Assign backing field: don't add empty line

#KT-28694 Fixed

idea/src/org/jetbrains/kotlin/idea/inspections/SetterBackingFieldAssignmentInspection.kt

@@ -8,12 +8,14 @@ package org.jetbrains.kotlin.idea.inspections
 import com.intellij.codeInspection.*
 import com.intellij.openapi.project.Project
 import com.intellij.psi.PsiElementVisitor
+import com.intellij.psi.PsiWhiteSpace
 import org.jetbrains.kotlin.descriptors.PropertyDescriptor
 import org.jetbrains.kotlin.descriptors.ValueParameterDescriptor
 import org.jetbrains.kotlin.idea.caches.resolve.analyze
 import org.jetbrains.kotlin.lexer.KtTokens
 import org.jetbrains.kotlin.psi.*
 import org.jetbrains.kotlin.psi.psiUtil.anyDescendantOfType
+import org.jetbrains.kotlin.psi.psiUtil.siblings
 import org.jetbrains.kotlin.resolve.BindingContext
 import org.jetbrains.kotlin.resolve.calls.callUtil.getResolvedCall
 
@@ -69,7 +71,7 @@ private val assignmentOperators = listOf(KtTokens.EQ, KtTokens.PLUSEQ, KtTokens.
 private val incrementAndDecrementOperators = listOf(KtTokens.PLUSPLUS, KtTokens.MINUSMINUS)
 
 private class AssignBackingFieldFix : LocalQuickFix {
-    override fun getName() = "Assign backing filed"
+    override fun getName() = "Assign backing field"
 
     override fun getFamilyName() = name
 
@@ -77,10 +79,11 @@ private class AssignBackingFieldFix : LocalQuickFix {
         val setter = descriptor.psiElement as? KtPropertyAccessor ?: return
         val parameter = setter.valueParameters.firstOrNull() ?: return
         val bodyExpression = setter.bodyBlockExpression ?: return
-        setter.hasBlockBody()
+        bodyExpression.lBrace
-        bodyExpression.addBefore(
+            ?.siblings(withItself = false)
-            KtPsiFactory(setter).createExpression("field = ${parameter.text}"),
+            ?.takeWhile { it != bodyExpression.rBrace }
-            bodyExpression.rBrace
+            ?.singleOrNull { it is PsiWhiteSpace }
-        )
+            ?.also { it.delete() }
+        bodyExpression.addBefore(KtPsiFactory(setter).createExpression("field = ${parameter.text}"), bodyExpression.rBrace)
     }
 }

idea/testData/inspectionsLocal/setterBackingFieldAssignment/noAssignment.kt

@@ -1,3 +1,4 @@
+// FIX: Assign backing field
 class Test {
     var foo: Int = 1
         <caret>set(value) {

idea/testData/inspectionsLocal/setterBackingFieldAssignment/noAssignment.kt.after

@@ -1,3 +1,4 @@
+// FIX: Assign backing field
 class Test {
     var foo: Int = 1
         set(value) {

idea/testData/inspectionsLocal/setterBackingFieldAssignment/noAssignment3.kt

@@ -0,0 +1,6 @@
+class Test {
+    var foo: Int = 1
+        <caret>set(value) {
+
+        }
+}

idea/testData/inspectionsLocal/setterBackingFieldAssignment/noAssignment3.kt.after

@@ -0,0 +1,6 @@
+class Test {
+    var foo: Int = 1
+        set(value) {
+            field = value
+        }
+}

idea/tests/org/jetbrains/kotlin/idea/inspections/LocalInspectionTestGenerated.java

@@ -6354,6 +6354,11 @@ public class LocalInspectionTestGenerated extends AbstractLocalInspectionTest {
             runTest("idea/testData/inspectionsLocal/setterBackingFieldAssignment/noAssignment2.kt");
         }
 
+        @TestMetadata("noAssignment3.kt")
+        public void testNoAssignment3() throws Exception {
+            runTest("idea/testData/inspectionsLocal/setterBackingFieldAssignment/noAssignment3.kt");
+        }
+
         @TestMetadata("noBackingField.kt")
         public void testNoBackingField() throws Exception {
             runTest("idea/testData/inspectionsLocal/setterBackingFieldAssignment/noBackingField.kt");