if child is already resolved/rejected — no need to notify it

platform/projectModel-api/src/org/jetbrains/concurrency/AsyncPromise.kt

@@ -1,5 +1,5 @@
 /*
- * Copyright 2000-2016 JetBrains s.r.o.
+ * Copyright 2000-2017 JetBrains s.r.o.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -78,6 +78,10 @@ open class AsyncPromise<T> : Promise<T>, Getter<T> {
   override fun notify(child: AsyncPromise<in T>) {
     LOG.assertTrue(child !== this)
 
+    if (child.state != State.PENDING) {
+      return
+    }
+
     when (state) {
       State.PENDING -> {
         addHandlers(Consumer({ child.catchError { child.setResult(it) } }), Consumer({ child.setError(it) }))