[utils] Move atMostOne to core/util.runtime

There is nothing backend-specific about this helper function.

compiler/backend-common/src/org/jetbrains/kotlin/backend/common/CollectionUtil.kt

@@ -1,16 +0,0 @@
-/*
- * Copyright 2000-2019 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 org.jetbrains.kotlin.backend.common
-
-fun <T> Collection<T>.atMostOne(): T? {
-    return when (this.size) {
-        0 -> null
-        1 -> this.iterator().next()
-        else -> throw IllegalArgumentException("Collection has more than one element.")
-    }
-}
-
-inline fun <T> Iterable<T>.atMostOne(predicate: (T) -> Boolean): T? = this.filter(predicate).atMostOne()

compiler/backend-common/src/org/jetbrains/kotlin/backend/common/SimpleMemberScope.kt

@@ -11,6 +11,7 @@ import org.jetbrains.kotlin.name.Name
 import org.jetbrains.kotlin.resolve.scopes.DescriptorKindFilter
 import org.jetbrains.kotlin.resolve.scopes.MemberScopeImpl
 import org.jetbrains.kotlin.utils.Printer
+import org.jetbrains.kotlin.utils.atMostOne
 
 class SimpleMemberScope(val members: List<DeclarationDescriptor>) : MemberScopeImpl() {
 

compiler/ir/backend.common/src/org/jetbrains/kotlin/backend/common/lower/StringConcatenationLowering.kt

@@ -18,7 +18,7 @@ package org.jetbrains.kotlin.backend.common.lower
 
 import org.jetbrains.kotlin.backend.common.CommonBackendContext
 import org.jetbrains.kotlin.backend.common.FileLoweringPass
-import org.jetbrains.kotlin.backend.common.atMostOne
+import org.jetbrains.kotlin.utils.atMostOne
 import org.jetbrains.kotlin.ir.builders.*
 import org.jetbrains.kotlin.ir.declarations.*
 import org.jetbrains.kotlin.ir.expressions.IrExpression

compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/JsCommonBackendContext.kt

@@ -8,7 +8,7 @@ package org.jetbrains.kotlin.ir.backend.js
 import org.jetbrains.kotlin.backend.common.BackendContext
 import org.jetbrains.kotlin.backend.common.CommonBackendContext
 import org.jetbrains.kotlin.backend.common.InlineClassesUtils
-import org.jetbrains.kotlin.backend.common.atMostOne
+import org.jetbrains.kotlin.utils.atMostOne
 import org.jetbrains.kotlin.descriptors.ClassDescriptor
 import org.jetbrains.kotlin.descriptors.ModuleDescriptor
 import org.jetbrains.kotlin.descriptors.PropertyDescriptor

compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/lower/coroutines/AbstractSuspendFunctionsLowering.kt

@@ -33,6 +33,7 @@ import org.jetbrains.kotlin.ir.visitors.IrElementVisitorVoid
 import org.jetbrains.kotlin.ir.visitors.acceptChildrenVoid
 import org.jetbrains.kotlin.ir.visitors.acceptVoid
 import org.jetbrains.kotlin.name.Name
+import org.jetbrains.kotlin.utils.atMostOne
 import org.jetbrains.kotlin.utils.memoryOptimizedMap
 import org.jetbrains.kotlin.utils.memoryOptimizedMapIndexed
 import org.jetbrains.kotlin.utils.memoryOptimizedPlus

core/util.runtime/src/org/jetbrains/kotlin/utils/CollectionUtil.kt

@@ -47,3 +47,31 @@ inline fun <reified T, reified R, C : MutableCollection<in R>> Iterable<*>.filte
     }
     return destination
 }
+
+/**
+ * Returns the single element of the collection if it contains at most one element.
+ *
+ * If the collection is empty, returns `null`.
+ *
+ * If the collection contains exactly one element, returns that element.
+ *
+ * If the collection contains more than one element, throws an exception.
+ */
+fun <T> Collection<T>.atMostOne(): T? {
+    return when (size) {
+        0 -> null
+        1 -> this.iterator().next()
+        else -> throw IllegalArgumentException("Collection has more than one element.")
+    }
+}
+
+/**
+ * Returns at most one element from the iterable that satisfies the given predicate.
+ *
+ * If there are no elements that satisfy [predicate], returns `null`.
+ *
+ * If there is exactly one element that satisfies [predicate], returns that element.
+ *
+ * If there are more such elements, throws an exception.
+ */
+inline fun <T> Iterable<T>.atMostOne(predicate: (T) -> Boolean): T? = this.filter(predicate).atMostOne()

core/util.runtime/src/org/jetbrains/kotlin/utils/MemoryOptimizedCollectionUtil.kt

@@ -104,12 +104,13 @@ infix fun <T, R> Collection<T>.memoryOptimizedZip(other: Collection<R>): List<Pa
 }
 
 /**
- * [Sequence] variant of [org.jetbrains.kotlin.backend.common.atMostOne]
+ * [Sequence] variant of [org.jetbrains.kotlin.utils.atMostOne]
+ *
  * So, when:
  * - there is no element then `null` will be returned
  * - there is a single element then the element will be returned
  * - there is more than one element then the error will be thrown
- * @see org.jetbrains.kotlin.backend.common.atMostOne
+ * @see org.jetbrains.kotlin.utils.atMostOne
  */
 fun <T> Sequence<T>.atMostOne(): T? {
     val iterator = iterator()
@@ -143,4 +144,4 @@ inline fun <reified T> Iterable<*>.findIsInstanceAnd(predicate: (T) -> Boolean):
  * The same as [Collection.toMutableList] extension function, but it returns a SmartList which is better with in sense of memory consumption
  * @see Collection.toMutableList
  */
-fun <T> Collection<T>.toSmartList(): List<T> = SmartList<T>(this)
+fun <T> Collection<T>.toSmartList(): List<T> = SmartList<T>(this)

kotlin-native/backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/DependenciesTracker.kt

@@ -5,7 +5,7 @@
 
 package org.jetbrains.kotlin.backend.konan
 
-import org.jetbrains.kotlin.backend.common.atMostOne
+import org.jetbrains.kotlin.utils.atMostOne
 import org.jetbrains.kotlin.backend.konan.descriptors.isInteropLibrary
 import org.jetbrains.kotlin.backend.konan.ir.isFromInteropLibrary
 import org.jetbrains.kotlin.backend.konan.llvm.FunctionOrigin

kotlin-native/backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/InlineClasses.kt

@@ -5,7 +5,7 @@
 
 package org.jetbrains.kotlin.backend.konan
 
-import org.jetbrains.kotlin.backend.common.atMostOne
+import org.jetbrains.kotlin.utils.atMostOne
 import org.jetbrains.kotlin.backend.konan.descriptors.findPackage
 import org.jetbrains.kotlin.backend.konan.ir.getSuperClassNotAny
 import org.jetbrains.kotlin.builtins.PrimitiveType

kotlin-native/backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/descriptors/DescriptorUtils.kt

@@ -5,7 +5,7 @@
 
 package org.jetbrains.kotlin.backend.konan.descriptors
 
-import org.jetbrains.kotlin.backend.common.atMostOne
+import org.jetbrains.kotlin.utils.atMostOne
 import org.jetbrains.kotlin.backend.konan.*
 import org.jetbrains.kotlin.backend.konan.ir.getSuperClassNotAny
 import org.jetbrains.kotlin.backend.konan.ir.getSuperInterfaces

kotlin-native/backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/descriptors/LegacyDescriptorUtils.kt

@@ -5,7 +5,7 @@
 
 package org.jetbrains.kotlin.backend.konan.descriptors
 
-import org.jetbrains.kotlin.backend.common.atMostOne
+import org.jetbrains.kotlin.utils.atMostOne
 import org.jetbrains.kotlin.backend.konan.RuntimeNames
 import org.jetbrains.kotlin.builtins.konan.KonanBuiltIns
 import org.jetbrains.kotlin.descriptors.*

kotlin-native/backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/ir/NewIrUtils.kt

@@ -5,7 +5,7 @@
 
 package org.jetbrains.kotlin.backend.konan.ir
 
-import org.jetbrains.kotlin.backend.common.atMostOne
+import org.jetbrains.kotlin.utils.atMostOne
 import org.jetbrains.kotlin.backend.konan.DECLARATION_ORIGIN_INLINE_CLASS_SPECIAL_FUNCTION
 import org.jetbrains.kotlin.backend.konan.descriptors.allOverriddenFunctions
 import org.jetbrains.kotlin.backend.konan.descriptors.isFromInteropLibrary

kotlin-native/backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/lower/Autoboxing.kt

@@ -7,7 +7,7 @@ package org.jetbrains.kotlin.backend.konan.lower
 
 import org.jetbrains.kotlin.backend.common.AbstractValueUsageTransformer
 import org.jetbrains.kotlin.backend.common.FileLoweringPass
-import org.jetbrains.kotlin.backend.common.atMostOne
+import org.jetbrains.kotlin.utils.atMostOne
 import org.jetbrains.kotlin.backend.common.getOrPut
 import org.jetbrains.kotlin.backend.common.lower.*
 import org.jetbrains.kotlin.backend.konan.*

kotlin-native/backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/lower/BuiltinOperatorLowering.kt

@@ -6,7 +6,7 @@
 package org.jetbrains.kotlin.backend.konan.lower
 
 import org.jetbrains.kotlin.backend.common.FileLoweringPass
-import org.jetbrains.kotlin.backend.common.atMostOne
+import org.jetbrains.kotlin.utils.atMostOne
 import org.jetbrains.kotlin.backend.common.lower.IrBuildingTransformer
 import org.jetbrains.kotlin.backend.common.lower.at
 import org.jetbrains.kotlin.backend.common.lower.irNot

kotlin-native/backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/optimizations/EscapeAnalysis.kt

@@ -5,7 +5,7 @@
 
 package org.jetbrains.kotlin.backend.konan.optimizations
 
-import org.jetbrains.kotlin.backend.common.atMostOne
+import org.jetbrains.kotlin.utils.atMostOne
 import org.jetbrains.kotlin.backend.common.peek
 import org.jetbrains.kotlin.backend.common.pop
 import org.jetbrains.kotlin.backend.common.push