VALUE],
      *   it is coerced into that range.
      */
-    public inline fun <T> toComponents(action: (hours: Int, minutes: Int, seconds: Int, nanoseconds: Int) -> T): T =
-        action(inHours.toInt(), minutesComponent, secondsComponent, nanosecondsComponent)
+    public inline fun <T> toComponents(action: (hours: Int, minutes: Int, seconds: Int, nanoseconds: Int) -> T): T {
+        contract { callsInPlace(action, InvocationKind.EXACTLY_ONCE) }
+        return action(inHours.toInt(), minutesComponent, secondsComponent, nanosecondsComponent)
+    }
 
     /**
      * Splits this duration into minutes, seconds, and nanoseconds and executes the given [action] with these components.
@@ -131,8 +136,10 @@ public inline class Duration internal constructor(internal val value: Double) :
      *   If the value doesn't fit in [Int] range, i.e. it's greater than [Int.MAX_VALUE] or less than [Int.MIN_VALUE],
      *   it is coerced into that range.
      */
-    public inline fun <T> toComponents(action: (minutes: Int, seconds: Int, nanoseconds: Int) -> T): T =
-        action(inMinutes.toInt(), secondsComponent, nanosecondsComponent)
+    public inline fun <T> toComponents(action: (minutes: Int, seconds: Int, nanoseconds: Int) -> T): T {
+        contract { callsInPlace(action, InvocationKind.EXACTLY_ONCE) }
+        return action(inMinutes.toInt(), secondsComponent, nanosecondsComponent)
+    }
 
     /**
      * Splits this duration into seconds, and nanoseconds and executes the given [action] with these components.
@@ -143,8 +150,10 @@ public inline class Duration internal constructor(internal val value: Double) :
      *   If the value doesn't fit in [Long] range, i.e. it's greater than [Long.MAX_VALUE] or less than [Long.MIN_VALUE],
      *   it is coerced into that range.
      */
-    public inline fun <T> toComponents(action: (seconds: Long, nanoseconds: Int) -> T): T =
-        action(inSeconds.toLong(), nanosecondsComponent)
+    public inline fun <T> toComponents(action: (seconds: Long, nanoseconds: Int) -> T): T {
+        contract { callsInPlace(action, InvocationKind.EXACTLY_ONCE) }
+        return action(inSeconds.toLong(), nanosecondsComponent)
+    }
 
     @PublishedApi
     internal val hoursComponent: Int get() = (inHours % 24).toInt()