KT-14241 Add Intention + Inspection to remove empty class body (#968)

idea/src/META-INF/plugin.xml

@@ -1390,6 +1390,11 @@
       <category>Kotlin</category>
     </intentionAction>
 
+    <intentionAction>
+      <className>org.jetbrains.kotlin.idea.intentions.RemoveEmptyClassBodyIntention</className>
+      <category>Kotlin</category>
+    </intentionAction>
+
     <localInspection implementationClass="org.jetbrains.kotlin.idea.intentions.ObjectLiteralToLambdaInspection"
                      displayName="Object literal can be converted to lambda"
                      groupName="Kotlin"
@@ -1847,6 +1852,15 @@
                      language="kotlin"
     />
 
+    <localInspection implementationClass="org.jetbrains.kotlin.idea.intentions.RemoveEmptyClassBodyInspection"
+                     displayName="Replace empty class body"
+                     groupName="Kotlin"
+                     enabledByDefault="true"
+                     cleanupTool="true"
+                     level="INFO"
+                     language="kotlin"
+    />
+
     <referenceImporter implementation="org.jetbrains.kotlin.idea.quickfix.KotlinReferenceImporter"/>
 
     <fileType.fileViewProviderFactory filetype="KJSM" implementationClass="com.intellij.psi.ClassFileViewProviderFactory"/>

idea/src/org/jetbrains/kotlin/idea/intentions/RemoveEmptyClassBodyIntention.kt

@@ -0,0 +1,34 @@
+/*
+ * Copyright 2010-2016 JetBrains s.r.o.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.jetbrains.kotlin.idea.intentions
+
+import com.intellij.codeInspection.CleanupLocalInspectionTool
+import com.intellij.codeInspection.ProblemHighlightType
+import com.intellij.openapi.editor.Editor
+import org.jetbrains.kotlin.idea.inspections.IntentionBasedInspection
+import org.jetbrains.kotlin.psi.KtClassBody
+
+class RemoveEmptyClassBodyInspection : IntentionBasedInspection<KtClassBody>(RemoveEmptyClassBodyIntention::class), CleanupLocalInspectionTool {
+    override val problemHighlightType: ProblemHighlightType
+        get() = ProblemHighlightType.LIKE_UNUSED_SYMBOL
+}
+
+class RemoveEmptyClassBodyIntention : SelfTargetingOffsetIndependentIntention<KtClassBody>(KtClassBody::class.java, "Remove empty class body") {
+    override fun applyTo(element: KtClassBody, editor: Editor?) = element.delete()
+
+    override fun isApplicableTo(element: KtClassBody) = element.text.replace("{", "").replace("}", "").isBlank()
+}