Add intention to convert top level val with object expression to object declaration (#974)

* Add intention to convert top level val with object expression to object
Fixes #KT-14137

* fix intention description

idea/src/META-INF/plugin.xml

@@ -1574,6 +1574,11 @@
       <category>Kotlin</category>
     </intentionAction>
 
+    <intentionAction>
+      <className>org.jetbrains.kotlin.idea.intentions.ValToObjectIntention</className>
+      <category>Kotlin</category>
+    </intentionAction>
+
     <localInspection implementationClass="org.jetbrains.kotlin.idea.intentions.ObjectLiteralToLambdaInspection"
                      displayName="Object literal can be converted to lambda"
                      groupName="Kotlin"

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

@@ -0,0 +1,59 @@
+/*
+ * Copyright 2010-2017 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.openapi.editor.Editor
+import com.intellij.psi.search.searches.ReferencesSearch
+import org.jetbrains.kotlin.idea.core.replaced
+import org.jetbrains.kotlin.idea.references.KtReference
+import org.jetbrains.kotlin.psi.*
+import org.jetbrains.kotlin.psi.psiUtil.endOffset
+import org.jetbrains.kotlin.psi.psiUtil.visibilityModifier
+
+class ValToObjectIntention : SelfTargetingIntention<KtProperty>(KtProperty::class.java, "Convert to object declaration") {
+
+    override fun isApplicableTo(element: KtProperty, caretOffset: Int): Boolean {
+        if (element.isVar) return false
+        if (!element.isTopLevel) return false
+
+        val initializer = element.initializer as? KtObjectLiteralExpression ?: return false
+        if (initializer.objectDeclaration.getBody() == null) return false
+
+        if (element.getter != null) return false
+        if (element.annotationEntries.isNotEmpty()) return false
+
+        // disable if has non-Kotlin usages
+        return ReferencesSearch.search(element).all { it is KtReference && it.element.parent !is KtCallableReferenceExpression }
+    }
+
+    override fun applyTo(element: KtProperty, editor: Editor?) {
+        val modifier = element.visibilityModifier()
+        val name = element.name ?: return
+        val objectLiteral = element.initializer as? KtObjectLiteralExpression ?: return
+        val declaration = objectLiteral.objectDeclaration
+        val superTypeList = declaration.getSuperTypeList()
+        val body = declaration.getBody() ?: return
+
+        val prefix = modifier?.text?.plus(" ") ?: ""
+        val superTypesText = superTypeList?.text?.plus(" ") ?: ""
+
+        val replacementText = "${prefix}object $name: $superTypesText${body.text}"
+        val replaced = element.replaced(KtPsiFactory(element).createDeclarationByPattern<KtObjectDeclaration>(replacementText))
+
+        editor?.caretModel?.moveToOffset(replaced.nameIdentifier?.endOffset ?: return)
+    }
+}