From 4d4a45f79a2f6fb5311b15f3f387527bf830a1db Mon Sep 17 00:00:00 2001
From: Andrey Breslav <abreslav@abreslav-mac.labs.intellij.net>
Date: Tue, 20 Dec 2011 14:21:45 +0400
Subject: [PATCH] KT-860 ConcurrentModificationException in frontend

---
 .../inference/ConstraintSystemWithPriorities.java  |  2 +-
 .../diagnostics/tests/regressions/kt860.jet        | 14 ++++++++++++++
 2 files changed, 15 insertions(+), 1 deletion(-)
 create mode 100644 compiler/testData/diagnostics/tests/regressions/kt860.jet

diff --git a/compiler/frontend/src/org/jetbrains/jet/lang/resolve/calls/inference/ConstraintSystemWithPriorities.java b/compiler/frontend/src/org/jetbrains/jet/lang/resolve/calls/inference/ConstraintSystemWithPriorities.java
index 3da752a9950..270e5804ff3 100644
--- a/compiler/frontend/src/org/jetbrains/jet/lang/resolve/calls/inference/ConstraintSystemWithPriorities.java
+++ b/compiler/frontend/src/org/jetbrains/jet/lang/resolve/calls/inference/ConstraintSystemWithPriorities.java
@@ -259,7 +259,7 @@ public class ConstraintSystemWithPriorities implements ConstraintSystem {
 
         assert constraintQueue.isEmpty() || unsolvedUnknowns.isEmpty() : constraintQueue + " " + unsolvedUnknowns;
 
-        for (TypeValue unknown : unsolvedUnknowns) {
+        for (TypeValue unknown : Sets.newLinkedHashSet(unsolvedUnknowns)) {
             if (!computeValueFor(unknown)) {
                 listener.error("Not enough data to compute value for ", unknown);
                 solution.registerError("Not enough data to compute value for " + unknown + ". Please, specify type arguments explicitly");
diff --git a/compiler/testData/diagnostics/tests/regressions/kt860.jet b/compiler/testData/diagnostics/tests/regressions/kt860.jet
new file mode 100644
index 00000000000..d8acf4fad50
--- /dev/null
+++ b/compiler/testData/diagnostics/tests/regressions/kt860.jet
@@ -0,0 +1,14 @@
+// KT-860 ConcurrentModificationException in frontend
+// +JDK
+
+namespace std.util
+
+import java.util.*
+
+fun <T, U: Collection<in T>> Iterator<T>.to(container: U) : U {
+    while(hasNext)
+        container.add(next())
+    return container
+}
+
+inline fun <T> Iterator<T>.toArrayList() = to(ArrayList<T>())