1 files changed, 59 insertions, 0 deletions
diff --git a/tools/eslint/lib/rules/no-duplicate-case.js b/tools/eslint/lib/rules/no-duplicate-case.js
new file mode 100644
index 0000000000..89de7174fc
--- /dev/null
+++ b/tools/eslint/lib/rules/no-duplicate-case.js
@@ -0,0 +1,59 @@
+/**
+ * @fileoverview Rule to disallow a duplicate case label.
+ * @author Dieter Oberkofler
+ * @copyright 2015 Dieter Oberkofler. All rights reserved.
+ */
+
+"use strict";
+
+//------------------------------------------------------------------------------
+// Rule Definition
+//------------------------------------------------------------------------------
+
+module.exports = function(context) {
+
+    /**
+     * Get a hash value for the node
+     * @param {ASTNode} node The node.
+     * @returns {string} A hash value for the node.
+     * @private
+     */
+    function getHash(node) {
+        if (node.type === "Literal") {
+            return node.type + typeof node.value + node.value;
+        } else if (node.type === "Identifier") {
+            return node.type + typeof node.name + node.name;
+        } else if (node.type === "MemberExpression") {
+            return node.type + getHash(node.object) + getHash(node.property);
+        }
+    }
+
+    var switchStatement = [];
+
+    return {
+
+        "SwitchStatement": function(/*node*/) {
+            switchStatement.push({});
+        },
+
+        "SwitchStatement:exit": function(/*node*/) {
+            switchStatement.pop();
+        },
+
+        "SwitchCase": function(node) {
+            var currentSwitch = switchStatement[switchStatement.length - 1],
+                hashValue;
+
+            if (node.test) {
+                hashValue = getHash(node.test);
+                if (typeof hashValue !== "undefined" && currentSwitch.hasOwnProperty(hashValue)) {
+                    context.report(node, "Duplicate case label.");
+                } else {
+                    currentSwitch[hashValue] = true;
+                }
+            }
+        }
+
+    };
+
+};