1 files changed, 67 insertions, 0 deletions
diff --git a/tools/eslint/lib/rules/no-use-before-define.js b/tools/eslint/lib/rules/no-use-before-define.js
new file mode 100644
index 0000000000..3f175dc78b
--- /dev/null
+++ b/tools/eslint/lib/rules/no-use-before-define.js
@@ -0,0 +1,67 @@
+/**
+ * @fileoverview Rule to flag use of variables before they are defined
+ * @author Ilya Volodin
+ * @copyright 2013 Ilya Volodin. All rights reserved.
+ */
+
+"use strict";
+
+//------------------------------------------------------------------------------
+// Constants
+//------------------------------------------------------------------------------
+
+var NO_FUNC = "nofunc";
+
+//------------------------------------------------------------------------------
+// Rule Definition
+//------------------------------------------------------------------------------
+
+module.exports = function(context) {
+
+    function findDeclaration(name, scope) {
+        // try searching in the current scope first
+        for (var i = 0, l = scope.variables.length; i < l; i++) {
+            if (scope.variables[i].name === name) {
+                return scope.variables[i];
+            }
+        }
+        // check if there's upper scope and call recursivly till we find the variable
+        if (scope.upper) {
+            return findDeclaration(name, scope.upper);
+        }
+    }
+
+    function findVariables() {
+        var scope = context.getScope();
+        var typeOption = context.options[0];
+
+        function checkLocationAndReport(reference, declaration) {
+            if (typeOption !== NO_FUNC || declaration.defs[0].type !== "FunctionName") {
+                if (declaration.identifiers[0].range[1] > reference.identifier.range[1]) {
+                    context.report(reference.identifier, "{{a}} was used before it was defined", {a: reference.identifier.name});
+                }
+            }
+        }
+
+        scope.references.forEach(function(reference) {
+            // if the reference is resolved check for declaration location
+            // if not, it could be function invocation, try to find manually
+            if (reference.resolved && reference.resolved.identifiers.length > 0) {
+                checkLocationAndReport(reference, reference.resolved);
+            } else {
+                var declaration = findDeclaration(reference.identifier.name, scope);
+                // if there're no identifiers, this is a global environment variable
+                if (declaration && declaration.identifiers.length !== 0) {
+                    checkLocationAndReport(reference, declaration);
+                }
+            }
+        });
+    }
+
+    return {
+        "Program": findVariables,
+        "FunctionExpression": findVariables,
+        "FunctionDeclaration": findVariables,
+        "ArrowFunctionExpression": findVariables
+    };
+};