From f08a7f14e043ce6fce7fb44119cd26ade2cf72a2 Mon Sep 17 00:00:00 2001
From: Dmitry Jemerov <yole@jetbrains.com>
Date: Tue, 9 Aug 2016 20:32:22 +0200
Subject: [PATCH] workaround for IDEA's issue that throws an exception when
 using union() on a LocalSearchScope with no elements (EA-82063 - AIOOBE:
 GlobalSearchScope.union)

---
 .../search/ideaExtensions/KotlinReferencesSearcher.kt  |  3 ++-
 .../src/org/jetbrains/kotlin/idea/search/searchUtil.kt | 10 ++++++++++
 2 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/idea/idea-analysis/src/org/jetbrains/kotlin/idea/search/ideaExtensions/KotlinReferencesSearcher.kt b/idea/idea-analysis/src/org/jetbrains/kotlin/idea/search/ideaExtensions/KotlinReferencesSearcher.kt
index 6d4b7aa1315..f8578a36150 100644
--- a/idea/idea-analysis/src/org/jetbrains/kotlin/idea/search/ideaExtensions/KotlinReferencesSearcher.kt
+++ b/idea/idea-analysis/src/org/jetbrains/kotlin/idea/search/ideaExtensions/KotlinReferencesSearcher.kt
@@ -36,6 +36,7 @@ import org.jetbrains.kotlin.idea.references.KtSimpleNameReference
 import org.jetbrains.kotlin.idea.search.KOTLIN_NAMED_ARGUMENT_SEARCH_CONTEXT
 import org.jetbrains.kotlin.idea.search.allScope
 import org.jetbrains.kotlin.idea.search.effectiveSearchScope
+import org.jetbrains.kotlin.idea.search.unionSafe
 import org.jetbrains.kotlin.idea.search.usagesSearch.dataClassComponentFunction
 import org.jetbrains.kotlin.idea.search.usagesSearch.getClassNameForCompanionObject
 import org.jetbrains.kotlin.idea.search.usagesSearch.getSpecialNamesToSearch
@@ -80,7 +81,7 @@ class KotlinReferencesSearcher : QueryExecutorBase<PsiReference, ReferencesSearc
 
         val effectiveSearchScope = runReadAction {
             val elements = if (unwrappedElement is KtDeclaration) unwrappedElement.toLightElements() else listOf(unwrappedElement)
-            elements.fold(queryParameters.effectiveSearchScope) { scope, e -> scope.union(queryParameters.effectiveSearchScope(e)) }
+            elements.fold(queryParameters.effectiveSearchScope) { scope, e -> scope.unionSafe(queryParameters.effectiveSearchScope(e)) }
         }
 
         val refFilter: (PsiReference) -> Boolean = when {
diff --git a/idea/idea-analysis/src/org/jetbrains/kotlin/idea/search/searchUtil.kt b/idea/idea-analysis/src/org/jetbrains/kotlin/idea/search/searchUtil.kt
index bec4b78a7b0..0142f17d822 100644
--- a/idea/idea-analysis/src/org/jetbrains/kotlin/idea/search/searchUtil.kt
+++ b/idea/idea-analysis/src/org/jetbrains/kotlin/idea/search/searchUtil.kt
@@ -32,6 +32,16 @@ infix fun SearchScope.or(otherScope: SearchScope): SearchScope = union(otherScop
 operator fun SearchScope.minus(otherScope: GlobalSearchScope): SearchScope = this and !otherScope
 operator fun GlobalSearchScope.not(): GlobalSearchScope = GlobalSearchScope.notScope(this)
 
+fun SearchScope.unionSafe(other: SearchScope): SearchScope {
+    if (this is LocalSearchScope && this.scope.isEmpty()) {
+        return other
+    }
+    if (other is LocalSearchScope && other.scope.isEmpty()) {
+        return this
+    }
+    return this.union(other)
+}
+
 fun Project.allScope(): GlobalSearchScope = GlobalSearchScope.allScope(this)
 
 fun Project.projectScope(): GlobalSearchScope = GlobalSearchScope.projectScope(this)