Rename: Allow deleting name of companion object

#KT-20178 Fixed

idea/idea-analysis/src/org/jetbrains/kotlin/idea/references/KtSimpleNameReference.kt

@@ -28,10 +28,7 @@ import org.jetbrains.kotlin.idea.caches.resolve.analyze
 import org.jetbrains.kotlin.idea.caches.resolve.resolveImportReference
 import org.jetbrains.kotlin.idea.codeInsight.shorten.addDelayedImportRequest
 import org.jetbrains.kotlin.idea.codeInsight.shorten.addToShorteningWaitSet
-import org.jetbrains.kotlin.idea.core.ShortenReferences
-import org.jetbrains.kotlin.idea.core.copied
-import org.jetbrains.kotlin.idea.core.quoteIfNeeded
-import org.jetbrains.kotlin.idea.core.replaced
+import org.jetbrains.kotlin.idea.core.*
 import org.jetbrains.kotlin.idea.intentions.OperatorToFunctionIntention
 import org.jetbrains.kotlin.idea.refactoring.fqName.getKotlinFqName
 import org.jetbrains.kotlin.lexer.KtToken
@@ -39,6 +36,7 @@ import org.jetbrains.kotlin.lexer.KtTokens
 import org.jetbrains.kotlin.load.java.descriptors.JavaPropertyDescriptor
 import org.jetbrains.kotlin.name.FqName
 import org.jetbrains.kotlin.name.Name
+import org.jetbrains.kotlin.name.SpecialNames
 import org.jetbrains.kotlin.name.isOneSegmentFQN
 import org.jetbrains.kotlin.plugin.references.SimpleNameReferenceExtension
 import org.jetbrains.kotlin.psi.*
@@ -108,6 +106,20 @@ class KtSimpleNameReference(expression: KtSimpleNameExpression) : KtSimpleRefere
         if (!canRename()) throw IncorrectOperationException()
         if (newElementName == null) return expression
 
+        if (newElementName.unquote() == "") {
+            val qualifiedElement = expression.getQualifiedElement()
+            return when (qualifiedElement) {
+                is KtQualifiedExpression -> {
+                    expression.replace(qualifiedElement.receiverExpression)
+                    qualifiedElement.replaced(qualifiedElement.selectorExpression!!)
+                }
+                is KtUserType -> {
+                    expression.replaced(KtPsiFactory(expression).createSimpleName(SpecialNames.DEFAULT_NAME_FOR_COMPANION_OBJECT.asString()))
+                }
+                else -> expression
+            }
+        }
+
         // Do not rename if the reference corresponds to synthesized component function
         val expressionText = expression.text
         if (expressionText != null && Name.isValidIdentifier(expressionText)) {