--- a/langtools/src/share/classes/com/sun/tools/javac/jvm/CRTable.java	Fri Nov 02 14:35:57 2012 -0700
+++ b/langtools/src/share/classes/com/sun/tools/javac/jvm/CRTable.java	Fri Nov 02 19:17:03 2012 -0700
@@ -503,6 +503,14 @@
             result = sr;
         }
 
+        @Override
+        public void visitLetExpr(LetExpr tree) {
+            SourceRange sr = new SourceRange(startPos(tree), endPos(tree));
+            sr.mergeWith(csp(tree.defs));
+            sr.mergeWith(csp(tree.expr));
+            result = sr;
+        }
+
         public void visitTypeParameter(JCTypeParameter tree) {
             SourceRange sr = new SourceRange(startPos(tree), endPos(tree));
             sr.mergeWith(csp(tree.bounds));
@@ -525,7 +533,7 @@
          */
         public int startPos(JCTree tree) {
             if (tree == null) return Position.NOPOS;
-            return tree.pos;
+            return TreeInfo.getStartPos(tree);
         }
 
         /** The end position of given tree, if it has
@@ -533,9 +541,7 @@
          */
         public int endPos(JCTree tree) {
             if (tree == null) return Position.NOPOS;
-            if (tree.hasTag(JCTree.Tag.BLOCK))
-                return ((JCBlock) tree).endpos;
-            return endPosTable.getEndPos(tree);
+            return TreeInfo.getEndPos(tree, endPosTable);
         }
     }
 

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/langtools/test/tools/javac/options/T6949443.java	Fri Nov 02 19:17:03 2012 -0700
@@ -0,0 +1,36 @@
+/*
+ * Copyright (c) 2010, 2012, 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 6949443
+ * @summary VisitTree assertion triggered using -Xjcov on small sample program
+ * @compile -Xjcov T6949443.java
+ */
+
+public class T6949443 {
+    public static void main(String[] args) {
+        Integer i = 0;
+        i++;
+    }
+}