diff --git a/js/js.tests/test/org/jetbrains/kotlin/js/test/utils/AmbiguousAstSourcePropagation.kt b/js/js.tests/test/org/jetbrains/kotlin/js/test/utils/AmbiguousAstSourcePropagation.kt
new file mode 100644
index 00000000000..9316e252089
--- /dev/null
+++ b/js/js.tests/test/org/jetbrains/kotlin/js/test/utils/AmbiguousAstSourcePropagation.kt
@@ -0,0 +1,79 @@
+/*
+ * Copyright 2010-2017 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.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.jetbrains.kotlin.js.test.utils
+
+import com.intellij.psi.PsiElement
+import org.jetbrains.kotlin.js.backend.ast.*
+
+class AmbiguousAstSourcePropagation : RecursiveJsVisitor() {
+    private var sourceDefined = false
+
+    override fun visitConditional(x: JsConditional) = acceptAll(x, x.testExpression, x.thenExpression, x.elseExpression)
+    
+    override fun visitBinaryExpression(x: JsBinaryOperation) = acceptAll(x, x.arg1, x.arg2)
+
+    override fun visitPostfixOperation(x: JsPostfixOperation) = acceptAll(x, x.arg)
+
+    override fun visitArrayAccess(x: JsArrayAccess) = acceptAll(x, x.arrayExpression, x.indexExpression)
+
+    override fun visitPropertyInitializer(x: JsPropertyInitializer) = acceptAll(x, x.labelExpr, x.valueExpr)
+
+    override fun visitInvocation(invocation: JsInvocation) = acceptAll(invocation, invocation.qualifier,
+                                                                       *invocation.arguments.toTypedArray())
+
+    override fun visitNameRef(nameRef: JsNameRef) {
+        val qualifier = nameRef.qualifier
+        if (qualifier != null) {
+            acceptAll(nameRef, qualifier)
+        }
+        else {
+            super.visitNameRef(nameRef)
+        }
+    }
+
+    override fun visitElement(node: JsNode) {
+        val old = sourceDefined
+        propagate(node)
+
+        sourceDefined = false
+        super.visitElement(node)
+        sourceDefined = old
+    }
+    
+    private fun acceptAll(node: JsNode, first: JsNode, vararg remaining: JsNode) {
+        val old = sourceDefined
+        propagate(node)
+        
+        accept(first)
+
+        sourceDefined = false
+        remaining.forEach { accept(it) }
+        sourceDefined = old
+    }
+
+    private fun propagate(node: JsNode) {
+        if (!sourceDefined) {
+            val source = node.source
+            if (source is JsLocation || source is PsiElement) {
+                sourceDefined = true
+            }
+        }
+        else if (node !is JsExpressionStatement) {
+            node.source = null
+        }
+    }
+}
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