Cleanup: apply "Convert lambda to reference"

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

@@ -42,7 +42,7 @@ abstract class DeclarationLookupObjectImpl(
             return if (descriptor != null)
                 descriptor.importableFqName
             else
-                (psiElement as? PsiClass)?.qualifiedName?.let { FqName(it) }
+                (psiElement as? PsiClass)?.qualifiedName?.let(::FqName)
         }
 
     override fun toString() = super.toString() + " " + (descriptor ?: psiElement)

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

@@ -111,7 +111,7 @@ class InsertHandlerProvider(
             }
         }
 
-        originalFunction.extensionReceiverParameter?.type?.let { addPotentiallyInferred(it) }
+        originalFunction.extensionReceiverParameter?.type?.let(::addPotentiallyInferred)
         originalFunction.valueParameters.forEach { addPotentiallyInferred(it.type) }
 
         fun allTypeParametersPotentiallyInferred() = originalFunction.typeParameters.all { it in potentiallyInferred }

idea/idea-completion/src/org/jetbrains/kotlin/idea/completion/handlers/handlerUtils.kt

@@ -153,7 +153,7 @@ fun createKeywordConstructLookupElement(
 private fun detectIndent(text: CharSequence, offset: Int): String {
     return text.substring(0, offset)
             .substringAfterLast('\n')
-            .takeWhile { it.isWhitespace() }
+            .takeWhile(Char::isWhitespace)
 }
 
 private fun String.indentLinesAfterFirst(indent: String): String {

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

@@ -412,7 +412,7 @@ class SmartCompletion(
                 if (descriptor.modality != Modality.ABSTRACT && !descriptor.isInner) {
                     descriptor.constructors
                             .filter(visibilityFilter)
-                            .mapNotNullTo(this) { toLookupElement(it) }
+                            .mapNotNullTo(this, ::toLookupElement)
                 }
             }
         }