Introduce inspection "async result unused" #KT-24433 Fixed

idea/testData/inspections/coroutines/asyncResultUnused/inspectionData/expected.xml

@@ -0,0 +1,11 @@
+<problems>
+    <problem>
+        <file>simple.kt</file>
+        <line>30</line>
+        <module>light_idea_test_case</module>
+        <package>&lt;default&gt;</package>
+        <entry_point TYPE="file" FQNAME="temp:///src/simple.kt" />
+        <problem_class severity="WARNING" attribute_key="WARNING_ATTRIBUTES">Result of 'async' is not used</problem_class>
+        <description>Result of 'async' is never used</description>
+    </problem>
+</problems>

idea/testData/inspections/coroutines/asyncResultUnused/inspectionData/inspections.test

@@ -0,0 +1 @@
+// INSPECTION_CLASS: org.jetbrains.kotlin.idea.inspections.coroutines.AsyncResultUnusedInspection

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

@@ -0,0 +1,39 @@
+package kotlinx.coroutines.experimental
+
+interface Deferred<T> {
+    suspend fun await(): T
+}
+
+interface CoroutineContext
+
+object DefaultContext : CoroutineContext
+
+enum class CoroutineStart {
+    DEFAULT,
+    LAZY,
+    ATOMIC,
+    UNDISPATCHED
+}
+
+interface Job
+
+fun <T> async(
+    context: CoroutineContext = DefaultContext,
+    start: CoroutineStart = CoroutineStart.DEFAULT,
+    parent: Job? = null,
+    f: suspend () -> T
+): Deferred<T> {
+    TODO()
+}
+
+fun test() {
+    async { 42 }
+}
+
+fun useIt(d: Deferred<Int>) {}
+
+fun falsePositives() {
+    async { 3 }.await()
+    val res = async { 13 }
+    useIt(async { 7 })
+}