Result unused: a few enhancements for PSI checks

Related to KT-15063, KT-24433

idea/idea-analysis/src/org/jetbrains/kotlin/idea/inspections/AbstractResultUnusedChecker.kt

@@ -21,11 +21,14 @@ abstract class AbstractResultUnusedChecker(
     protected fun check(expression: KtExpression): Boolean {
         // Check whatever possible by PSI
         if (!expressionChecker(expression, this)) return false
+        var current: PsiElement? = expression
         var parent: PsiElement? = expression.parent
         while (parent != null) {
             if (parent is KtBlockExpression || parent is KtFunction || parent is KtFile) break
-            if (parent is KtValueArgument) return false
+            if (parent is KtValueArgument || parent is KtBinaryExpression || parent is KtUnaryExpression) return false
-            if (parent is KtBinaryExpression && parent.operationToken in KtTokens.ALL_ASSIGNMENTS) return false
+            if (parent is KtQualifiedExpression && parent.receiverExpression == current) return false
+            // TODO: add when condition, if condition (later when it's applicable not only to Deferred)
+            current = parent
             parent = parent.parent
         }
         // Then check by call

idea/testData/inspections/coroutines/asyncResultUnused/simple.kt

@@ -52,3 +52,10 @@ fun DbHandler.test() {
     doStuff().await()
 }
 
+operator fun Deferred<Int>.unaryPlus() = this
+operator fun Deferred<Int>.plus(arg: Int) = this
+
+fun moreFalsePositives() {
+    +(async { 0 })
+    async { -1 } + 1
+}