Refactoring: "replace with operator assignment" is now an inspection

idea/testData/inspectionsLocal/replaceWithOperatorAssignment/plusAssignConflict.kt

@@ -0,0 +1,11 @@
+// PROBLEM: none
+class A
+
+operator fun A.plus(a: A): A = A()
+operator fun A.plusAssign(a: A){}
+
+fun foo() {
+    var a1 = A()
+    val a2 = A()
+    a1 <caret>= a1 + a2
+}