7013865: varargs: javac crashes during overload resolution with generic varargs

Summary: fixed regression with varargs overload resolution that leads javac to crash
Reviewed-by: jjg

src/share/classes/com/sun/tools/javac/comp/Infer.java

@@ -407,7 +407,9 @@ public class Infer {
 
         // for varargs arguments as well
         if (useVarargs) {
-            Type elemType = types.elemtype(varargsFormal);
+            //note: if applicability check is triggered by most specific test,
+            //the last argument of a varargs is _not_ an array type (see JLS 15.12.2.5)
+            Type elemType = types.elemtypeOrType(varargsFormal);
             Type elemUndet = types.subst(elemType, tvars, undetvars);
             while (actuals.nonEmpty()) {
                 Type actual = actuals.head.baseType();

test/tools/javac/varargs/T7013865.java

+/*
+ * Copyright (c) 2011, 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     7013865
+ * @summary varargs: javac crashes during overload resolution with generic varargs
+ * @compile T7013865.java
+ */
+
+class T7013865 {
+    public <X extends Number> void m(X... args) { }
+    public void m(Object... args) { }
+
+    { m(null, null); }
+}