Add Smart Enter processor for object expessions (#1079)

Fixes #KT-17807

idea/src/org/jetbrains/kotlin/idea/editor/fixers/KotlinClassBodyFixer.kt

@@ -22,18 +22,26 @@ import com.intellij.psi.PsiElement
 import org.jetbrains.kotlin.idea.editor.KotlinSmartEnterHandler
 import org.jetbrains.kotlin.psi.KtClassOrObject
 import org.jetbrains.kotlin.psi.psiUtil.endOffset
+import org.jetbrains.kotlin.psi.psiUtil.getPrevSiblingIgnoringWhitespaceAndComments
 
 class KotlinClassBodyFixer : SmartEnterProcessorWithFixers.Fixer<KotlinSmartEnterHandler>() {
     override fun apply(editor: Editor, processor: KotlinSmartEnterHandler, psiElement: PsiElement) {
         if (psiElement !is KtClassOrObject) return
-        if (psiElement.getBody() != null) return
 
-        val doc = editor.document
+        val body = psiElement.getBody()
-        val endOffset = psiElement.range.end
+        if (!body?.text.isNullOrBlank()) return
 
-        editor.caretModel.moveToOffset(psiElement.endOffset - 1)
+        var endOffset = psiElement.range.end
+
+        if (body != null) {
+            body.getPrevSiblingIgnoringWhitespaceAndComments()?.let {
+                endOffset = it.endOffset
+            }
+        }
+
+        editor.caretModel.moveToOffset(endOffset - 1)
 
         // Insert '\n' to force a multiline body, otherwise there will be an empty body on one line and a caret on the next one.
-        doc.insertString(endOffset, "{\n}")
+        editor.document.insertString(endOffset, "{\n}")
     }
 }

idea/tests/org/jetbrains/kotlin/idea/codeInsight/smartEnter/SmartEnterTest.kt

@@ -1380,6 +1380,38 @@ class SmartEnterTest : KotlinLightCodeInsightFixtureTestCase() {
             """
     )
 
+    fun testObjectExpressionBody1() = doFileTest(
+            """
+            interface I
+            val a = object : I<caret>
+            """
+            ,
+            """
+            interface I
+            val a = object : I {
+                <caret>
+            }
+            """
+    )
+
+    fun testObjectExpressionBody2() = doFileTest(
+            """
+            interface I
+            val a = object : I<caret>
+
+            val b = ""
+            """
+            ,
+            """
+            interface I
+            val a = object : I {
+                <caret>
+            }
+
+            val b = ""
+            """
+    )
+
     fun doFunTest(before: String, after: String) {
         fun String.withFunContext(): String {
             val bodyText = "//----\n${this.trimIndent()}\n//----"