--- a/langtools/src/share/classes/com/sun/tools/javac/comp/Resolve.java	Fri Dec 06 09:07:47 2013 -0800
+++ b/langtools/src/share/classes/com/sun/tools/javac/comp/Resolve.java	Wed Dec 18 19:15:58 2013 +0000
@@ -1503,7 +1503,7 @@
             return ambiguityError(m1, m2);
         case AMBIGUOUS:
             //check if m1 is more specific than all ambiguous methods in m2
-            AmbiguityError e = (AmbiguityError)m2;
+            AmbiguityError e = (AmbiguityError)m2.baseSymbol();
             for (Symbol s : e.ambiguousSyms) {
                 if (mostSpecific(argtypes, m1, s, env, site, allowBoxing, useVarargs) != m1) {
                     return e.addAmbiguousSymbol(m1);
@@ -3055,7 +3055,7 @@
         final Symbol lookup(Env<AttrContext> env, MethodResolutionPhase phase) {
             Symbol sym = doLookup(env, phase);
             if (sym.kind == AMBIGUOUS) {
-                AmbiguityError a_err = (AmbiguityError)sym;
+                AmbiguityError a_err = (AmbiguityError)sym.baseSymbol();
                 sym = a_err.mergeAbstracts(site);
             }
             return sym;
@@ -3125,7 +3125,7 @@
 
         Symbol access(Env<AttrContext> env, DiagnosticPosition pos, Symbol location, Symbol sym) {
             if (sym.kind == AMBIGUOUS) {
-                AmbiguityError a_err = (AmbiguityError)sym;
+                AmbiguityError a_err = (AmbiguityError)sym.baseSymbol();
                 sym = a_err.mergeAbstracts(site);
             }
             //skip error reporting
@@ -3992,7 +3992,7 @@
 
         private List<Symbol> flatten(Symbol sym) {
             if (sym.kind == AMBIGUOUS) {
-                return ((AmbiguityError)sym).ambiguousSyms;
+                return ((AmbiguityError)sym.baseSymbol()).ambiguousSyms;
             } else {
                 return List.of(sym);
             }

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/langtools/test/tools/javac/T8029569/VarargsAmbiguityCrashTest.java	Wed Dec 18 19:15:58 2013 +0000
@@ -0,0 +1,41 @@
+/*
+ * Copyright (c) 2013, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * @test
+ * @bug 8029569
+ * @summary internal javac cast exception when resolving varargs ambiguity
+ * @compile/fail/ref=VarargsAmbiguityCrashTest.out -XDrawDiagnostics VarargsAmbiguityCrashTest.java
+ */
+
+public class VarargsAmbiguityCrashTest {
+    void m1() {
+        m2(null, new Exception());
+    }
+
+    void m2(Long l) {}
+
+    void m2(Exception... exception) {}
+
+    void m2(Long l, Exception... exception) {}
+}

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/langtools/test/tools/javac/T8029569/VarargsAmbiguityCrashTest.out	Wed Dec 18 19:15:58 2013 +0000
@@ -0,0 +1,2 @@
+VarargsAmbiguityCrashTest.java:33:9: compiler.err.ref.ambiguous: m2, kindname.method, m2(java.lang.Exception...), VarargsAmbiguityCrashTest, kindname.method, m2(java.lang.Long,java.lang.Exception...), VarargsAmbiguityCrashTest
+1 error