7040104: javac NPE on Object a[]; Object o = (a=null)[0];

When a null literal is found on top of stack, if expected type is 1-dimension array no checkcast is emitted

Reviewed-by: jjg

langtools/src/share/classes/com/sun/tools/javac/jvm/Code.java

@@ -479,7 +479,12 @@ public class Code {
             state.pop(1);// index
             Type a = state.stack[state.stacksize-1];
             state.pop(1);
-            state.push(types.erasure(types.elemtype(a))); }
+            //sometimes 'null type' is treated as a one-dimensional array type
+            //see Gen.visitLiteral - we should handle this case accordingly
+            Type stackType = a.tag == BOT ?
+                syms.objectType :
+                types.erasure(types.elemtype(a));
+            state.push(stackType); }
             break;
         case goto_:
             markDead();

langtools/test/tools/javac/T7040104.java

@@ -0,0 +1,72 @@
+/*
+ * 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 7040104
+ * @summary javac NPE on Object a[]; Object o = (a=null)[0];
+ */
+
+public class T7040104 {
+    public static void main(String[] args) {
+        T7040104 t = new T7040104();
+        t.test1();
+        t.test2();
+        t.test3();
+        if (t.npeCount != 3) {
+            throw new AssertionError();
+        }
+    }
+
+    int npeCount = 0;
+
+    void test1() {
+        Object a[];
+        try {
+            Object o = (a = null)[0];
+        }
+        catch (NullPointerException npe) {
+            npeCount++;
+        }
+    }
+
+    void test2() {
+        Object a[][];
+        try {
+            Object o = (a = null)[0][0];
+        }
+        catch (NullPointerException npe) {
+            npeCount++;
+        }
+    }
+
+    void test3() {
+        Object a[][][];
+        try {
+            Object o = (a = null)[0][0][0];
+        }
+        catch (NullPointerException npe) {
+            npeCount++;
+        }
+    }
+}