Minor

idea/idea-completion/src/org/jetbrains/kotlin/idea/completion/ExpectedInfos.kt

@@ -22,7 +22,6 @@ import org.jetbrains.kotlin.descriptors.*
 import org.jetbrains.kotlin.frontend.di.createContainerForMacros
 import org.jetbrains.kotlin.idea.caches.resolve.ResolutionFacade
 import org.jetbrains.kotlin.idea.completion.smart.TypesWithContainsDetector
-import org.jetbrains.kotlin.idea.completion.smart.toList
 import org.jetbrains.kotlin.idea.core.IterableTypesDetector
 import org.jetbrains.kotlin.idea.core.mapArgumentsToParameters
 import org.jetbrains.kotlin.idea.util.FuzzyType
@@ -53,6 +52,7 @@ import org.jetbrains.kotlin.types.expressions.ExpressionTypingUtils
 import org.jetbrains.kotlin.types.typeUtil.containsError
 import org.jetbrains.kotlin.types.typeUtil.makeNotNullable
 import org.jetbrains.kotlin.utils.addToStdlib.check
+import org.jetbrains.kotlin.utils.addToStdlib.singletonOrEmptyList
 import java.util.LinkedHashSet
 
 enum class Tail {
@@ -440,13 +440,13 @@ class ExpectedInfos(
         val declaration = expressionWithType.getParent() as? JetDeclarationWithBody ?: return null
         if (expressionWithType != declaration.getBodyExpression() || declaration.hasBlockBody()) return null
         val descriptor = bindingContext[BindingContext.DECLARATION_TO_DESCRIPTOR, declaration] as? FunctionDescriptor ?: return null
-        return functionReturnValueExpectedInfo(descriptor, expectType = declaration.hasDeclaredReturnType()).toList()
+        return functionReturnValueExpectedInfo(descriptor, expectType = declaration.hasDeclaredReturnType()).singletonOrEmptyList()
     }
 
     private fun calculateForReturn(expressionWithType: JetExpression): Collection<ExpectedInfo>? {
         val returnExpression = expressionWithType.getParent() as? JetReturnExpression ?: return null
         val descriptor = returnExpression.getTargetFunctionDescriptor(bindingContext) ?: return null
-        return functionReturnValueExpectedInfo(descriptor, expectType = true).toList()
+        return functionReturnValueExpectedInfo(descriptor, expectType = true).singletonOrEmptyList()
     }
 
     private fun functionReturnValueExpectedInfo(descriptor: FunctionDescriptor, expectType: Boolean): ReturnValueExpectedInfo? {

idea/idea-completion/src/org/jetbrains/kotlin/idea/completion/smart/SmartCompletion.kt

@@ -42,6 +42,7 @@ import org.jetbrains.kotlin.resolve.DescriptorUtils
 import org.jetbrains.kotlin.types.JetType
 import org.jetbrains.kotlin.types.TypeUtils
 import org.jetbrains.kotlin.types.typeUtil.makeNotNullable
+import org.jetbrains.kotlin.utils.addToStdlib.singletonOrEmptySet
 import java.util.ArrayList
 import java.util.HashSet
 
@@ -237,7 +238,7 @@ class SmartCompletion(
                     if (operationToken == JetTokens.EQ || operationToken in COMPARISON_TOKENS) {
                         val left = parent.getLeft()
                         if (left is JetReferenceExpression) {
-                            return bindingContext[BindingContext.REFERENCE_TARGET, left].toSet()
+                            return bindingContext[BindingContext.REFERENCE_TARGET, left].singletonOrEmptySet()
                         }
                     }
                 }

idea/idea-completion/src/org/jetbrains/kotlin/idea/completion/smart/Utils.kt

@@ -27,7 +27,6 @@ import org.jetbrains.kotlin.descriptors.impl.LocalVariableDescriptor
 import org.jetbrains.kotlin.idea.completion.*
 import org.jetbrains.kotlin.idea.completion.handlers.WithExpressionPrefixInsertHandler
 import org.jetbrains.kotlin.idea.completion.handlers.WithTailInsertHandler
-import org.jetbrains.kotlin.idea.completion.SmartCastCalculator
 import org.jetbrains.kotlin.idea.util.*
 import org.jetbrains.kotlin.psi.JetExpression
 import org.jetbrains.kotlin.psi.JetSimpleNameExpression
@@ -297,9 +296,6 @@ fun LookupElementFactory.createLookupElement(
     return element
 }
 
-fun <T : Any> T?.toList(): List<T> = if (this != null) listOf(this) else listOf()
-fun <T : Any> T?.toSet(): Set<T> = if (this != null) setOf(this) else setOf()
-
 enum class SmartCompletionItemPriority {
     IT,
     TRUE,