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diff --git a/tools/node_modules/eslint/lib/rules/no-else-return.js b/tools/node_modules/eslint/lib/rules/no-else-return.js
new file mode 100644
index 0000000000..deeff41ab8
--- /dev/null
+++ b/tools/node_modules/eslint/lib/rules/no-else-return.js
@@ -0,0 +1,276 @@
+/**
+ * @fileoverview Rule to flag `else` after a `return` in `if`
+ * @author Ian Christian Myers
+ */
+
+"use strict";
+
+//------------------------------------------------------------------------------
+// Requirements
+//------------------------------------------------------------------------------
+
+const astUtils = require("../ast-utils");
+const FixTracker = require("../util/fix-tracker");
+
+//------------------------------------------------------------------------------
+// Rule Definition
+//------------------------------------------------------------------------------
+
+module.exports = {
+    meta: {
+        docs: {
+            description: "disallow `else` blocks after `return` statements in `if` statements",
+            category: "Best Practices",
+            recommended: false
+        },
+
+        schema: [{
+            type: "object",
+            properties: {
+                allowElseIf: {
+                    type: "boolean"
+                }
+            },
+            additionalProperties: false
+        }],
+        fixable: "code"
+    },
+
+    create(context) {
+
+        //--------------------------------------------------------------------------
+        // Helpers
+        //--------------------------------------------------------------------------
+
+        /**
+         * Display the context report if rule is violated
+         *
+         * @param {Node} node The 'else' node
+         * @returns {void}
+         */
+        function displayReport(node) {
+            context.report({
+                node,
+                message: "Unnecessary 'else' after 'return'.",
+                fix: fixer => {
+                    const sourceCode = context.getSourceCode();
+                    const startToken = sourceCode.getFirstToken(node);
+                    const elseToken = sourceCode.getTokenBefore(startToken);
+                    const source = sourceCode.getText(node);
+                    const lastIfToken = sourceCode.getTokenBefore(elseToken);
+                    let fixedSource, firstTokenOfElseBlock;
+
+                    if (startToken.type === "Punctuator" && startToken.value === "{") {
+                        firstTokenOfElseBlock = sourceCode.getTokenAfter(startToken);
+                    } else {
+                        firstTokenOfElseBlock = startToken;
+                    }
+
+                    /*
+                     * If the if block does not have curly braces and does not end in a semicolon
+                     * and the else block starts with (, [, /, +, ` or -, then it is not
+                     * safe to remove the else keyword, because ASI will not add a semicolon
+                     * after the if block
+                     */
+                    const ifBlockMaybeUnsafe = node.parent.consequent.type !== "BlockStatement" && lastIfToken.value !== ";";
+                    const elseBlockUnsafe = /^[([/+`-]/.test(firstTokenOfElseBlock.value);
+
+                    if (ifBlockMaybeUnsafe && elseBlockUnsafe) {
+                        return null;
+                    }
+
+                    const endToken = sourceCode.getLastToken(node);
+                    const lastTokenOfElseBlock = sourceCode.getTokenBefore(endToken);
+
+                    if (lastTokenOfElseBlock.value !== ";") {
+                        const nextToken = sourceCode.getTokenAfter(endToken);
+
+                        const nextTokenUnsafe = nextToken && /^[([/+`-]/.test(nextToken.value);
+                        const nextTokenOnSameLine = nextToken && nextToken.loc.start.line === lastTokenOfElseBlock.loc.start.line;
+
+                        /*
+                         * If the else block contents does not end in a semicolon,
+                         * and the else block starts with (, [, /, +, ` or -, then it is not
+                         * safe to remove the else block, because ASI will not add a semicolon
+                         * after the remaining else block contents
+                         */
+                        if (nextTokenUnsafe || (nextTokenOnSameLine && nextToken.value !== "}")) {
+                            return null;
+                        }
+                    }
+
+                    if (startToken.type === "Punctuator" && startToken.value === "{") {
+                        fixedSource = source.slice(1, -1);
+                    } else {
+                        fixedSource = source;
+                    }
+
+                    /*
+                     * Extend the replacement range to include the entire
+                     * function to avoid conflicting with no-useless-return.
+                     * https://github.com/eslint/eslint/issues/8026
+                     */
+                    return new FixTracker(fixer, sourceCode)
+                        .retainEnclosingFunction(node)
+                        .replaceTextRange([elseToken.range[0], node.range[1]], fixedSource);
+                }
+            });
+        }
+
+        /**
+         * Check to see if the node is a ReturnStatement
+         *
+         * @param {Node} node The node being evaluated
+         * @returns {boolean} True if node is a return
+         */
+        function checkForReturn(node) {
+            return node.type === "ReturnStatement";
+        }
+
+        /**
+         * Naive return checking, does not iterate through the whole
+         * BlockStatement because we make the assumption that the ReturnStatement
+         * will be the last node in the body of the BlockStatement.
+         *
+         * @param {Node} node The consequent/alternate node
+         * @returns {boolean} True if it has a return
+         */
+        function naiveHasReturn(node) {
+            if (node.type === "BlockStatement") {
+                const body = node.body,
+                    lastChildNode = body[body.length - 1];
+
+                return lastChildNode && checkForReturn(lastChildNode);
+            }
+            return checkForReturn(node);
+        }
+
+        /**
+         * Check to see if the node is valid for evaluation,
+         * meaning it has an else.
+         *
+         * @param {Node} node The node being evaluated
+         * @returns {boolean} True if the node is valid
+         */
+        function hasElse(node) {
+            return node.alternate && node.consequent;
+        }
+
+        /**
+         * If the consequent is an IfStatement, check to see if it has an else
+         * and both its consequent and alternate path return, meaning this is
+         * a nested case of rule violation.  If-Else not considered currently.
+         *
+         * @param {Node} node The consequent node
+         * @returns {boolean} True if this is a nested rule violation
+         */
+        function checkForIf(node) {
+            return node.type === "IfStatement" && hasElse(node) &&
+                naiveHasReturn(node.alternate) && naiveHasReturn(node.consequent);
+        }
+
+        /**
+         * Check the consequent/body node to make sure it is not
+         * a ReturnStatement or an IfStatement that returns on both
+         * code paths.
+         *
+         * @param {Node} node The consequent or body node
+         * @param {Node} alternate The alternate node
+         * @returns {boolean} `true` if it is a Return/If node that always returns.
+         */
+        function checkForReturnOrIf(node) {
+            return checkForReturn(node) || checkForIf(node);
+        }
+
+
+        /**
+         * Check whether a node returns in every codepath.
+         * @param {Node} node The node to be checked
+         * @returns {boolean} `true` if it returns on every codepath.
+         */
+        function alwaysReturns(node) {
+            if (node.type === "BlockStatement") {
+
+                // If we have a BlockStatement, check each consequent body node.
+                return node.body.some(checkForReturnOrIf);
+            }
+
+            /*
+             * If not a block statement, make sure the consequent isn't a
+             * ReturnStatement or an IfStatement with returns on both paths.
+             */
+            return checkForReturnOrIf(node);
+        }
+
+
+        /**
+         * Check the if statement, but don't catch else-if blocks.
+         * @returns {void}
+         * @param {Node} node The node for the if statement to check
+         * @private
+         */
+        function checkIfWithoutElse(node) {
+            const parent = node.parent;
+            let consequents,
+                alternate;
+
+            /*
+             * Fixing this would require splitting one statement into two, so no error should
+             * be reported if this node is in a position where only one statement is allowed.
+             */
+            if (!astUtils.STATEMENT_LIST_PARENTS.has(parent.type)) {
+                return;
+            }
+
+            for (consequents = []; node.type === "IfStatement"; node = node.alternate) {
+                if (!node.alternate) {
+                    return;
+                }
+                consequents.push(node.consequent);
+                alternate = node.alternate;
+            }
+
+            if (consequents.every(alwaysReturns)) {
+                displayReport(alternate);
+            }
+        }
+
+        /**
+         * Check the if statement
+         * @returns {void}
+         * @param {Node} node The node for the if statement to check
+         * @private
+         */
+        function checkIfWithElse(node) {
+            const parent = node.parent;
+
+
+            /*
+             * Fixing this would require splitting one statement into two, so no error should
+             * be reported if this node is in a position where only one statement is allowed.
+             */
+            if (!astUtils.STATEMENT_LIST_PARENTS.has(parent.type)) {
+                return;
+            }
+
+            const alternate = node.alternate;
+
+            if (alternate && alwaysReturns(node.consequent)) {
+                displayReport(alternate);
+            }
+        }
+
+        const allowElseIf = !(context.options[0] && context.options[0].allowElseIf === false);
+
+        //--------------------------------------------------------------------------
+        // Public API
+        //--------------------------------------------------------------------------
+
+        return {
+
+            "IfStatement:exit": allowElseIf ? checkIfWithoutElse : checkIfWithElse
+
+        };
+
+    }
+};