Add "no-confusing-arrow" eslint check

src/librustdoc/html/static/.eslintrc.js

@@ -78,5 +78,6 @@ module.exports = {
         "block-scoped-var": "error",
         "guard-for-in": "error",
         "no-alert": "error",
+        "no-confusing-arrow": "error",
     }
 };

src/librustdoc/html/static/js/main.js

@@ -882,7 +882,7 @@ function loadCss(cssFileName) {
             ["-", "Collapse all sections"],
         ].map(x => "<dt>" +
             x[0].split(" ")
-                .map((y, index) => (index & 1) === 0 ? "<kbd>" + y + "</kbd>" : " " + y + " ")
+                .map((y, index) => ((index & 1) === 0 ? "<kbd>" + y + "</kbd>" : " " + y + " "))
                 .join("") + "</dt><dd>" + x[1] + "</dd>").join("");
         const div_shortcuts = document.createElement("div");
         addClass(div_shortcuts, "shortcuts");