jshint/src/jshint.js

Static analysis tool for JavaScript

/*!
 * JSHint, by JSHint Community.
 *
 * Licensed under the MIT license.
 *
 * JSHint is a derivative work of JSLint:
 *
 *   Copyright (c) 2002 Douglas Crockford  (www.JSLint.com)
 *
 *   Permission is hereby granted, free of charge, to any person obtaining
 *   a copy of this software and associated documentation files (the "Software"),
 *   to deal in the Software without restriction, including without limitation
 *   the rights to use, copy, modify, merge, publish, distribute, sublicense,
 *   and/or sell copies of the Software, and to permit persons to whom
 *   the Software is furnished to do so, subject to the following conditions:
 *
 *   The above copyright notice and this permission notice shall be included
 *   in all copies or substantial portions of the Software.
 *
 *   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 *   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 *   FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 *   AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 *   LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 *   FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 *   DEALINGS IN THE SOFTWARE.
 *
 */

/*jshint quotmark:double */
/*exported console */

var _            = require("lodash");
var events       = require("events");
var vars         = require("./vars.js");
var messages     = require("./messages.js");
var Lexer        = require("./lex.js").Lexer;
var reg          = require("./reg.js");
var state        = require("./state.js").state;
var style        = require("./style.js");
var options      = require("./options.js");
var scopeManager = require("./scope-manager.js");
var prodParams   = require("./prod-params.js");

// We need this module here because environments such as IE and Rhino
// don't necessarilly expose the 'console' API and browserify uses
// it to log things. It's a sad state of affair, really.
var console = require("console-browserify");

// We build the application inside a function so that we produce only a singleton
// variable. That function will be invoked immediately, and its return value is
// the JSHINT function itself.

var JSHINT = (function() {
  "use strict";

  var api, // Extension API

    // These are operators that should not be used with the ! operator.
    bang = {
      "<"  : true,
      "<=" : true,
      "==" : true,
      "===": true,
      "!==": true,
      "!=" : true,
      ">"  : true,
      ">=" : true,
      "+"  : true,
      "-"  : true,
      "*"  : true,
      "/"  : true,
      "%"  : true
    },

    declared, // Globals that were declared using /*global ... */ syntax.

    functions, // All of the functions

    inblock,
    indent,
    lookahead,
    lex,
    member,
    membersOnly,
    predefined,    // Global variables defined by option

    extraModules = [],
    emitter = new events.EventEmitter();

  function checkOption(name, isStable, t) {
    var type, validNames;

    if (isStable) {
      type = "";
      validNames = options.validNames;
    } else {
      type = "unstable ";
      validNames = options.unstableNames;
    }

    name = name.trim();

    if (/^[+-]W\d{3}$/g.test(name)) {
      return true;
    }

    if (validNames.indexOf(name) === -1) {
      if (t.type !== "jslint" && !_.has(options.removed, name)) {
        error("E001", t, type, name);
        return false;
      }
    }

    return true;
  }

  function isString(obj) {
    return Object.prototype.toString.call(obj) === "[object String]";
  }

  function isIdentifier(tkn, value) {
    if (!tkn)
      return false;

    if (!tkn.identifier || tkn.value !== value)
      return false;

    return true;
  }

  /**
   * ES3 defined a set of "FutureReservedWords" in order "to allow for the
   * possibility of future adoption of [proposed] extensions."
   *
   * ES5 reduced the set of FutureReservedWords, in some cases by using them to
   * define new syntactic forms (e.g. `class` and `const`) and in other cases
   * by simply allowing their use as Identifiers (e.g. `int` and `goto`).
   * Separately, ES5 introduced new restrictions on certain tokens, but limited
   * the restriction to strict mode code (e.g. `let` and `yield`).
   *
   * This function determines if a given token describes a reserved word
   * according to the current state of the parser.
   *
   * @param {number} context - the parsing context; see `prod-params.js` for
   *                           more information
   * @param {Token} token
   */
  function isReserved(context, token) {
    if (!token.reserved) {
      return false;
    }
    var meta = token.meta;

    if (meta && meta.isFutureReservedWord) {
      if (state.inES5()) {
        // ES3 FutureReservedWord in an ES5 environment.
        if (!meta.es5) {
          return false;
        }

        if (token.isProperty) {
          return false;
        }
      }
    } else if (meta && meta.es5 && !state.inES5()) {
      return false;
    }

    // Some identifiers are reserved only within a strict mode environment.
    if (meta && meta.strictOnly && state.inES5()) {
      if (!state.option.strict && !state.isStrict()) {
        return false;
      }
    }

    if (token.id === "await" && (!(context & prodParams.async) && !state.option.module)) {
      return false;
    }

    if (token.id === "yield" && (!(context & prodParams.yield))) {
      return state.isStrict();
    }

    return true;
  }

  function supplant(str, data) {
    return str.replace(/\{([^{}]*)\}/g, function(a, b) {
      var r = data[b];
      return typeof r === "string" || typeof r === "number" ? r : a;
    });
  }

  function combine(dest, src) {
    Object.keys(src).forEach(function(name) {
      if (_.has(JSHINT.blacklist, name)) return;
      dest[name] = src[name];
    });
  }

  function processenforceall() {
    if (state.option.enforceall) {
      for (var enforceopt in options.bool.enforcing) {
        if (state.option[enforceopt] === undefined &&
            !options.noenforceall[enforceopt]) {
          state.option[enforceopt] = true;
        }
      }
      for (var relaxopt in options.bool.relaxing) {
        if (state.option[relaxopt] === undefined) {
          state.option[relaxopt] = false;
        }
      }
    }
  }

  /**
   * Apply all linting options according to the status of the `state` object.
   */
  function applyOptions() {
    var badESOpt = null;
    processenforceall();

    /**
     * TODO: Remove in JSHint 3
     */
    badESOpt = state.inferEsVersion();
    if (badESOpt) {
      quit("E059", state.tokens.next, "esversion", badESOpt);
    }

    if (state.inES5()) {
      combine(predefined, vars.ecmaIdentifiers[5]);
    }

    if (state.inES6()) {
      combine(predefined, vars.ecmaIdentifiers[6]);
    }

    if (state.inES8()) {
      combine(predefined, vars.ecmaIdentifiers[8]);
    }

    if (state.inES11()) {
      combine(predefined, vars.ecmaIdentifiers[11]);
    }

    /**
     * Use `in` to check for the presence of any explicitly-specified value for
     * `globalstrict` because both `true` and `false` should trigger an error.
     */
    if (state.option.strict === "global" && "globalstrict" in state.option) {
      quit("E059", state.tokens.next, "strict", "globalstrict");
    }

    if (state.option.module) {
      /**
       * TODO: Extend this restriction to *all* ES6-specific options.
       */
      if (!state.inES6()) {
        warning("W134", state.tokens.next, "module", 6);
      }
    }

    if (state.option.regexpu) {
      /**
       * TODO: Extend this restriction to *all* ES6-specific options.
       */
      if (!state.inES6()) {
        warning("W134", state.tokens.next, "regexpu", 6);
      }
    }

    if (state.option.couch) {
      combine(predefined, vars.couch);
    }

    if (state.option.qunit) {
      combine(predefined, vars.qunit);
    }

    if (state.option.rhino) {
      combine(predefined, vars.rhino);
    }

    if (state.option.shelljs) {
      combine(predefined, vars.shelljs);
      combine(predefined, vars.node);
    }
    if (state.option.typed) {
      combine(predefined, vars.typed);
    }

    if (state.option.phantom) {
      combine(predefined, vars.phantom);
    }

    if (state.option.prototypejs) {
      combine(predefined, vars.prototypejs);
    }

    if (state.option.node) {
      combine(predefined, vars.node);
      combine(predefined, vars.typed);
    }

    if (state.option.devel) {
      combine(predefined, vars.devel);
    }

    if (state.option.dojo) {
      combine(predefined, vars.dojo);
    }

    if (state.option.browser) {
      combine(predefined, vars.browser);
      combine(predefined, vars.typed);
    }

    if (state.option.browserify) {
      combine(predefined, vars.browser);
      combine(predefined, vars.typed);
      combine(predefined, vars.browserify);
    }

    if (state.option.nonstandard) {
      combine(predefined, vars.nonstandard);
    }

    if (state.option.jasmine) {
      combine(predefined, vars.jasmine);
    }

    if (state.option.jquery) {
      combine(predefined, vars.jquery);
    }

    if (state.option.mootools) {
      combine(predefined, vars.mootools);
    }

    if (state.option.worker) {
      combine(predefined, vars.worker);
    }

    if (state.option.wsh) {
      combine(predefined, vars.wsh);
    }

    if (state.option.yui) {
      combine(predefined, vars.yui);
    }

    if (state.option.mocha) {
      combine(predefined, vars.mocha);
    }
  }

  // Produce an error warning.
  function quit(code, token, a, b) {
    var percentage = Math.floor((token.line / state.lines.length) * 100);
    var message = messages.errors[code].desc;

    var exception = {
      name: "JSHintError",
      line: token.line,
      character: token.from,
      message: message + " (" + percentage + "% scanned).",
      raw: message,
      code: code,
      a: a,
      b: b
    };

    exception.reason = supplant(message, exception) + " (" + percentage +
      "% scanned).";

    throw exception;
  }

  function removeIgnoredMessages() {
    var ignored = state.ignoredLines;

    if (_.isEmpty(ignored)) return;
    JSHINT.errors = _.reject(JSHINT.errors, function(err) { return ignored[err.line] });
  }

  function warning(code, t, a, b, c, d) {
    var ch, l, w, msg;

    if (/^W\d{3}$/.test(code)) {
      if (state.ignored[code])
        return;

      msg = messages.warnings[code];
    } else if (/E\d{3}/.test(code)) {
      msg = messages.errors[code];
    } else if (/I\d{3}/.test(code)) {
      msg = messages.info[code];
    }

    t = t || state.tokens.next || {};
    if (t.id === "(end)") {  // `~
      t = state.tokens.curr;
    }

    l = t.line;
    ch = t.from;

    w = {
      id: "(error)",
      raw: msg.desc,
      code: msg.code,
      evidence: state.lines[l - 1] || "",
      line: l,
      character: ch,
      scope: JSHINT.scope,
      a: a,
      b: b,
      c: c,
      d: d
    };

    w.reason = supplant(msg.desc, w);
    JSHINT.errors.push(w);

    removeIgnoredMessages();

    var errors = JSHINT.errors.filter(function(e) { return /E\d{3}/.test(e.code); });
    if (errors.length >= state.option.maxerr) {
      quit("E043", t);
    }
    return w;
  }

  function warningAt(m, l, ch, a, b, c, d) {
    return warning(m, {
      line: l,
      from: ch
    }, a, b, c, d);
  }

  function error(m, t, a, b, c, d) {
    warning(m, t, a, b, c, d);
  }

  function errorAt(m, l, ch, a, b, c, d) {
    return error(m, {
      line: l,
      from: ch
    }, a, b, c, d);
  }

  // Tracking of "internal" scripts, like eval containing a static string
  function addEvalCode(elem, token) {
    JSHINT.internals.push({
      id: "(internal)",
      elem: elem,
      token: token,
      code: token.value.replace(/([^\\])(\\*)\2\\n/g, "$1\n")
    });
  }

  /**
   * Process an inline linting directive
   *
   * @param {Token} directiveToken - the directive-bearing comment token
   * @param {Token} previous - the token that preceeds the directive
   */
  function lintingDirective(directiveToken, previous) {
    var body = directiveToken.body.split(",")
      .map(function(s) { return s.trim(); });
    var predef = {};

    if (directiveToken.type === "falls through") {
      previous.caseFallsThrough = true;
      return;
    }

    if (directiveToken.type === "globals") {
      body.forEach(function(item, idx) {
        var parts = item.split(":");
        var key = parts[0].trim();

        if (key === "-" || !key.length) {
          // Ignore trailing comma
          if (idx > 0 && idx === body.length - 1) {
            return;
          }
          error("E002", directiveToken);
          return;
        }

        if (key.charAt(0) === "-") {
          key = key.slice(1);

          JSHINT.blacklist[key] = key;
          delete predefined[key];
        } else {
          predef[key] = parts.length > 1 && parts[1].trim() === "true";
        }
      });

      combine(predefined, predef);

      for (var key in predef) {
        if (_.has(predef, key)) {
          declared[key] = directiveToken;
        }
      }
    }

    if (directiveToken.type === "exported") {
      body.forEach(function(e, idx) {
        if (!e.length) {
          // Ignore trailing comma
          if (idx > 0 && idx === body.length - 1) {
            return;
          }
          error("E002", directiveToken);
          return;
        }

        state.funct["(scope)"].addExported(e);
      });
    }

    if (directiveToken.type === "members") {
      membersOnly = membersOnly || {};

      body.forEach(function(m) {
        var ch1 = m.charAt(0);
        var ch2 = m.charAt(m.length - 1);

        if (ch1 === ch2 && (ch1 === "\"" || ch1 === "'")) {
          m = m
            .substr(1, m.length - 2)
            .replace("\\\"", "\"");
        }

        membersOnly[m] = false;
      });
    }

    var numvals = [
      "maxstatements",
      "maxparams",
      "maxdepth",
      "maxcomplexity",
      "maxerr",
      "maxlen",
      "indent"
    ];

    if (directiveToken.type === "jshint" || directiveToken.type === "jslint" ||
      directiveToken.type === "jshint.unstable") {
      body.forEach(function(item) {
        var parts = item.split(":");
        var key = parts[0].trim();
        var val = parts.length > 1 ? parts[1].trim() : "";
        var numberVal;

        if (!checkOption(key, directiveToken.type !== "jshint.unstable", directiveToken)) {
          return;
        }

        if (numvals.indexOf(key) >= 0) {
          // GH988 - numeric options can be disabled by setting them to `false`
          if (val !== "false") {
            numberVal = +val;

            if (typeof numberVal !== "number" || !isFinite(numberVal) ||
              numberVal <= 0 || Math.floor(numberVal) !== numberVal) {
              error("E032", directiveToken, val);
              return;
            }

            state.option[key] = numberVal;
          } else {
            state.option[key] = key === "indent" ? 4 : false;
          }

          return;
        }

        if (key === "validthis") {
          // `validthis` is valid only within a function scope.

          if (state.funct["(global)"])
            return void error("E009");

          if (val !== "true" && val !== "false")
            return void error("E002", directiveToken);

          state.option.validthis = (val === "true");
          return;
        }

        if (key === "quotmark") {
          switch (val) {
          case "true":
          case "false":
            state.option.quotmark = (val === "true");
            break;
          case "double":
          case "single":
            state.option.quotmark = val;
            break;
          default:
            error("E002", directiveToken);
          }
          return;
        }

        if (key === "shadow") {
          switch (val) {
          case "true":
            state.option.shadow = true;
            break;
          case "outer":
            state.option.shadow = "outer";
            break;
          case "false":
          case "inner":
            state.option.shadow = "inner";
            break;
          default:
            error("E002", directiveToken);
          }
          return;
        }

        if (key === "unused") {
          switch (val) {
          case "true":
            state.option.unused = true;
            break;
          case "false":
            state.option.unused = false;
            break;
          case "vars":
          case "strict":
            state.option.unused = val;
            break;
          default:
            error("E002", directiveToken);
          }
          return;
        }

        if (key === "latedef") {
          switch (val) {
          case "true":
            state.option.latedef = true;
            break;
          case "false":
            state.option.latedef = false;
            break;
          case "nofunc":
            state.option.latedef = "nofunc";
            break;
          default:
            error("E002", directiveToken);
          }
          return;
        }

        if (key === "ignore") {
          switch (val) {
          case "line":
            state.ignoredLines[directiveToken.line] = true;
            removeIgnoredMessages();
            break;
          default:
            error("E002", directiveToken);
          }
          return;
        }

        if (key === "strict") {
          switch (val) {
          case "true":
            state.option.strict = true;
            break;
          case "false":
            state.option.strict = false;
            break;
          case "global":
          case "implied":
            state.option.strict = val;
            break;
          default:
            error("E002", directiveToken);
          }
          return;
        }

        if (key === "module") {
          /**
           * TODO: Extend this restriction to *all* "environmental" options.
           */
          if (!hasParsedCode(state.funct)) {
            error("E055", directiveToken, "module");
          }
        }

        if (key === "esversion") {
          switch (val) {
          case "3":
          case "5":
          case "6":
          case "7":
          case "8":
          case "9":
          case "10":
          case "11":
            state.option.moz = false;
            state.option.esversion = +val;
            break;
          case "2015":
          case "2016":
          case "2017":
          case "2018":
          case "2019":
          case "2020":
            state.option.moz = false;
            // Translate specification publication year to version number.
            state.option.esversion = +val - 2009;
            break;
          default:
            error("E002", directiveToken);
          }
          if (!hasParsedCode(state.funct)) {
            error("E055", directiveToken, "esversion");
          }
          return;
        }

        var match = /^([+-])(W\d{3})$/g.exec(key);
        if (match) {
          // ignore for -W..., unignore for +W...
          state.ignored[match[2]] = (match[1] === "-");
          return;
        }

        var tn;
        if (val === "true" || val === "false") {
          if (directiveToken.type === "jslint") {
            tn = options.renamed[key] || key;
            state.option[tn] = (val === "true");

            if (options.inverted[tn] !== undefined) {
              state.option[tn] = !state.option[tn];
            }
          } else if (directiveToken.type === "jshint.unstable") {
            /* istanbul ignore next */
            state.option.unstable[key] = (val === "true");
          } else {
            state.option[key] = (val === "true");
          }

          return;
        }

        error("E002", directiveToken);
      });

      applyOptions();
    }
  }

  /**
   * Return a token beyond the token available in `state.tokens.next`. If no
   * such token exists, return the "(end)" token. This function is used to
   * determine parsing strategies in cases where the value of the next token
   * does not provide sufficient information, as is the case with `for` loops,
   * e.g.:
   *
   *     for ( var i in ...
   *
   * versus:
   *
   *     for ( var i = ...
   *
   * @param {number} [p] - offset of desired token; defaults to 0
   *
   * @returns {token}
   */
  function peek(p) {
    var i = p || 0, j = lookahead.length, t;

    if (i < j) {
      return lookahead[i];
    }

    while (j <= i) {
      t = lex.token();

      // When the lexer is exhausted, this function should produce the "(end)"
      // token, even in cases where the requested token is beyond the end of
      // the input stream.
      if (!t) {
        // If the lookahead buffer is empty, the expected "(end)" token was
        // already emitted by the most recent invocation of `advance` and is
        // available as the next token.
        if (!lookahead.length) {
          return state.tokens.next;
        }

        return lookahead[j - 1];
      }

      lookahead[j] = t;
      j += 1;
    }

    return t;
  }

  function peekIgnoreEOL() {
    var i = 0;
    var t;
    do {
      t = peek(i++);
    } while (t.id === "(endline)");
    return t;
  }

  /**
   * Consume the next token.
   *
   * @param {string} [expected] - the expected value of the next token's `id`
   *                              property (in the case of punctuators) or
   *                              `value` property (in the case of identifiers
   *                              and literals); if unspecified, any token will
   *                              be accepted
   * @param {object} [relatedToken] - the token that informed the expected
   *                                  value, if any (for example: the opening
   *                                  brace when a closing brace is expected);
   *                                  used to produce more meaningful errors
   */
  function advance(expected, relatedToken) {
    var nextToken = state.tokens.next;

    if (expected && nextToken.id !== expected) {
      if (relatedToken) {
        if (nextToken.id === "(end)") {
          error("E019", relatedToken, relatedToken.id);
        } else {
          error("E020", nextToken, expected, relatedToken.id,
            relatedToken.line, nextToken.value);
        }
      } else if (nextToken.type !== "(identifier)" || nextToken.value !== expected) {
        error("E021", nextToken, expected, nextToken.value);
      }
    }

    state.tokens.prev = state.tokens.curr;
    state.tokens.curr = state.tokens.next;
    for (;;) {
      state.tokens.next = lookahead.shift() || lex.token();

      if (!state.tokens.next) { // No more tokens left, give up
        quit("E041", state.tokens.curr);
      }

      if (state.tokens.next.id === "(end)" || state.tokens.next.id === "(error)") {
        return;
      }

      if (state.tokens.next.check) {
        state.tokens.next.check();
      }

      if (state.tokens.next.isSpecial) {
        lintingDirective(state.tokens.next, state.tokens.curr);
      } else {
        if (state.tokens.next.id !== "(endline)") {
          break;
        }
      }
    }
  }

  /**
   * Determine whether a given token is an operator.
   *
   * @param {token} token
   *
   * @returns {boolean}
   */
  function isOperator(token) {
    return token.first || token.right || token.left || token.id === "yield" || token.id === "await";
  }

  function isEndOfExpr(context, curr, next) {
    if (arguments.length <= 1) {
      curr = state.tokens.curr;
      next = state.tokens.next;
    }

    if (next.id === "in" && context & prodParams.noin) {
      return true;
    }

    if (next.id === ";" || next.id === "}" || next.id === ":") {
      return true;
    }

    if (next.infix === curr.infix ||
      // Infix operators which follow `yield` should only be consumed as part
      // of the current expression if allowed by the syntactic grammar. In
      // effect, this prevents automatic semicolon insertion when `yield` is
      // followed by a newline and a comma operator (without enabling it when
      // `yield` is followed by a newline and a `[` token).
      (curr.id === "yield" && curr.rbp < next.rbp)) {
      return !sameLine(curr, next);
    }

    return false;
  }

  /**
   * The `expression` function is the heart of JSHint's parsing behaior. It is
   * based on the Pratt parser, but it extends that model with a `fud` method.
   * Short for "first null denotation," it it similar to the `nud` ("null
   * denotation") function, but it is only used on the first token of a
   * statement. This simplifies usage in statement-oriented languages like
   * JavaScript.
   *
   * .nud  Null denotation
   * .fud  First null denotation
   * .led  Left denotation
   *  lbp  Left binding power
   *  rbp  Right binding power
   *
   * They are elements of the parsing method called Top Down Operator Precedence.
   *
   * In addition to parsing, this function applies a number of linting patterns.
   *
   * @param {number} context - the parsing context (a bitfield describing
   *                           conditions of the current parsing operation
   *                           which can influence how the next tokens are
   *                           interpreted); see `prod-params.js` for more
   *                           detail)
   * @param {number} rbp - the right-binding power of the token to be consumed
   */
  function expression(context, rbp) {
    var left, isArray = false, isObject = false;
    var initial = context & prodParams.initial;
    var curr;

    context &= ~prodParams.initial;

    state.nameStack.push();

    if (state.tokens.next.id === "(end)")
      error("E006", state.tokens.curr);

    advance();

    if (initial) {
      state.funct["(verb)"] = state.tokens.curr.value;
      state.tokens.curr.beginsStmt = true;
    }

    curr = state.tokens.curr;

    if (initial && curr.fud && (!curr.useFud || curr.useFud(context))) {
      left = state.tokens.curr.fud(context);
    } else {
      if (state.tokens.curr.nud) {
        left = state.tokens.curr.nud(context, rbp);
      } else {
        error("E030", state.tokens.curr, state.tokens.curr.id);
      }

      while (rbp < state.tokens.next.lbp && !isEndOfExpr(context)) {
        isArray = state.tokens.curr.value === "Array";
        isObject = state.tokens.curr.value === "Object";

        // #527, new Foo.Array(), Foo.Array(), new Foo.Object(), Foo.Object()
        // Line breaks in IfStatement heads exist to satisfy the checkJSHint
        // "Line too long." error.
        if (left && (left.value || (left.first && left.first.value))) {
          // If the left.value is not "new", or the left.first.value is a "."
          // then safely assume that this is not "new Array()" and possibly
          // not "new Object()"...
          if (left.value !== "new" ||
            (left.first && left.first.value && left.first.value === ".")) {
            isArray = false;
            // ...In the case of Object, if the left.value and state.tokens.curr.value
            // are not equal, then safely assume that this not "new Object()"
            if (left.value !== state.tokens.curr.value) {
              isObject = false;
            }
          }
        }

        advance();

        if (isArray && state.tokens.curr.id === "(" && state.tokens.next.id === ")") {
          warning("W009", state.tokens.curr);
        }

        if (isObject && state.tokens.curr.id === "(" && state.tokens.next.id === ")") {
          warning("W010", state.tokens.curr);
        }

        if (left && state.tokens.curr.led) {
          left = state.tokens.curr.led(context, left);
        } else {
          error("E033", state.tokens.curr, state.tokens.curr.id);
        }
      }
    }

    state.nameStack.pop();

    return left;
  }


  // Functions for conformance of style.

  function sameLine(first, second) {
    return first.line === (second.startLine || second.line);
  }

  function nobreaknonadjacent(left, right) {
    if (!state.option.laxbreak && !sameLine(left, right)) {
      warning("W014", right, right.value);
    }
  }

  function nolinebreak(t) {
    if (!sameLine(t, state.tokens.next)) {
      warning("E022", t, t.value);
    }
  }

  /**
   * Validate the comma token in the "current" position of the token stream.
   *
   * @param {object} [opts]
   * @param {boolean} [opts.property] - flag indicating whether the current
   *                                    comma token is situated directly within
   *                                    an object initializer
   * @param {boolean} [opts.allowTrailing] - flag indicating whether the
   *                                         current comma token may appear
   *                                         directly before a delimiter
   *
   * @returns {boolean} flag indicating the validity of the current comma
   *                    token; `false` if the token directly causes a syntax
   *                    error, `true` otherwise
   */
  function checkComma(opts) {
    var prev = state.tokens.prev;
    var curr = state.tokens.curr;
    opts = opts || {};

    if (!sameLine(prev, curr)) {
      if (!state.option.laxcomma) {
        if (checkComma.first) {
          warning("I001", curr);
          checkComma.first = false;
        }
        warning("W014", prev, curr.value);
      }
    }

    if (state.tokens.next.identifier && !(opts.property && state.inES5())) {
      // Keywords that cannot follow a comma operator.
      switch (state.tokens.next.value) {
      case "break":
      case "case":
      case "catch":
      case "continue":
      case "default":
      case "do":
      case "else":
      case "finally":
      case "for":
      case "if":
      case "in":
      case "instanceof":
      case "return":
      case "switch":
      case "throw":
      case "try":
      case "var":
      case "let":
      case "while":
      case "with":
        error("E024", state.tokens.next, state.tokens.next.value);
        return false;
      }
    }

    if (state.tokens.next.type === "(punctuator)") {
      switch (state.tokens.next.value) {
      case "}":
      case "]":
      case ",":
      case ")":
        if (opts.allowTrailing) {
          return true;
        }

        error("E024", state.tokens.next, state.tokens.next.value);
        return false;
      }
    }
    return true;
  }

  /**
   * Factory function for creating "symbols"--objects that will be inherited by
   * tokens. The objects created by this function are stored in a symbol table
   * and set as the prototype of the tokens generated by the lexer.
   *
   * Note that this definition of "symbol" describes an implementation detail
   * of JSHint and is not related to the ECMAScript value type introduced in
   * ES2015.
   *
   * @param {string} s - the name of the token; for keywords (e.g. `void`) and
   *                     delimiters (e.g.. `[`), this is the token's text
   *                     representation; for literals (e.g. numbers) and other
   *                     "special" tokens (e.g. the end-of-file marker) this is
   *                     a parenthetical value
   * @param {number} p - the left-binding power of the token as used by the
   *                     Pratt parsing semantics
   *
   * @returns {object} - the object describing the JSHint symbol (provided to
   *                     support cases where further refinement is necessary)
   */
  function symbol(s, p) {
    var x = state.syntax[s];
    if (!x || typeof x !== "object") {
      state.syntax[s] = x = {
        id: s,
        lbp: p,
        // Symbols that accept a right-hand side do so with a binding power
        // that is commonly identical to their left-binding power. (This value
        // is relevant when determining if the grouping operator is necessary
        // to override the precedence of surrounding operators.) Because the
        // exponentiation operator's left-binding power and right-binding power
        // are distinct, the values must be encoded separately.
        rbp: p,
        value: s
      };
    }
    return x;
  }

  /**
   * Convenience function for defining delimiter symbols.
   *
   * @param {string} s - the name of the symbol
   *
   * @returns {object} - the object describing the JSHint symbol (provided to
   *                     support cases where further refinement is necessary)
   */
  function delim(s) {
    var x = symbol(s, 0);
    x.delim = true;
    return x;
  }

  /**
   * Convenience function for defining statement-denoting symbols.
   *
   * @param {string} s - the name of the symbol
   * @param {function} f - the first null denotation function for the symbol;
   *                       see the `expression` function for more detail
   *
   * @returns {object} - the object describing the JSHint symbol (provided to
   *                     support cases where further refinement is necessary)
   */
  function stmt(s, f) {
    var x = delim(s);
    x.identifier = x.reserved = true;
    x.fud = f;
    return x;
  }

  /**
   * Convenience function for defining block-statement-denoting symbols.
   *
   * A block-statement-denoting symbol is one like 'if' or 'for', which will be
   * followed by a block and will not have to end with a semicolon.
   *
   * @param {string} s - the name of the symbol
   * @param {function} - the first null denotation function for the symbol; see
   *                     the `expression` function for more detail
   *
   * @returns {object} - the object describing the JSHint symbol (provided to
   *                     support cases where further refinement is necessary)
   */
  function blockstmt(s, f) {
    var x = stmt(s, f);
    x.block = true;
    return x;
  }
  /**
   * Denote a given JSHint symbol as an identifier and a reserved keyword.
   *
   * @param {object} - a JSHint symbol value
   *
   * @returns {object} - the provided object
   */
  function reserveName(x) {
    var c = x.id.charAt(0);
    if ((c >= "a" && c <= "z") || (c >= "A" && c <= "Z")) {
      x.identifier = x.reserved = true;
    }
    return x;
  }

  /**
   * Convenience function for defining "prefix" symbols--operators that accept
   * expressions as a right-hand side.
   *
   * @param {string} s - the name of the symbol
   * @param {function} [f] - the first null denotation function for the symbol;
   *                         see the `expression` function for more detail
   *
   * @returns {object} - the object describing the JSHint symbol (provided to
   *                     support cases where further refinement is necessary)
   */
  function prefix(s, f) {
    var x = symbol(s, 150);
    reserveName(x);

    x.nud = (typeof f === "function") ? f : function(context) {
      this.arity = "unary";
      this.right = expression(context, 150);

      if (this.id === "++" || this.id === "--") {
        if (state.option.plusplus) {
          warning("W016", this, this.id);
        }

        if (this.right) {
          checkLeftSideAssign(context, this.right, this);
        }
      }

      return this;
    };

    return x;
  }

  /**
   * Convenience function for defining "type" symbols--those that describe
   * literal values.
   *
   * @param {string} s - the name of the symbol
   * @param {function} f - the first null denotation function for the symbol;
   *                       see the `expression` function for more detail
   *
   * @returns {object} - the object describing the JSHint symbol (provided to
   *                     support cases where further refinement is necessary)
   */
  function type(s, f) {
    var x = symbol(s, 0);
    x.type = s;
    x.nud = f;
    return x;
  }

  /**
   * Convenience function for defining JSHint symbols for reserved
   * keywords--those that are restricted from use as bindings (and as property
   * names in ECMAScript 3 environments).
   *
   * @param {string} s - the name of the symbol
   * @param {function} func - the first null denotation function for the
   *                          symbol; see the `expression` function for more
   *                          detail
   *
   * @returns {object} - the object describing the JSHint symbol (provided to
   *                     support cases where further refinement is necessary)
   */
  function reserve(name, func) {
    var x = type(name, func);
    x.identifier = true;
    x.reserved = true;
    return x;
  }

  /**
   * Convenience function for defining JSHint symbols for keywords that are
   * only reserved in some circumstances.
   *
   * @param {string} name - the name of the symbol
   * @param {object} [meta] - a collection of optional arguments
   * @param {function} [meta.nud] -the null denotation function for the symbol;
   *                   see the `expression` function for more detail
   * @param {boolean} [meta.es5] - `true` if the identifier is reserved
   *                               in ECMAScript 5 or later
   * @param {boolean} [meta.strictOnly] - `true` if the identifier is only
   *                                      reserved in strict mode code.
   *
   * @returns {object} - the object describing the JSHint symbol (provided to
   *                     support cases where further refinement is necessary)
   */
  function FutureReservedWord(name, meta) {
    var x = type(name, state.syntax["(identifier)"].nud);

    meta = meta || {};
    meta.isFutureReservedWord = true;

    x.value = name;
    x.identifier = true;
    x.reserved = true;
    x.meta = meta;

    return x;
  }

  /**
   * Convenience function for defining "infix" symbols--operators that require
   * operands as both "land-hand side" and "right-hand side".
   *
   * @param {string} s - the name of the symbol
   * @param {function} [f] - a function to be invoked that consumes the
   *                         right-hand side of the operator
   * @param {number} p - the left-binding power of the token as used by the
   *                     Pratt parsing semantics
   * @param {boolean} [w] - if `true`
   *
   * @returns {object} - the object describing the JSHint symbol (provided to
   *                     support cases where further refinement is necessary)
   */
  function infix(s, f, p, w) {
    var x = symbol(s, p);
    reserveName(x);
    x.infix = true;
    x.led = function(context, left) {
      if (!w) {
        nobreaknonadjacent(state.tokens.prev, state.tokens.curr);
      }
      if ((s === "in" || s === "instanceof") && left.id === "!") {
        warning("W018", left, "!");
      }
      if (typeof f === "function") {
        return f(context, left, this);
      } else {
        this.left = left;
        this.right = expression(context, p);
        return this;
      }
    };
    return x;
  }

  /**
   * Convenience function for defining the `=>` token as used in arrow
   * functions.
   *
   * @param {string} s - the name of the symbol
   *
   * @returns {object} - the object describing the JSHint symbol (provided to
   *                     support cases where further refinement is necessary)
   */
  function application(s) {
    var x = symbol(s, 42);

    x.infix = true;
    x.led = function(context, left) {
      nobreaknonadjacent(state.tokens.prev, state.tokens.curr);

      this.left = left;
      this.right = doFunction(context, { type: "arrow", loneArg: left });
      return this;
    };
    return x;
  }

  /**
   * Convenience function for defining JSHint symbols for relation operators.
   *
   * @param {string} s - the name of the symbol
   * @param {function} [f] - a function to be invoked to enforce any additional
   *                         linting rules.
   *
   * @returns {object} - the object describing the JSHint symbol (provided to
   *                     support cases where further refinement is necessary)
   */
  function relation(s, f) {
    var x = symbol(s, 100);

    x.infix = true;
    x.led = function(context, left) {
      nobreaknonadjacent(state.tokens.prev, state.tokens.curr);
      this.left = left;
      var right = this.right = expression(context, 100);

      if (isIdentifier(left, "NaN") || isIdentifier(right, "NaN")) {
        warning("W019", this);
      } else if (f) {
        f.apply(this, [context, left, right]);
      }

      if (!left || !right) {
        quit("E041", state.tokens.curr);
      }

      if (left.id === "!") {
        warning("W018", left, "!");
      }

      if (right.id === "!") {
        warning("W018", right, "!");
      }

      return this;
    };
    return x;
  }

  /**
   * Determine if a given token marks the beginning of a UnaryExpression.
   *
   * @param {object} token
   *
   * @returns {boolean}
   */
  function beginsUnaryExpression(token) {
    return token.arity === "unary" && token.id !== "++" && token.id !== "--";
  }

  var typeofValues = {};
  typeofValues.legacy = [
    // E4X extended the `typeof` operator to return "xml" for the XML and
    // XMLList types it introduced.
    // Ref: 11.3.2 The typeof Operator
    // http://www.ecma-international.org/publications/files/ECMA-ST/Ecma-357.pdf
    "xml",
    // IE<9 reports "unknown" when the `typeof` operator is applied to an
    // object existing across a COM+ bridge. In lieu of official documentation
    // (which does not exist), see:
    // http://robertnyman.com/2005/12/21/what-is-typeof-unknown/
    "unknown"
  ];
  typeofValues.es3 = [
    "undefined", "boolean", "number", "string", "function", "object",
  ];
  typeofValues.es3 = typeofValues.es3.concat(typeofValues.legacy);
  typeofValues.es6 = typeofValues.es3.concat("symbol", "bigint");

  /**
   * Validate comparisons between the result of a `typeof` expression and a
   * string literal.
   *
   * @param {token} [left] - one of the values being compared
   * @param {token} [right] - the other value being compared
   * @param {object} state - the global state object (see `state.js`)
   *
   * @returns {boolean} - `false` if the second token describes a `typeof`
   *                       expression and the first token is a string literal
   *                       whose value is never returned by that operator;
   *                       `true` otherwise
   */
  function isTypoTypeof(left, right, state) {
    var values;

    if (state.option.notypeof)
      return false;

    if (!left || !right)
      return false;

    values = state.inES6() ? typeofValues.es6 : typeofValues.es3;

    if (right.type === "(identifier)" && right.value === "typeof" && left.type === "(string)") {
      if (left.value === "bigint") {
        if (!state.inES11()) {
          warning("W119", left, "BigInt", "11");
        }

        return false;
      }

      return !_.includes(values, left.value);
    }

    return false;
  }

  /**
   * Determine if a given token describes the built-in `eval` function.
   *
   * @param {token} left
   * @param {object} state - the global state object (see `state.js`)
   *
   * @returns {boolean}
   */
  function isGlobalEval(left, state) {
    var isGlobal = false;

    // permit methods to refer to an "eval" key in their own context
    if (left.type === "this" && state.funct["(context)"] === null) {
      isGlobal = true;
    }
    // permit use of "eval" members of objects
    else if (left.type === "(identifier)") {
      if (state.option.node && left.value === "global") {
        isGlobal = true;
      }

      else if (state.option.browser && (left.value === "window" || left.value === "document")) {
        isGlobal = true;
      }
    }

    return isGlobal;
  }

  /**
   * Determine if a given token describes a property of a built-in object.
   *
   * @param {token} left
   *
   * @returns {boolean}
   */
  function findNativePrototype(left) {
    var natives = [
      "Array", "ArrayBuffer", "Boolean", "Collator", "DataView", "Date",
      "DateTimeFormat", "Error", "EvalError", "Float32Array", "Float64Array",
      "Function", "Infinity", "Intl", "Int16Array", "Int32Array", "Int8Array",
      "Iterator", "Number", "NumberFormat", "Object", "RangeError",
      "ReferenceError", "RegExp", "StopIteration", "String", "SyntaxError",
      "TypeError", "Uint16Array", "Uint32Array", "Uint8Array", "Uint8ClampedArray",
      "URIError"
    ];

    function walkPrototype(obj) {
      if (typeof obj !== "object") return;
      return obj.right === "prototype" ? obj : walkPrototype(obj.left);
    }

    function walkNative(obj) {
      while (!obj.identifier && typeof obj.left === "object")
        obj = obj.left;

      if (obj.identifier && natives.indexOf(obj.value) >= 0 &&
          state.funct["(scope)"].isPredefined(obj.value)) {
        return obj.value;
      }
    }

    var prototype = walkPrototype(left);
    if (prototype) return walkNative(prototype);
  }

  /**
   * Determine if the given token is a valid assignment target; emit errors
   * and/or warnings as appropriate
   *
   * @param {number} context - the parsing context; see `prod-params.js` for
   *                           more information
   * @param {token} left - the left hand side of the assignment
   * @param {token=} assignToken - the token for the assignment, used for
   *                               reporting
   * @param {object=} options - optional object
   * @param {boolean} options.allowDestructuring - whether to allow
   *                                               destructuring binding
   *
   * @returns {boolean} Whether the left hand side is OK
   */
  function checkLeftSideAssign(context, left, assignToken, options) {

    var allowDestructuring = options && options.allowDestructuring;

    assignToken = assignToken || left;

    if (state.option.freeze) {
      var nativeObject = findNativePrototype(left);
      if (nativeObject)
        warning("W121", left, nativeObject);
    }

    if (left.identifier && !left.isMetaProperty) {
      // The `reassign` method also calls `modify`, but we are specific in
      // order to catch function re-assignment and globals re-assignment
      state.funct["(scope)"].block.reassign(left.value, left);
    }

    if (left.id === ".") {
      if (!left.left || left.left.value === "arguments" && !state.isStrict()) {
        warning("W143", assignToken);
      }

      state.nameStack.set(state.tokens.prev);
      return true;
    } else if (left.id === "{" || left.id === "[") {
      if (!allowDestructuring || !left.destructAssign) {
        if (left.id === "{" || !left.left) {
          warning("E031", assignToken);
        } else if (left.left.value === "arguments" && !state.isStrict()) {
          warning("W143", assignToken);
        }
      }

      if (left.id === "[") {
        state.nameStack.set(left.right);
      }

      return true;
    } else if (left.identifier && !isReserved(context, left) && !left.isMetaProperty) {
      if (state.funct["(scope)"].bindingtype(left.value) === "exception") {
        warning("W022", left);
      }

      if (left.value === "eval" && state.isStrict()) {
        error("E031", assignToken);
        return false;
      } else if (left.value === "arguments") {
        if (!state.isStrict()) {
          warning("W143", assignToken);
        } else {
          error("E031", assignToken);
          return false;
        }
      }
      state.nameStack.set(left);
      return true;
    }

    error("E031", assignToken);

    return false;
  }

  /**
   * Convenience function for defining JSHint symbols for assignment operators.
   *
   * @param {string} s - the name of the symbol
   * @param {function} [f] - a function to be invoked that consumes the
   *                         right-hand side of the operator (see the `infix`
   *                         function)
   *
   * @returns {object} - the object describing the JSHint symbol (provided to
   *                     support cases where further refinement is necessary)
   */
  function assignop(s, f) {
    var x = infix(s, typeof f === "function" ? f : function(context, left, that) {
      that.left = left;

      checkLeftSideAssign(context, left, that, { allowDestructuring: true });

      that.right = expression(context, 10);

      return that;
    }, 20);

    x.exps = true;
    x.assign = true;

    return x;
  }

  /**
   * Convenience function for defining JSHint symbols for bitwise operators.
   *
   * @param {string} s - the name of the symbol
   * @param {function} [f] - the left denotation function for the symbol; see
   *                         the `expression` function for more detail
   * @param {number} p - the left-binding power of the token as used by the
   *                     Pratt parsing semantics
   *
   * @returns {object} - the object describing the JSHint symbol (provided to
   *                     support cases where further refinement is necessary)
   */
  function bitwise(s, f, p) {
    var x = symbol(s, p);
    reserveName(x);
    x.infix = true;
    x.led = (typeof f === "function") ? f : function(context, left) {
      if (state.option.bitwise) {
        warning("W016", this, this.id);
      }
      this.left = left;
      this.right = expression(context, p);
      return this;
    };
    return x;
  }

  /**
   * Convenience function for defining JSHint symbols for bitwise assignment
   * operators. See the `assignop` function for more detail.
   *
   * @param {string} s - the name of the symbol
   *
   * @returns {object} - the object describing the JSHint symbol (provided to
   *                     support cases where further refinement is necessary)
   */
  function bitwiseassignop(s) {
    symbol(s, 20).exps = true;
    return infix(s, function(context, left, that) {
      if (state.option.bitwise) {
        warning("W016", that, that.id);
      }

      checkLeftSideAssign(context, left, that);

      that.right = expression(context, 10);

      return that;
    }, 20);
  }

  /**
   * Convenience function f