1 files changed, 80 insertions, 0 deletions
diff --git a/tools/node_modules/eslint/lib/rules/no-unsafe-negation.js b/tools/node_modules/eslint/lib/rules/no-unsafe-negation.js
new file mode 100644
index 0000000000..761dc03386
--- /dev/null
+++ b/tools/node_modules/eslint/lib/rules/no-unsafe-negation.js
@@ -0,0 +1,80 @@
+/**
+ * @fileoverview Rule to disallow negating the left operand of relational operators
+ * @author Toru Nagashima
+ */
+
+"use strict";
+
+//------------------------------------------------------------------------------
+// Requirements
+//------------------------------------------------------------------------------
+
+const astUtils = require("../ast-utils");
+
+//------------------------------------------------------------------------------
+// Helpers
+//------------------------------------------------------------------------------
+
+/**
+ * Checks whether the given operator is a relational operator or not.
+ *
+ * @param {string} op - The operator type to check.
+ * @returns {boolean} `true` if the operator is a relational operator.
+ */
+function isRelationalOperator(op) {
+    return op === "in" || op === "instanceof";
+}
+
+/**
+ * Checks whether the given node is a logical negation expression or not.
+ *
+ * @param {ASTNode} node - The node to check.
+ * @returns {boolean} `true` if the node is a logical negation expression.
+ */
+function isNegation(node) {
+    return node.type === "UnaryExpression" && node.operator === "!";
+}
+
+//------------------------------------------------------------------------------
+// Rule Definition
+//------------------------------------------------------------------------------
+
+module.exports = {
+    meta: {
+        docs: {
+            description: "disallow negating the left operand of relational operators",
+            category: "Possible Errors",
+            recommended: true
+        },
+        schema: [],
+        fixable: "code"
+    },
+
+    create(context) {
+        const sourceCode = context.getSourceCode();
+
+        return {
+            BinaryExpression(node) {
+                if (isRelationalOperator(node.operator) &&
+                    isNegation(node.left) &&
+                    !astUtils.isParenthesised(sourceCode, node.left)
+                ) {
+                    context.report({
+                        node,
+                        loc: node.left.loc,
+                        message: "Unexpected negating the left operand of '{{operator}}' operator.",
+                        data: node,
+
+                        fix(fixer) {
+                            const negationToken = sourceCode.getFirstToken(node.left);
+                            const fixRange = [negationToken.range[1], node.range[1]];
+                            const text = sourceCode.text.slice(fixRange[0], fixRange[1]);
+
+                            return fixer.replaceTextRange(fixRange, `(${text})`);
+                        }
+                    });
+                }
+            }
+        };
+    }
+};