tools: update ESLint to 2.7.0

PR-URL: https://github.com/nodejs/node/pull/6132
Reviewed-By: Brian White <mscdex@mscdex.net>
Reviewed-By: Jeremiah Senkpiel <fishrock123@rocketmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: thefourtheye <thechargingvolcano@gmail.com>

7 files changed, 346 insertions, 63 deletions

diff --git a/tools/eslint/lib/code-path-analysis/code-path-analyzer.js b/tools/eslint/lib/code-path-analysis/code-path-analyzer.js
index aa2a6ff4ac..afb9980430 100644
--- a/tools/eslint/lib/code-path-analysis/code-path-analyzer.js
+++ b/tools/eslint/lib/code-path-analysis/code-path-analyzer.js
@@ -41,6 +41,7 @@ function isCaseNode(node) {
  */
 function isForkingByTrueOrFalse(node) {
     var parent = node.parent;
+
     switch (parent.type) {
         case "ConditionalExpression":
         case "IfStatement":
@@ -128,8 +129,8 @@ function isIdentifierReference(node) {
  *
  * To separate the current and the head is in order to not make useless segments.
  *
- * In this process, both "onCodePathSegmentStart" and "onCodePathSegmentEnd" events
- * are fired.
+ * In this process, both "onCodePathSegmentStart" and "onCodePathSegmentEnd"
+ * events are fired.
  *
  * @param {CodePathAnalyzer} analyzer - The instance.
  * @param {ASTNode} node - The current AST node.
@@ -206,6 +207,7 @@ function leaveFromCurrentSegment(analyzer, node) {
                 node);
         }
     }
+
     state.currentSegments = [];
 }
 
@@ -234,9 +236,12 @@ function preprocess(analyzer, node) {
 
         case "ConditionalExpression":
         case "IfStatement":
-            // Fork if this node is at `consequent`/`alternate`.
-            // `popForkContext()` exists at `IfStatement:exit` and
-            // `ConditionalExpression:exit`.
+
+            /*
+             * Fork if this node is at `consequent`/`alternate`.
+             * `popForkContext()` exists at `IfStatement:exit` and
+             * `ConditionalExpression:exit`.
+             */
             if (parent.consequent === node) {
                 state.makeIfConsequent();
             } else if (parent.alternate === node) {
@@ -299,9 +304,12 @@ function preprocess(analyzer, node) {
             break;
 
         case "AssignmentPattern":
-            // Fork if this node is at `right`.
-            // `left` is executed always, so it uses the current path.
-            // `popForkContext()` exists at `AssignmentPattern:exit`.
+
+            /*
+             * Fork if this node is at `right`.
+             * `left` is executed always, so it uses the current path.
+             * `popForkContext()` exists at `AssignmentPattern:exit`.
+             */
             if (parent.right === node) {
                 state.pushForkContext();
                 state.forkBypassPath();
@@ -332,6 +340,7 @@ function processCodePathToEnter(analyzer, node) {
         case "FunctionExpression":
         case "ArrowFunctionExpression":
             if (codePath) {
+
                 // Emits onCodePathSegmentStart events if updated.
                 forwardCurrentToHead(analyzer, node);
                 debug.dumpState(node, state, false);
@@ -370,9 +379,12 @@ function processCodePathToEnter(analyzer, node) {
             break;
 
         case "SwitchCase":
-            // Fork if this node is after the 2st node in `cases`.
-            // It's similar to `else` blocks.
-            // The next `test` node is processed in this path.
+
+            /*
+             * Fork if this node is after the 2st node in `cases`.
+             * It's similar to `else` blocks.
+             * The next `test` node is processed in this path.
+             */
             if (parent.discriminant !== node && parent.cases[0] !== node) {
                 state.forkPath();
             }
@@ -425,9 +437,12 @@ function processCodePathToExit(analyzer, node) {
             break;
 
         case "SwitchCase":
-            // This is the same as the process at the 1st `consequent` node in
-            // `preprocess` function.
-            // Must do if this `consequent` is empty.
+
+            /*
+             * This is the same as the process at the 1st `consequent` node in
+             * `preprocess` function.
+             * Must do if this `consequent` is empty.
+             */
             if (node.consequent.length === 0) {
                 state.makeSwitchCaseBody(true, !node.test);
             }
@@ -499,9 +514,12 @@ function processCodePathToExit(analyzer, node) {
             break;
     }
 
-    // Skip updating the current segment to avoid creating useless segments if
-    // the node type is the same as the parent node type.
+    /*
+     * Skip updating the current segment to avoid creating useless segments if
+     * the node type is the same as the parent node type.
+     */
     if (!dontForward && (!node.parent || node.type !== node.parent.type)) {
+
         // Emits onCodePathSegmentStart events if updated.
         forwardCurrentToHead(analyzer, node);
     }
diff --git a/tools/eslint/lib/code-path-analysis/code-path-segment.js b/tools/eslint/lib/code-path-analysis/code-path-segment.js
index 94deafbfbb..ea292efc36 100644
--- a/tools/eslint/lib/code-path-analysis/code-path-segment.js
+++ b/tools/eslint/lib/code-path-analysis/code-path-segment.js
@@ -79,6 +79,7 @@ function isReachable(segment) {
  * @param {boolean} reachable - A flag which shows this is reachable.
  */
 function CodePathSegment(id, allPrevSegments, reachable) {
+
     /**
      * The identifier of this code path.
      * Rules use it to store additional information of each rule.
@@ -120,7 +121,8 @@ function CodePathSegment(id, allPrevSegments, reachable) {
 
     // Internal data.
     Object.defineProperty(this, "internal", {value: {
-        used: false
+        used: false,
+        loopedPrevSegments: []
     }});
 
     /* istanbul ignore if */
@@ -130,6 +132,20 @@ function CodePathSegment(id, allPrevSegments, reachable) {
     }
 }
 
+CodePathSegment.prototype = {
+    constructor: CodePathSegment,
+
+    /**
+     * Checks a given previous segment is coming from the end of a loop.
+     *
+     * @param {CodePathSegment} segment - A previous segment to check.
+     * @returns {boolean} `true` if the segment is coming from the end of a loop.
+     */
+    isLoopedPrevSegment: function(segment) {
+        return this.internal.loopedPrevSegments.indexOf(segment) !== -1;
+    }
+};
+
 /**
  * Creates the root segment.
  *
@@ -191,6 +207,7 @@ CodePathSegment.markUsed = function(segment) {
     segment.internal.used = true;
 
     var i;
+
     if (segment.reachable) {
         for (i = 0; i < segment.allPrevSegments.length; ++i) {
             var prevSegment = segment.allPrevSegments[i];
@@ -205,4 +222,15 @@ CodePathSegment.markUsed = function(segment) {
     }
 };
 
+/**
+ * Marks a previous segment as looped.
+ *
+ * @param {CodePathSegment} segment - A segment.
+ * @param {CodePathSegment} prevSegment - A previous segment to mark.
+ * @returns {void}
+ */
+CodePathSegment.markPrevSegmentAsLooped = function(segment, prevSegment) {
+    segment.internal.loopedPrevSegments.push(prevSegment);
+};
+
 module.exports = CodePathSegment;
diff --git a/tools/eslint/lib/code-path-analysis/code-path-state.js b/tools/eslint/lib/code-path-analysis/code-path-state.js
index 121df319fa..b620ed718b 100644
--- a/tools/eslint/lib/code-path-analysis/code-path-state.js
+++ b/tools/eslint/lib/code-path-analysis/code-path-state.js
@@ -55,6 +55,7 @@ function getContinueContext(state, label) {
     }
 
     var context = state.loopContext;
+
     while (context) {
         if (context.label === label) {
             return context;
@@ -75,6 +76,7 @@ function getContinueContext(state, label) {
  */
 function getBreakContext(state, label) {
     var context = state.breakContext;
+
     while (context) {
         if (label ? context.label === label : context.breakable) {
             return context;
@@ -94,6 +96,7 @@ function getBreakContext(state, label) {
  */
 function getReturnContext(state) {
     var context = state.tryContext;
+
     while (context) {
         if (context.hasFinalizer && context.position !== "finally") {
             return context;
@@ -112,6 +115,7 @@ function getReturnContext(state) {
  */
 function getThrowContext(state) {
     var context = state.tryContext;
+
     while (context) {
         if (context.position === "try" ||
             (context.hasFinalizer && context.position === "catch")
@@ -168,6 +172,7 @@ function removeConnection(prevSegments, nextSegments) {
  */
 function makeLooped(state, fromSegments, toSegments) {
     var end = Math.min(fromSegments.length, toSegments.length);
+
     for (var i = 0; i < end; ++i) {
         var fromSegment = fromSegments[i];
         var toSegment = toSegments[i];
@@ -181,6 +186,10 @@ function makeLooped(state, fromSegments, toSegments) {
         fromSegment.allNextSegments.push(toSegment);
         toSegment.allPrevSegments.push(fromSegment);
 
+        if (toSegment.allPrevSegments.length >= 2) {
+            CodePathSegment.markPrevSegmentAsLooped(toSegment, fromSegment);
+        }
+
         state.notifyLooped(fromSegment, toSegment);
     }
 }
@@ -237,6 +246,7 @@ function CodePathState(idGenerator, onLooped) {
     var final = this.finalSegments = [];
     var returned = this.returnedForkContext = [];
     var thrown = this.thrownForkContext = [];
+
     returned.add = addToReturnedOrThrown.bind(null, returned, thrown, final);
     thrown.add = addToReturnedOrThrown.bind(null, thrown, returned, final);
 }
@@ -259,6 +269,7 @@ CodePathState.prototype = {
      */
     get parentForkContext() {
         var current = this.forkContext;
+
         return current && current.upper;
     },
 
@@ -362,6 +373,7 @@ CodePathState.prototype = {
      */
     popChoiceContext: function() {
         var context = this.choiceContext;
+
         this.choiceContext = context.upper;
 
         var forkContext = this.forkContext;
@@ -370,43 +382,61 @@ CodePathState.prototype = {
         switch (context.kind) {
             case "&&":
             case "||":
-                // If any result were not transferred from child contexts,
-                // this sets the head segments to both cases.
-                // The head segments are the path of the right-hand operand.
+
+                /*
+                 * If any result were not transferred from child contexts,
+                 * this sets the head segments to both cases.
+                 * The head segments are the path of the right-hand operand.
+                 */
                 if (!context.processed) {
                     context.trueForkContext.add(headSegments);
                     context.falseForkContext.add(headSegments);
                 }
 
-                // Transfers results to upper context if this context is in
-                // test chunk.
+                /*
+                 * Transfers results to upper context if this context is in
+                 * test chunk.
+                 */
                 if (context.isForkingAsResult) {
                     var parentContext = this.choiceContext;
+
                     parentContext.trueForkContext.addAll(context.trueForkContext);
                     parentContext.falseForkContext.addAll(context.falseForkContext);
                     parentContext.processed = true;
 
                     return context;
                 }
+
                 break;
 
             case "test":
                 if (!context.processed) {
-                    // The head segments are the path of the `if` block here.
-                    // Updates the `true` path with the end of the `if` block.
+
+                    /*
+                     * The head segments are the path of the `if` block here.
+                     * Updates the `true` path with the end of the `if` block.
+                     */
                     context.trueForkContext.clear();
                     context.trueForkContext.add(headSegments);
                 } else {
-                    // The head segments are the path of the `else` block here.
-                    // Updates the `false` path with the end of the `else` block.
+
+                    /*
+                     * The head segments are the path of the `else` block here.
+                     * Updates the `false` path with the end of the `else`
+                     * block.
+                     */
                     context.falseForkContext.clear();
                     context.falseForkContext.add(headSegments);
                 }
+
                 break;
 
             case "loop":
-                // Loops are addressed in popLoopContext().
-                // This is called from popLoopContext().
+
+                /*
+                 * Loops are addressed in popLoopContext().
+                 * This is called from popLoopContext().
+                 */
                 return context;
 
             /* istanbul ignore next */
@@ -416,6 +446,7 @@ CodePathState.prototype = {
 
         // Merges all paths.
         var prevForkContext = context.trueForkContext;
+
         prevForkContext.addAll(context.falseForkContext);
         forkContext.replaceHead(prevForkContext.makeNext(0, -1));
 
@@ -433,8 +464,11 @@ CodePathState.prototype = {
         var forkContext = this.forkContext;
 
         if (context.processed) {
-            // This got segments already from the child choice context.
-            // Creates the next path from own true/false fork context.
+
+            /*
+             * This got segments already from the child choice context.
+             * Creates the next path from own true/false fork context.
+             */
             var prevForkContext =
                 context.kind === "&&" ? context.trueForkContext :
                 /* kind === "||" */ context.falseForkContext;
@@ -444,13 +478,18 @@ CodePathState.prototype = {
 
             context.processed = false;
         } else {
-            // This did not get segments from the child choice context.
-            // So addresses the head segments.
-            // The head segments are the path of the left-hand operand.
+
+            /*
+             * This did not get segments from the child choice context.
+             * So addresses the head segments.
+             * The head segments are the path of the left-hand operand.
+             */
             if (context.kind === "&&") {
+
                 // The path does short-circuit if false.
                 context.falseForkContext.add(forkContext.head);
             } else {
+
                 // The path does short-circuit if true.
                 context.trueForkContext.add(forkContext.head);
             }
@@ -468,13 +507,16 @@ CodePathState.prototype = {
         var context = this.choiceContext;
         var forkContext = this.forkContext;
 
-        // If any result were not transferred from child contexts,
-        // this sets the head segments to both cases.
-        // The head segments are the path of the test expression.
+        /*
+         * If any result were not transferred from child contexts,
+         * this sets the head segments to both cases.
+         * The head segments are the path of the test expression.
+         */
         if (!context.processed) {
             context.trueForkContext.add(forkContext.head);
             context.falseForkContext.add(forkContext.head);
         }
+
         context.processed = false;
 
         // Creates new path from the `true` case.
@@ -492,8 +534,10 @@ CodePathState.prototype = {
         var context = this.choiceContext;
         var forkContext = this.forkContext;
 
-        // The head segments are the path of the `if` block.
-        // Updates the `true` path with the end of the `if` block.
+        /*
+         * The head segments are the path of the `if` block.
+         * Updates the `true` path with the end of the `if` block.
+         */
         context.trueForkContext.clear();
         context.trueForkContext.add(forkContext.head);
         context.processed = true;
@@ -526,6 +570,7 @@ CodePathState.prototype = {
             lastIsDefault: false,
             countForks: 0
         };
+
         this.pushBreakContext(true, label);
     },
 
@@ -541,41 +586,57 @@ CodePathState.prototype = {
      */
     popSwitchContext: function() {
         var context = this.switchContext;
+
         this.switchContext = context.upper;
 
         var forkContext = this.forkContext;
         var brokenForkContext = this.popBreakContext().brokenForkContext;
 
         if (context.countForks === 0) {
-            // When there is only one `default` chunk and there is one or more
-            // `break` statements, even if forks are nothing, it needs to merge
-            // those.
+
+            /*
+             * When there is only one `default` chunk and there is one or more
+             * `break` statements, even if forks are nothing, it needs to merge
+             * those.
+             */
             if (!brokenForkContext.empty) {
                 brokenForkContext.add(forkContext.makeNext(-1, -1));
                 forkContext.replaceHead(brokenForkContext.makeNext(0, -1));
             }
+
             return;
         }
 
         var lastSegments = forkContext.head;
+
         this.forkBypassPath();
         var lastCaseSegments = forkContext.head;
 
-        // `brokenForkContext` is used to make the next segment.
-        // It must add the last segment into `brokenForkContext`.
+        /*
+         * `brokenForkContext` is used to make the next segment.
+         * It must add the last segment into `brokenForkContext`.
+         */
         brokenForkContext.add(lastSegments);
 
-        // A path which is failed in all case test should be connected to path
-        // of `default` chunk.
+        /*
+         * A path which is failed in all case test should be connected to path
+         * of `default` chunk.
+         */
         if (!context.lastIsDefault) {
             if (context.defaultBodySegments) {
-                // Remove a link from `default` label to its chunk.
-                // It's false route.
+
+                /*
+                 * Remove a link from `default` label to its chunk.
+                 * It's false route.
+                 */
                 removeConnection(context.defaultSegments, context.defaultBodySegments);
                 makeLooped(this, lastCaseSegments, context.defaultBodySegments);
             } else {
-                // It handles the last case body as broken if `default` chunk
-                // does not exist.
+
+                /*
+                 * It handles the last case body as broken if `default` chunk
+                 * does not exist.
+                 */
                 brokenForkContext.add(lastCaseSegments);
             }
         }
@@ -584,8 +645,11 @@ CodePathState.prototype = {
         for (var i = 0; i < context.countForks; ++i) {
             this.forkContext = this.forkContext.upper;
         }
-        // Creates a path from all brokenForkContext paths.
-        // This is a path after switch statement.
+
+        /*
+         * Creates a path from all brokenForkContext paths.
+         * This is a path after switch statement.
+         */
         this.forkContext.replaceHead(brokenForkContext.makeNext(0, -1));
     },
 
@@ -598,20 +662,26 @@ CodePathState.prototype = {
      */
     makeSwitchCaseBody: function(isEmpty, isDefault) {
         var context = this.switchContext;
+
         if (!context.hasCase) {
             return;
         }
 
-        // Merge forks.
-        // The parent fork context has two segments.
-        // Those are from the current case and the body of the previous case.
+        /*
+         * Merge forks.
+         * The parent fork context has two segments.
+         * Those are from the current case and the body of the previous case.
+         */
         var parentForkContext = this.forkContext;
         var forkContext = this.pushForkContext();
+
         forkContext.add(parentForkContext.makeNext(0, -1));
 
-        // Save `default` chunk info.
-        // If the `default` label is not at the last, we must make a path from
-        // the last `case` to the `default` chunk.
+        /*
+         * Save `default` chunk info.
+         * If the `default` label is not at the last, we must make a path from
+         * the last `case` to the `default` chunk.
+         */
         if (isDefault) {
             context.defaultSegments = parentForkContext.head;
             if (isEmpty) {
@@ -625,6 +695,7 @@ CodePathState.prototype = {
                 context.defaultBodySegments = forkContext.head;
             }
         }
+
         context.lastIsDefault = isDefault;
         context.countForks += 1;
     },
@@ -645,9 +716,11 @@ CodePathState.prototype = {
             upper: this.tryContext,
             position: "try",
             hasFinalizer: hasFinalizer,
+
             returnedForkContext: hasFinalizer
                 ? ForkContext.newEmpty(this.forkContext)
                 : null,
+
             thrownForkContext: ForkContext.newEmpty(this.forkContext),
             lastOfTryIsReachable: false,
             lastOfCatchIsReachable: false
@@ -661,24 +734,31 @@ CodePathState.prototype = {
      */
     popTryContext: function() {
         var context = this.tryContext;
+
         this.tryContext = context.upper;
 
         if (context.position === "catch") {
+
             // Merges two paths from the `try` block and `catch` block merely.
             this.popForkContext();
             return;
         }
-        // The following process is executed only when there is the `finally`
-        // block.
+
+        /*
+         * The following process is executed only when there is the `finally`
+         * block.
+         */
 
         var returned = context.returnedForkContext;
         var thrown = context.thrownForkContext;
+
         if (returned.empty && thrown.empty) {
             return;
         }
 
         // Separate head to normal paths and leaving paths.
         var headSegments = this.forkContext.head;
+
         this.forkContext = this.forkContext.upper;
         var normalSegments = headSegments.slice(0, headSegments.length / 2 | 0);
         var leavingSegments = headSegments.slice(headSegments.length / 2 | 0);
@@ -744,6 +824,7 @@ CodePathState.prototype = {
 
         // Update state.
         if (context.position === "catch") {
+
             // Merges two paths from the `try` block and `catch` block.
             this.popForkContext();
             forkContext = this.forkContext;
@@ -755,14 +836,18 @@ CodePathState.prototype = {
         context.position = "finally";
 
         if (returned.empty && thrown.empty) {
+
             // This path does not leave.
             return;
         }
 
-        // Create a parallel segment from merging returned and thrown.
-        // This segment will leave at the end of this finally block.
+        /*
+         * Create a parallel segment from merging returned and thrown.
+         * This segment will leave at the end of this finally block.
+         */
         var segments = forkContext.makeNext(-1, -1);
         var j;
+
         for (var i = 0; i < forkContext.count; ++i) {
             var prevSegsOfLeavingSegment = [headOfLeavingSegments[i]];
 
@@ -790,11 +875,13 @@ CodePathState.prototype = {
      */
     makeFirstThrowablePathInTryBlock: function() {
         var forkContext = this.forkContext;
+
         if (!forkContext.reachable) {
             return;
         }
 
         var context = getThrowContext(this);
+
         if (context === this ||
             context.position !== "try" ||
             !context.thrownForkContext.empty
@@ -893,6 +980,7 @@ CodePathState.prototype = {
      */
     popLoopContext: function() {
         var context = this.loopContext;
+
         this.loopContext = context.upper;
 
         var forkContext = this.forkContext;
@@ -923,6 +1011,7 @@ CodePathState.prototype = {
 
                 // `true` paths go to looping.
                 var segmentsList = choiceContext.trueForkContext.segmentsList;
+
                 for (var i = 0; i < segmentsList.length; ++i) {
                     makeLooped(
                         this,
@@ -1069,6 +1158,7 @@ CodePathState.prototype = {
 
         // Update state.
         var updateSegments = forkContext.makeDisconnected(-1, -1);
+
         context.continueDestSegments = context.updateSegments = updateSegments;
         forkContext.replaceHead(updateSegments);
     },
@@ -1104,10 +1194,15 @@ CodePathState.prototype = {
         }
 
         var bodySegments = context.endOfTestSegments;
+
         if (!bodySegments) {
-            // If there is not the `test` part, the `body` path comes from the
-            // `init` part and the `update` part.
+
+            /*
+             * If there is not the `test` part, the `body` path comes from the
+             * `init` part and the `update` part.
+             */
             var prevForkContext = ForkContext.newEmpty(forkContext);
+
             prevForkContext.add(context.endOfInitSegments);
             if (context.endOfUpdateSegments) {
                 prevForkContext.add(context.endOfUpdateSegments);
@@ -1146,6 +1241,7 @@ CodePathState.prototype = {
         var context = this.loopContext;
         var forkContext = this.forkContext;
         var temp = ForkContext.newEmpty(forkContext);
+
         temp.add(context.prevSegments);
         var rightSegments = temp.makeNext(-1, -1);
 
@@ -1164,6 +1260,7 @@ CodePathState.prototype = {
         var context = this.loopContext;
         var forkContext = this.forkContext;
         var temp = ForkContext.newEmpty(forkContext);
+
         temp.add(context.endOfLeftSegments);
         var bodySegments = temp.makeNext(-1, -1);
 
@@ -1205,11 +1302,13 @@ CodePathState.prototype = {
     popBreakContext: function() {
         var context = this.breakContext;
         var forkContext = this.forkContext;
+
         this.breakContext = context.upper;
 
         // Process this context here for other than switches and loops.
         if (!context.breakable) {
             var brokenForkContext = context.brokenForkContext;
+
             if (!brokenForkContext.empty) {
                 brokenForkContext.add(forkContext.head);
                 forkContext.replaceHead(brokenForkContext.makeNext(0, -1));
@@ -1230,15 +1329,18 @@ CodePathState.prototype = {
      */
     makeBreak: function(label) {
         var forkContext = this.forkContext;
+
         if (!forkContext.reachable) {
             return;
         }
 
         var context = getBreakContext(this, label);
+
         /* istanbul ignore else: foolproof (syntax error) */
         if (context) {
             context.brokenForkContext.add(forkContext.head);
         }
+
         forkContext.replaceHead(forkContext.makeUnreachable(-1, -1));
     },
 
@@ -1253,11 +1355,13 @@ CodePathState.prototype = {
      */
     makeContinue: function(label) {
         var forkContext = this.forkContext;
+
         if (!forkContext.reachable) {
             return;
         }
 
         var context = getContinueContext(this, label);
+
         /* istanbul ignore else: foolproof (syntax error) */
         if (context) {
             if (context.continueDestSegments) {
@@ -1286,6 +1390,7 @@ CodePathState.prototype = {
      */
     makeReturn: function() {
         var forkContext = this.forkContext;
+
         if (forkContext.reachable) {
             getReturnContext(this).returnedForkContext.add(forkContext.head);
             forkContext.replaceHead(forkContext.makeUnreachable(-1, -1));
@@ -1302,6 +1407,7 @@ CodePathState.prototype = {
      */
     makeThrow: function() {
         var forkContext = this.forkContext;
+
         if (forkContext.reachable) {
             getThrowContext(this).thrownForkContext.add(forkContext.head);
             forkContext.replaceHead(forkContext.makeUnreachable(-1, -1));
@@ -1314,6 +1420,7 @@ CodePathState.prototype = {
      */
     makeFinal: function() {
         var segments = this.currentSegments;
+
         if (segments.length > 0 && segments[0].reachable) {
             this.returnedForkContext.add(segments);
         }
diff --git a/tools/eslint/lib/code-path-analysis/code-path.js b/tools/eslint/lib/code-path-analysis/code-path.js
index 200ff434b8..2b45ed944f 100644
--- a/tools/eslint/lib/code-path-analysis/code-path.js
+++ b/tools/eslint/lib/code-path-analysis/code-path.js
@@ -27,6 +27,7 @@ var IdGenerator = require("./id-generator");
  * @param {function} onLooped - A callback function to notify looping.
  */
 function CodePath(id, upper, onLooped) {
+
     /**
      * The identifier of this code path.
      * Rules use it to store additional information of each rule.
@@ -102,6 +103,123 @@ CodePath.prototype = {
      */
     get currentSegments() {
         return this.internal.currentSegments;
+    },
+
+    /**
+     * Traverses all segments in this code path.
+     *
+     *     codePath.traverseSegments(function(segment, controller) {
+     *         // do something.
+     *     });
+     *
+     * This method enumerates segments in order from the head.
+     *
+     * The `controller` object has two methods.
+     *
+     * - `controller.skip()` - Skip the following segments in this branch.
+     * - `controller.break()` - Skip all following segments.
+     *
+     * @param {object} [options] - Omittable.
+     * @param {CodePathSegment} [options.first] - The first segment to traverse.
+     * @param {CodePathSegment} [options.last] - The last segment to traverse.
+     * @param {function} callback - A callback function.
+     * @returns {void}
+     */
+    traverseSegments: function(options, callback) {
+        if (typeof options === "function") {
+            callback = options;
+            options = null;
+        }
+
+        options = options || {};
+        var startSegment = options.first || this.internal.initialSegment;
+        var lastSegment = options.last;
+
+        var item = null;
+        var index = 0;
+        var end = 0;
+        var segment = null;
+        var visited = Object.create(null);
+        var stack = [[startSegment, 0]];
+        var skippedSegment = null;
+        var broken = false;
+        var controller = {
+            skip: function() {
+                if (stack.length <= 1) {
+                    broken = true;
+                } else {
+                    skippedSegment = stack[stack.length - 2][0];
+                }
+            },
+            break: function() {
+                broken = true;
+            }
+        };
+
+        /**
+         * Checks a given previous segment has been visited.
+         * @param {CodePathSegment} prevSegment - A previous segment to check.
+         * @returns {boolean} `true` if the segment has been visited.
+         */
+        function isVisited(prevSegment) {
+            return (
+                visited[prevSegment.id] ||
+                segment.isLoopedPrevSegment(prevSegment)
+            );
+        }
+
+        while (stack.length > 0) {
+            item = stack[stack.length - 1];
+            segment = item[0];
+            index = item[1];
+
+            if (index === 0) {
+
+                // Skip if this segment has been visited already.
+                if (visited[segment.id]) {
+                    stack.pop();
+                    continue;
+                }
+
+                // Skip if all previous segments have not been visited.
+                if (segment !== startSegment &&
+                    segment.prevSegments.length > 0 &&
+                    !segment.prevSegments.every(isVisited)
+                ) {
+                    stack.pop();
+                    continue;
+                }
+
+                // Reset the flag of skipping if all branches have been skipped.
+                if (skippedSegment && segment.prevSegments.indexOf(skippedSegment) !== -1) {
+                    skippedSegment = null;
+                }
+                visited[segment.id] = true;
+
+                // Call the callback when the first time.
+                if (!skippedSegment) {
+                    callback.call(this, segment, controller); // eslint-disable-line callback-return
+                    if (segment === lastSegment) {
+                        controller.skip();
+                    }
+                    if (broken) {
+                        break;
+                    }
+                }
+            }
+
+            // Update the stack.
+            end = segment.nextSegments.length - 1;
+            if (index < end) {
+                item[1] += 1;
+                stack.push([segment.nextSegments[index], 0]);
+            } else if (index === end) {
+                item[0] = segment.nextSegments[index];
+                item[1] = 0;
+            } else {
+                stack.pop();
+            }
+        }
     }
 };
 
diff --git a/tools/eslint/lib/code-path-analysis/debug-helpers.js b/tools/eslint/lib/code-path-analysis/debug-helpers.js
index d8c26ad1b8..6ecfabe955 100644
--- a/tools/eslint/lib/code-path-analysis/debug-helpers.js
+++ b/tools/eslint/lib/code-path-analysis/debug-helpers.js
@@ -32,6 +32,7 @@ function getId(segment) { // eslint-disable-line require-jsdoc
 //------------------------------------------------------------------------------
 
 module.exports = {
+
     /**
      * A flag that debug dumping is enabled or not.
      * @type {boolean}
@@ -57,6 +58,7 @@ module.exports = {
     dumpState: !debug.enabled ? debug : /* istanbul ignore next */ function(node, state, leaving) {
         for (var i = 0; i < state.currentSegments.length; ++i) {
             var segInternal = state.currentSegments[i].internal;
+
             if (leaving) {
                 segInternal.exitNodes.push(node);
             } else {
@@ -153,12 +155,14 @@ module.exports = {
             var item = stack.pop();
             var segment = item[0];
             var index = item[1];
+
             if (done[segment.id] && index === 0) {
                 continue;
             }
             done[segment.id] = segment;
 
             var nextSegment = segment.allNextSegments[index];
+
             if (!nextSegment) {
                 continue;
             }
diff --git a/tools/eslint/lib/code-path-analysis/fork-context.js b/tools/eslint/lib/code-path-analysis/fork-context.js
index 8716ddd6ff..af82e68e0c 100644
--- a/tools/eslint/lib/code-path-analysis/fork-context.js
+++ b/tools/eslint/lib/code-path-analysis/fork-context.js
@@ -47,6 +47,7 @@ function isReachable(segment) {
  */
 function makeSegments(context, begin, end, create) {
     var list = context.segmentsList;
+
     if (begin < 0) {
         begin = list.length + begin;
     }
@@ -55,6 +56,7 @@ function makeSegments(context, begin, end, create) {
     }
 
     var segments = [];
+
     for (var i = 0; i < context.count; ++i) {
         var allPrevSegments = [];
 
@@ -81,6 +83,7 @@ function makeSegments(context, begin, end, create) {
 function mergeExtraSegments(context, segments) {
     while (segments.length > context.count) {
         var merged = [];
+
         for (var i = 0, length = segments.length / 2 | 0; i < length; ++i) {
             merged.push(CodePathSegment.newNext(
                 context.idGenerator.next(),
@@ -120,6 +123,7 @@ ForkContext.prototype = {
      */
     get head() {
         var list = this.segmentsList;
+
         return list.length === 0 ? [] : list[list.length - 1];
     },
 
@@ -137,6 +141,7 @@ ForkContext.prototype = {
      */
     get reachable() {
         var segments = this.head;
+
         return segments.length > 0 && segments.some(isReachable);
     },
 
@@ -212,6 +217,7 @@ ForkContext.prototype = {
         assert(context.count === this.count);
 
         var source = context.segmentsList;
+
         for (var i = 0; i < source.length; ++i) {
             this.segmentsList.push(source[i]);
         }
diff --git a/tools/eslint/lib/code-path-analysis/id-generator.js b/tools/eslint/lib/code-path-analysis/id-generator.js
index c37e7d7e5b..530ea95844 100644
--- a/tools/eslint/lib/code-path-analysis/id-generator.js
+++ b/tools/eslint/lib/code-path-analysis/id-generator.js
@@ -33,10 +33,12 @@ function IdGenerator(prefix) {
  */
 IdGenerator.prototype.next = function() {
     this.n = 1 + this.n | 0;
+
     /* istanbul ignore if */
     if (this.n < 0) {
         this.n = 1;
     }
+
     return this.prefix + this.n;
 };