Fix hint text for replace with operator assignment #KT-23559 Fixed

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

@@ -55,7 +55,7 @@ class ReplaceWithOperatorAssignmentInspection : AbstractApplicabilityBasedInspec
     override val defaultFixText = "Replace with operator-assignment"
 
     override fun fixText(element: KtBinaryExpression) =
-            "Replace with '${element.operationReference.operationSignTokenType?.value}='"
+        "Replace with '${(element.right as? KtBinaryExpression)?.operationReference?.operationSignTokenType?.value}='"
 
     private fun checkExpressionRepeat(variableExpression: KtNameReferenceExpression, expression: KtBinaryExpression, bindingContext: BindingContext): Boolean {
         val descriptor = bindingContext[BindingContext.REFERENCE_TARGET, expression.operationReference]?.containingDeclaration

idea/testData/inspectionsLocal/replaceWithOperatorAssignment/validAddition.kt

@@ -0,0 +1,5 @@
+// FIX: Replace with '+='
+fun foo() {
+    var x = 0
+    <caret>x = x + 1
+}

idea/testData/inspectionsLocal/replaceWithOperatorAssignment/validAddition.kt.after

@@ -0,0 +1,5 @@
+// FIX: Replace with '+='
+fun foo() {
+    var x = 0
+    x += 1
+}

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

@@ -3977,6 +3977,11 @@ public class LocalInspectionTestGenerated extends AbstractLocalInspectionTest {
             runTest("idea/testData/inspectionsLocal/replaceWithOperatorAssignment/simpleAssign.kt");
         }
 
+        @TestMetadata("validAddition.kt")
+        public void testValidAddition() throws Exception {
+            runTest("idea/testData/inspectionsLocal/replaceWithOperatorAssignment/validAddition.kt");
+        }
+
         @TestMetadata("validSubtraction.kt")
         public void testValidSubtraction() throws Exception {
             runTest("idea/testData/inspectionsLocal/replaceWithOperatorAssignment/validSubtraction.kt");