tor-browser

idlharness.js (145966B)

---

/* For user documentation see docs/_writing-tests/idlharness.md */

/**
* Notes for people who want to edit this file (not just use it as a library):
*
* Most of the interesting stuff happens in the derived classes of IdlObject,
* especially IdlInterface.  The entry point for all IdlObjects is .test(),
* which is called by IdlArray.test().  An IdlObject is conceptually just
* "thing we want to run tests on", and an IdlArray is an array of IdlObjects
* with some additional data thrown in.
*
* The object model is based on what WebIDLParser.js produces, which is in turn
* based on its pegjs grammar.  If you want to figure out what properties an
* object will have from WebIDLParser.js, the best way is to look at the
* grammar:
*
*   https://github.com/darobin/webidl.js/blob/master/lib/grammar.peg
*
* So for instance:
*
*   // interface definition
*   interface
*       =   extAttrs:extendedAttributeList? S? "interface" S name:identifier w herit:ifInheritance? w "{" w mem:ifMember* w "}" w ";" w
*           { return { type: "interface", name: name, inheritance: herit, members: mem, extAttrs: extAttrs }; }
*
* This means that an "interface" object will have a .type property equal to
* the string "interface", a .name property equal to the identifier that the
* parser found, an .inheritance property equal to either null or the result of
* the "ifInheritance" production found elsewhere in the grammar, and so on.
* After each grammatical production is a JavaScript function in curly braces
* that gets called with suitable arguments and returns some JavaScript value.
*
* (Note that the version of WebIDLParser.js we use might sometimes be
* out-of-date or forked.)
*
* The members and methods of the classes defined by this file are all at least
* briefly documented, hopefully.
*/
(function(){
"use strict";
// Support subsetTestByKey from /common/subset-tests-by-key.js, but make it optional
if (!('subsetTestByKey' in self)) {
   self.subsetTestByKey = function(key, callback, ...args) {
     return callback(...args);
   }
   self.shouldRunSubTest = () => true;
}
/// Helpers ///
function constValue (cnt)
{
   if (cnt.type === "null") return null;
   if (cnt.type === "NaN") return NaN;
   if (cnt.type === "Infinity") return cnt.negative ? -Infinity : Infinity;
   if (cnt.type === "number") return +cnt.value;
   return cnt.value;
}

function minOverloadLength(overloads)
{
   // "The value of the Function object’s “length” property is
   // a Number determined as follows:
   // ". . .
   // "Return the length of the shortest argument list of the
   // entries in S."
   if (!overloads.length) {
       return 0;
   }

   return overloads.map(function(attr) {
       return attr.arguments ? attr.arguments.filter(function(arg) {
           return !arg.optional && !arg.variadic;
       }).length : 0;
   })
   .reduce(function(m, n) { return Math.min(m, n); });
}

// A helper to get the global of a Function object.  This is needed to determine
// which global exceptions the function throws will come from.
function globalOf(func)
{
   try {
       // Use the fact that .constructor for a Function object is normally the
       // Function constructor, which can be used to mint a new function in the
       // right global.
       return func.constructor("return this;")();
   } catch (e) {
   }
   // If the above fails, because someone gave us a non-function, or a function
   // with a weird proto chain or weird .constructor property, just fall back
   // to 'self'.
   return self;
}

// https://esdiscuss.org/topic/isconstructor#content-11
function isConstructor(o) {
   try {
       new (new Proxy(o, {construct: () => ({})}));
       return true;
   } catch(e) {
       return false;
   }
}

function throwOrReject(a_test, operation, fn, obj, args, message, cb)
{
   if (operation.idlType.generic !== "Promise") {
       assert_throws_js(globalOf(fn).TypeError, function() {
           fn.apply(obj, args);
       }, message);
       cb();
   } else {
       try {
           promise_rejects_js(a_test, TypeError, fn.apply(obj, args), message).then(cb, cb);
       } catch (e){
           a_test.step(function() {
               assert_unreached("Throws \"" + e + "\" instead of rejecting promise");
               cb();
           });
       }
   }
}

function awaitNCallbacks(n, cb, ctx)
{
   var counter = 0;
   return function() {
       counter++;
       if (counter >= n) {
           cb();
       }
   };
}

/// IdlHarnessError ///
// Entry point
self.IdlHarnessError = function(message)
{
   /**
    * Message to be printed as the error's toString invocation.
    */
   this.message = message;
};

IdlHarnessError.prototype = Object.create(Error.prototype);

IdlHarnessError.prototype.toString = function()
{
   return this.message;
};


/// IdlArray ///
// Entry point
self.IdlArray = function()
{
   /**
    * A map from strings to the corresponding named IdlObject, such as
    * IdlInterface or IdlException.  These are the things that test() will run
    * tests on.
    */
   this.members = {};

   /**
    * A map from strings to arrays of strings.  The keys are interface or
    * exception names, and are expected to also exist as keys in this.members
    * (otherwise they'll be ignored).  This is populated by add_objects() --
    * see documentation at the start of the file.  The actual tests will be
    * run by calling this.members[name].test_object(obj) for each obj in
    * this.objects[name].  obj is a string that will be eval'd to produce a
    * JavaScript value, which is supposed to be an object implementing the
    * given IdlObject (interface, exception, etc.).
    */
   this.objects = {};

   /**
    * When adding multiple collections of IDLs one at a time, an earlier one
    * might contain a partial interface or includes statement that depends
    * on a later one.  Save these up and handle them right before we run
    * tests.
    *
    * Both this.partials and this.includes will be the objects as parsed by
    * WebIDLParser.js, not wrapped in IdlInterface or similar.
    */
   this.partials = [];
   this.includes = [];

   /**
    * Record of skipped IDL items, in case we later realize that they are a
    * dependency (to retroactively process them).
    */
   this.skipped = new Map();
};

IdlArray.prototype.add_idls = function(raw_idls, options)
{
   /** Entry point.  See documentation at beginning of file. */
   this.internal_add_idls(WebIDL2.parse(raw_idls), options);
};

IdlArray.prototype.add_untested_idls = function(raw_idls, options)
{
   /** Entry point.  See documentation at beginning of file. */
   var parsed_idls = WebIDL2.parse(raw_idls);
   this.mark_as_untested(parsed_idls);
   this.internal_add_idls(parsed_idls, options);
};

IdlArray.prototype.mark_as_untested = function (parsed_idls)
{
   for (var i = 0; i < parsed_idls.length; i++) {
       parsed_idls[i].untested = true;
       if ("members" in parsed_idls[i]) {
           for (var j = 0; j < parsed_idls[i].members.length; j++) {
               parsed_idls[i].members[j].untested = true;
           }
       }
   }
};

IdlArray.prototype.is_excluded_by_options = function (name, options)
{
   return options &&
       (options.except && options.except.includes(name)
        || options.only && !options.only.includes(name));
};

IdlArray.prototype.add_dependency_idls = function(raw_idls, options)
{
   return this.internal_add_dependency_idls(WebIDL2.parse(raw_idls), options);
};

IdlArray.prototype.internal_add_dependency_idls = function(parsed_idls, options)
{
   const new_options = { only: [] }

   const all_deps = new Set();
   Object.values(this.members).forEach(v => {
       if (v.base) {
           all_deps.add(v.base);
       }
   });
   // Add both 'A' and 'B' for each 'A includes B' entry.
   this.includes.forEach(i => {
       all_deps.add(i.target);
       all_deps.add(i.includes);
   });
   this.partials.forEach(p => all_deps.add(p.name));
   // Add 'TypeOfType' for each "typedef TypeOfType MyType;" entry.
   Object.entries(this.members).forEach(([k, v]) => {
       if (v instanceof IdlTypedef) {
           let defs = v.idlType.union
               ? v.idlType.idlType.map(t => t.idlType)
               : [v.idlType.idlType];
           defs.forEach(d => all_deps.add(d));
       }
   });

   // Add the attribute idlTypes of all the nested members of idls.
   const attrDeps = parsedIdls => {
       return parsedIdls.reduce((deps, parsed) => {
           if (parsed.members) {
               for (const attr of Object.values(parsed.members).filter(m => m.type === 'attribute')) {
                   let attrType = attr.idlType;
                   // Check for generic members (e.g. FrozenArray<MyType>)
                   if (attrType.generic) {
                       deps.add(attrType.generic);
                       attrType = attrType.idlType;
                   }
                   deps.add(attrType.idlType);
               }
           }
           if (parsed.base in this.members) {
               attrDeps([this.members[parsed.base]]).forEach(dep => deps.add(dep));
           }
           return deps;
       }, new Set());
   };

   const testedMembers = Object.values(this.members).filter(m => !m.untested && m.members);
   attrDeps(testedMembers).forEach(dep => all_deps.add(dep));

   const testedPartials = this.partials.filter(m => !m.untested && m.members);
   attrDeps(testedPartials).forEach(dep => all_deps.add(dep));


   if (options && options.except && options.only) {
       throw new IdlHarnessError("The only and except options can't be used together.");
   }

   const defined_or_untested = name => {
       // NOTE: Deps are untested, so we're lenient, and skip re-encountered definitions.
       // e.g. for 'idl' containing A:B, B:C, C:D
       //      array.add_idls(idl, {only: ['A','B']}).
       //      array.add_dependency_idls(idl);
       // B would be encountered as tested, and encountered as a dep, so we ignore.
       return name in this.members
           || this.is_excluded_by_options(name, options);
   }
   // Maps name -> [parsed_idl, ...]
   const process = function(parsed) {
       var deps = [];
       if (parsed.name) {
           deps.push(parsed.name);
       } else if (parsed.type === "includes") {
           deps.push(parsed.target);
           deps.push(parsed.includes);
       }

       deps = deps.filter(function(name) {
           if (!name
               || name === parsed.name && defined_or_untested(name)
               || !all_deps.has(name)) {
               // Flag as skipped, if it's not already processed, so we can
               // come back to it later if we retrospectively call it a dep.
               if (name && !(name in this.members)) {
                   this.skipped.has(name)
                       ? this.skipped.get(name).push(parsed)
                       : this.skipped.set(name, [parsed]);
               }
               return false;
           }
           return true;
       }.bind(this));

       deps.forEach(function(name) {
           if (!new_options.only.includes(name)) {
               new_options.only.push(name);
           }

           const follow_up = new Set();
           for (const dep_type of ["inheritance", "includes"]) {
               if (parsed[dep_type]) {
                   const inheriting = parsed[dep_type];
                   const inheritor = parsed.name || parsed.target;
                   const deps = [inheriting];
                   // For A includes B, we can ignore A, unless B (or some of its
                   // members) is being tested.
                   if (dep_type !== "includes"
                       || inheriting in this.members && !this.members[inheriting].untested
                       || this.partials.some(function(p) {
                               return p.name === inheriting;
                           })) {
                       deps.push(inheritor);
                   }
                   for (const dep of deps) {
                       if (!new_options.only.includes(dep)) {
                           new_options.only.push(dep);
                       }
                       all_deps.add(dep);
                       follow_up.add(dep);
                   }
               }
           }

           for (const deferred of follow_up) {
               if (this.skipped.has(deferred)) {
                   const next = this.skipped.get(deferred);
                   this.skipped.delete(deferred);
                   next.forEach(process);
               }
           }
       }.bind(this));
   }.bind(this);

   for (let parsed of parsed_idls) {
       process(parsed);
   }

   this.mark_as_untested(parsed_idls);

   if (new_options.only.length) {
       this.internal_add_idls(parsed_idls, new_options);
   }
}

IdlArray.prototype.internal_add_idls = function(parsed_idls, options)
{
   /**
    * Internal helper called by add_idls() and add_untested_idls().
    *
    * parsed_idls is an array of objects that come from WebIDLParser.js's
    * "definitions" production.  The add_untested_idls() entry point
    * additionally sets an .untested property on each object (and its
    * .members) so that they'll be skipped by test() -- they'll only be
    * used for base interfaces of tested interfaces, return types, etc.
    *
    * options is a dictionary that can have an only or except member which are
    * arrays. If only is given then only members, partials and interface
    * targets listed will be added, and if except is given only those that
    * aren't listed will be added. Only one of only and except can be used.
    */

   if (options && options.only && options.except)
   {
       throw new IdlHarnessError("The only and except options can't be used together.");
   }

   var should_skip = name => {
       return this.is_excluded_by_options(name, options);
   }

   parsed_idls.forEach(function(parsed_idl)
   {
       var partial_types = [
           "interface",
           "interface mixin",
           "dictionary",
           "namespace",
       ];
       if (parsed_idl.partial && partial_types.includes(parsed_idl.type))
       {
           if (should_skip(parsed_idl.name))
           {
               return;
           }
           this.partials.push(parsed_idl);
           return;
       }

       if (parsed_idl.type == "includes")
       {
           if (should_skip(parsed_idl.target))
           {
               return;
           }
           this.includes.push(parsed_idl);
           return;
       }

       parsed_idl.array = this;
       if (should_skip(parsed_idl.name))
       {
           return;
       }
       if (parsed_idl.name in this.members)
       {
           throw new IdlHarnessError("Duplicate identifier " + parsed_idl.name);
       }

       switch(parsed_idl.type)
       {
       case "interface":
           this.members[parsed_idl.name] =
               new IdlInterface(parsed_idl, /* is_callback = */ false, /* is_mixin = */ false);
           break;

       case "interface mixin":
           this.members[parsed_idl.name] =
               new IdlInterface(parsed_idl, /* is_callback = */ false, /* is_mixin = */ true);
           break;

       case "dictionary":
           // Nothing to test, but we need the dictionary info around for type
           // checks
           this.members[parsed_idl.name] = new IdlDictionary(parsed_idl);
           break;

       case "typedef":
           this.members[parsed_idl.name] = new IdlTypedef(parsed_idl);
           break;

       case "callback":
           this.members[parsed_idl.name] = new IdlCallback(parsed_idl);
           break;

       case "enum":
           this.members[parsed_idl.name] = new IdlEnum(parsed_idl);
           break;

       case "callback interface":
           this.members[parsed_idl.name] =
               new IdlInterface(parsed_idl, /* is_callback = */ true, /* is_mixin = */ false);
           break;

       case "namespace":
           this.members[parsed_idl.name] = new IdlNamespace(parsed_idl);
           break;

       default:
           throw parsed_idl.name + ": " + parsed_idl.type + " not yet supported";
       }
   }.bind(this));
};

IdlArray.prototype.add_objects = function(dict)
{
   /** Entry point.  See documentation at beginning of file. */
   for (var k in dict)
   {
       if (k in this.objects)
       {
           this.objects[k] = this.objects[k].concat(dict[k]);
       }
       else
       {
           this.objects[k] = dict[k];
       }
   }
};

IdlArray.prototype.prevent_multiple_testing = function(name)
{
   /** Entry point.  See documentation at beginning of file. */
   this.members[name].prevent_multiple_testing = true;
};

IdlArray.prototype.is_json_type = function(type)
{
   /**
    * Checks whether type is a JSON type as per
    * https://webidl.spec.whatwg.org/#dfn-json-types
    */

   var idlType = type.idlType;

   if (type.generic == "Promise") { return false; }

   //  nullable and annotated types don't need to be handled separately,
   //  as webidl2 doesn't represent them wrapped-up (as they're described
   //  in WebIDL).

   // union and record types
   if (type.union || type.generic == "record") {
       return idlType.every(this.is_json_type, this);
   }

   // sequence types
   if (type.generic == "sequence" || type.generic == "FrozenArray") {
       return this.is_json_type(idlType[0]);
   }

   if (typeof idlType != "string") { throw new Error("Unexpected type " + JSON.stringify(idlType)); }

   switch (idlType)
   {
      //  Numeric types
      case "byte":
      case "octet":
      case "short":
      case "unsigned short":
      case "long":
      case "unsigned long":
      case "long long":
      case "unsigned long long":
      case "float":
      case "double":
      case "unrestricted float":
      case "unrestricted double":
      // boolean
      case "boolean":
      // string types
      case "DOMString":
      case "ByteString":
      case "USVString":
      // object type
      case "object":
          return true;
      case "Error":
      case "DOMException":
      case "Int8Array":
      case "Int16Array":
      case "Int32Array":
      case "Uint8Array":
      case "Uint16Array":
      case "Uint32Array":
      case "Uint8ClampedArray":
      case "BigInt64Array":
      case "BigUint64Array":
      case "Float16Array":
      case "Float32Array":
      case "Float64Array":
      case "ArrayBuffer":
      case "DataView":
      case "any":
          return false;
      default:
          var thing = this.members[idlType];
          if (!thing) { throw new Error("Type " + idlType + " not found"); }
          if (thing instanceof IdlEnum) { return true; }

          if (thing instanceof IdlTypedef) {
              return this.is_json_type(thing.idlType);
          }

          //  dictionaries where all of their members are JSON types
          if (thing instanceof IdlDictionary) {
              const map = new Map();
              for (const dict of thing.get_reverse_inheritance_stack()) {
                  for (const m of dict.members) {
                      map.set(m.name, m.idlType);
                  }
              }
              return Array.from(map.values()).every(this.is_json_type, this);
          }

          //  interface types that have a toJSON operation declared on themselves or
          //  one of their inherited interfaces.
          if (thing instanceof IdlInterface) {
              var base;
              while (thing)
              {
                  if (thing.has_to_json_regular_operation()) { return true; }
                  var mixins = this.includes[thing.name];
                  if (mixins) {
                      mixins = mixins.map(function(id) {
                          var mixin = this.members[id];
                          if (!mixin) {
                              throw new Error("Interface " + id + " not found (implemented by " + thing.name + ")");
                          }
                          return mixin;
                      }, this);
                      if (mixins.some(function(m) { return m.has_to_json_regular_operation() } )) { return true; }
                  }
                  if (!thing.base) { return false; }
                  base = this.members[thing.base];
                  if (!base) {
                      throw new Error("Interface " + thing.base + " not found (inherited by " + thing.name + ")");
                  }
                  thing = base;
              }
              return false;
          }
          return false;
   }
};

function exposure_set(object, default_set) {
   var exposed = object.extAttrs && object.extAttrs.filter(a => a.name === "Exposed");
   if (exposed && exposed.length > 1) {
       throw new IdlHarnessError(
           `Multiple 'Exposed' extended attributes on ${object.name}`);
   }

   let result = default_set || ["Window"];
   if (result && !(result instanceof Set)) {
       result = new Set(result);
   }
   if (exposed && exposed.length) {
       const { rhs } = exposed[0];
       // Could be a list or a string.
       const set =
           rhs.type === "*" ?
           [ "*" ] :
           rhs.type === "identifier-list" ?
           rhs.value.map(id => id.value) :
           [ rhs.value ];
       result = new Set(set);
   }
   if (result && result.has("*")) {
       return "*";
   }
   if (result && result.has("Worker")) {
       result.delete("Worker");
       result.add("DedicatedWorker");
       result.add("ServiceWorker");
       result.add("SharedWorker");
   }
   return result;
}

function exposed_in(globals) {
   if (globals === "*") {
       return true;
   }
   if ('Window' in self) {
       return globals.has("Window");
   }
   if ('DedicatedWorkerGlobalScope' in self &&
       self instanceof DedicatedWorkerGlobalScope) {
       return globals.has("DedicatedWorker");
   }
   if ('SharedWorkerGlobalScope' in self &&
       self instanceof SharedWorkerGlobalScope) {
       return globals.has("SharedWorker");
   }
   if ('ServiceWorkerGlobalScope' in self &&
       self instanceof ServiceWorkerGlobalScope) {
       return globals.has("ServiceWorker");
   }
   if (Object.getPrototypeOf(self) === Object.prototype) {
       // ShadowRealm - only exposed with `"*"`.
       return false;
   }
   throw new IdlHarnessError("Unexpected global object");
}

/**
* Asserts that the given error message is thrown for the given function.
* @param {string|IdlHarnessError} error Expected Error message.
* @param {Function} idlArrayFunc Function operating on an IdlArray that should throw.
*/
IdlArray.prototype.assert_throws = function(error, idlArrayFunc)
{
   try {
       idlArrayFunc.call(this, this);
   } catch (e) {
       if (e instanceof AssertionError) {
           throw e;
       }
       // Assertions for behaviour of the idlharness.js engine.
       if (error instanceof IdlHarnessError) {
           error = error.message;
       }
       if (e.message !== error) {
           throw new IdlHarnessError(`${idlArrayFunc} threw "${e}", not the expected IdlHarnessError "${error}"`);
       }
       return;
   }
   throw new IdlHarnessError(`${idlArrayFunc} did not throw the expected IdlHarnessError`);
}

IdlArray.prototype.test = function()
{
   /** Entry point.  See documentation at beginning of file. */

   // First merge in all partial definitions and interface mixins.
   this.merge_partials();
   this.merge_mixins();

   // Assert B defined for A : B
   for (const member of Object.values(this.members).filter(m => m.base)) {
       const lhs = member.name;
       const rhs = member.base;
       if (!(rhs in this.members)) throw new IdlHarnessError(`${lhs} inherits ${rhs}, but ${rhs} is undefined.`);
       const lhs_is_interface = this.members[lhs] instanceof IdlInterface;
       const rhs_is_interface = this.members[rhs] instanceof IdlInterface;
       if (rhs_is_interface != lhs_is_interface) {
           if (!lhs_is_interface) throw new IdlHarnessError(`${lhs} inherits ${rhs}, but ${lhs} is not an interface.`);
           if (!rhs_is_interface) throw new IdlHarnessError(`${lhs} inherits ${rhs}, but ${rhs} is not an interface.`);
       }
       // Check for circular dependencies.
       member.get_reverse_inheritance_stack();
   }

   Object.getOwnPropertyNames(this.members).forEach(function(memberName) {
       var member = this.members[memberName];
       if (!(member instanceof IdlInterface || member instanceof IdlNamespace)) {
           return;
       }

       var globals = exposure_set(member);
       member.exposed = exposed_in(globals);
       member.exposureSet = globals;
   }.bind(this));

   // Now run test() on every member, and test_object() for every object.
   for (var name in this.members)
   {
       this.members[name].test();
       if (name in this.objects)
       {
           const objects = this.objects[name];
           if (!objects || !Array.isArray(objects)) {
               throw new IdlHarnessError(`Invalid or empty objects for member ${name}`);
           }
           objects.forEach(function(str)
           {
               if (!this.members[name] || !(this.members[name] instanceof IdlInterface)) {
                   throw new IdlHarnessError(`Invalid object member name ${name}`);
               }
               this.members[name].test_object(str);
           }.bind(this));
       }
   }
};

IdlArray.prototype.merge_partials = function()
{
   const testedPartials = new Map();
   this.partials.forEach(function(parsed_idl)
   {
       const originalExists = parsed_idl.name in this.members
           && (this.members[parsed_idl.name] instanceof IdlInterface
               || this.members[parsed_idl.name] instanceof IdlDictionary
               || this.members[parsed_idl.name] instanceof IdlNamespace);

       // Ensure unique test name in case of multiple partials.
       let partialTestName = parsed_idl.name;
       let partialTestCount = 1;
       if (testedPartials.has(parsed_idl.name)) {
           partialTestCount += testedPartials.get(parsed_idl.name);
           partialTestName = `${partialTestName}[${partialTestCount}]`;
       }
       testedPartials.set(parsed_idl.name, partialTestCount);

       if (!self.shouldRunSubTest(partialTestName)) {
           return;
       }

       if (!parsed_idl.untested) {
           test(function () {
               assert_true(originalExists, `Original ${parsed_idl.type} should be defined`);

               var expected;
               switch (parsed_idl.type) {
                   case 'dictionary': expected = IdlDictionary; break;
                   case 'namespace': expected = IdlNamespace; break;
                   case 'interface':
                   case 'interface mixin':
                   default:
                       expected = IdlInterface; break;
               }
               assert_true(
                   expected.prototype.isPrototypeOf(this.members[parsed_idl.name]),
                   `Original ${parsed_idl.name} definition should have type ${parsed_idl.type}`);
           }.bind(this), `Partial ${parsed_idl.type} ${partialTestName}: original ${parsed_idl.type} defined`);
       }
       if (!originalExists) {
           // Not good.. but keep calm and carry on.
           return;
       }

       if (parsed_idl.extAttrs)
       {
           // Special-case "Exposed". Must be a subset of original interface's exposure.
           // Exposed on a partial is the equivalent of having the same Exposed on all nested members.
           // See https://github.com/heycam/webidl/issues/154 for discrepency between Exposed and
           // other extended attributes on partial interfaces.
           const exposureAttr = parsed_idl.extAttrs.find(a => a.name === "Exposed");
           if (exposureAttr) {
               if (!parsed_idl.untested) {
                   test(function () {
                       const partialExposure = exposure_set(parsed_idl);
                       const memberExposure = exposure_set(this.members[parsed_idl.name]);
                       if (memberExposure === "*") {
                           return;
                       }
                       if (partialExposure === "*") {
                           throw new IdlHarnessError(
                               `Partial ${parsed_idl.name} ${parsed_idl.type} is exposed everywhere, the original ${parsed_idl.type} is not.`);
                       }
                       partialExposure.forEach(name => {
                           if (!memberExposure || !memberExposure.has(name)) {
                               throw new IdlHarnessError(
                                   `Partial ${parsed_idl.name} ${parsed_idl.type} is exposed to '${name}', the original ${parsed_idl.type} is not.`);
                           }
                       });
                   }.bind(this), `Partial ${parsed_idl.type} ${partialTestName}: valid exposure set`);
               }
               parsed_idl.members.forEach(function (member) {
                   member.extAttrs.push(exposureAttr);
               }.bind(this));
           }

           parsed_idl.extAttrs.forEach(function(extAttr)
           {
               // "Exposed" already handled above.
               if (extAttr.name === "Exposed") {
                   return;
               }
               this.members[parsed_idl.name].extAttrs.push(extAttr);
           }.bind(this));
       }
       if (parsed_idl.members.length) {
           test(function () {
               var clash = parsed_idl.members.find(function(member) {
                   return this.members[parsed_idl.name].members.find(function(m) {
                       return this.are_duplicate_members(m, member);
                   }.bind(this));
               }.bind(this));
               parsed_idl.members.forEach(function(member)
               {
                   this.members[parsed_idl.name].members.push(new IdlInterfaceMember(member));
               }.bind(this));
               assert_true(!clash, "member " + (clash && clash.name) + " is unique");
           }.bind(this), `Partial ${parsed_idl.type} ${partialTestName}: member names are unique`);
       }
   }.bind(this));
   this.partials = [];
}

IdlArray.prototype.merge_mixins = function()
{
   for (const parsed_idl of this.includes)
   {
       const lhs = parsed_idl.target;
       const rhs = parsed_idl.includes;
       const testName = lhs + " includes " + rhs + ": member names are unique";

       var errStr = lhs + " includes " + rhs + ", but ";
       if (!(lhs in this.members)) throw errStr + lhs + " is undefined.";
       if (!(this.members[lhs] instanceof IdlInterface)) throw errStr + lhs + " is not an interface.";
       if (!(rhs in this.members)) throw errStr + rhs + " is undefined.";
       if (!(this.members[rhs] instanceof IdlInterface)) throw errStr + rhs + " is not an interface.";

       if (this.members[rhs].members.length && self.shouldRunSubTest(testName)) {
           test(function () {
               var clash = this.members[rhs].members.find(function(member) {
                   return this.members[lhs].members.find(function(m) {
                       return this.are_duplicate_members(m, member);
                   }.bind(this));
               }.bind(this));
               this.members[rhs].members.forEach(function(member) {
                   assert_true(
                       this.members[lhs].members.every(m => !this.are_duplicate_members(m, member)),
                       "member " + member.name + " is unique");
                   this.members[lhs].members.push(new IdlInterfaceMember(member));
               }.bind(this));
               assert_true(!clash, "member " + (clash && clash.name) + " is unique");
           }.bind(this), testName);
       }
   }
   this.includes = [];
}

IdlArray.prototype.are_duplicate_members = function(m1, m2) {
   if (m1.name !== m2.name) {
       return false;
   }
   if (m1.type === 'operation' && m2.type === 'operation'
       && m1.arguments.length !== m2.arguments.length) {
       // Method overload. TODO: Deep comparison of arguments.
       return false;
   }
   return true;
}

IdlArray.prototype.assert_type_is = function(value, type)
{
   if (type.idlType in this.members
   && this.members[type.idlType] instanceof IdlTypedef) {
       this.assert_type_is(value, this.members[type.idlType].idlType);
       return;
   }

   if (type.nullable && value === null)
   {
       // This is fine
       return;
   }

   if (type.union) {
       for (var i = 0; i < type.idlType.length; i++) {
           try {
               this.assert_type_is(value, type.idlType[i]);
               // No AssertionError, so we match one type in the union
               return;
           } catch(e) {
               if (e instanceof AssertionError) {
                   // We didn't match this type, let's try some others
                   continue;
               }
               throw e;
           }
       }
       // TODO: Is there a nice way to list the union's types in the message?
       assert_true(false, "Attribute has value " + format_value(value)
                   + " which doesn't match any of the types in the union");

   }

   /**
    * Helper function that tests that value is an instance of type according
    * to the rules of WebIDL.  value is any JavaScript value, and type is an
    * object produced by WebIDLParser.js' "type" production.  That production
    * is fairly elaborate due to the complexity of WebIDL's types, so it's
    * best to look at the grammar to figure out what properties it might have.
    */
   if (type.idlType == "any")
   {
       // No assertions to make
       return;
   }

   if (type.array)
   {
       // TODO: not supported yet
       return;
   }

   if (type.generic === "sequence" || type.generic == "ObservableArray")
   {
       assert_true(Array.isArray(value), "should be an Array");
       if (!value.length)
       {
           // Nothing we can do.
           return;
       }
       this.assert_type_is(value[0], type.idlType[0]);
       return;
   }

   if (type.generic === "Promise") {
       assert_true("then" in value, "Attribute with a Promise type should have a then property");
       // TODO: Ideally, we would check on project fulfillment
       // that we get the right type
       // but that would require making the type check async
       return;
   }

   if (type.generic === "FrozenArray") {
       assert_true(Array.isArray(value), "Value should be array");
       assert_true(Object.isFrozen(value), "Value should be frozen");
       if (!value.length)
       {
           // Nothing we can do.
           return;
       }
       this.assert_type_is(value[0], type.idlType[0]);
       return;
   }

   type = Array.isArray(type.idlType) ? type.idlType[0] : type.idlType;

   switch(type)
   {
       case "undefined":
           assert_equals(value, undefined);
           return;

       case "boolean":
           assert_equals(typeof value, "boolean");
           return;

       case "byte":
           assert_equals(typeof value, "number");
           assert_equals(value, Math.floor(value), "should be an integer");
           assert_true(-128 <= value && value <= 127, "byte " + value + " should be in range [-128, 127]");
           return;

       case "octet":
           assert_equals(typeof value, "number");
           assert_equals(value, Math.floor(value), "should be an integer");
           assert_true(0 <= value && value <= 255, "octet " + value + " should be in range [0, 255]");
           return;

       case "short":
           assert_equals(typeof value, "number");
           assert_equals(value, Math.floor(value), "should be an integer");
           assert_true(-32768 <= value && value <= 32767, "short " + value + " should be in range [-32768, 32767]");
           return;

       case "unsigned short":
           assert_equals(typeof value, "number");
           assert_equals(value, Math.floor(value), "should be an integer");
           assert_true(0 <= value && value <= 65535, "unsigned short " + value + " should be in range [0, 65535]");
           return;

       case "long":
           assert_equals(typeof value, "number");
           assert_equals(value, Math.floor(value), "should be an integer");
           assert_true(-2147483648 <= value && value <= 2147483647, "long " + value + " should be in range [-2147483648, 2147483647]");
           return;

       case "unsigned long":
           assert_equals(typeof value, "number");
           assert_equals(value, Math.floor(value), "should be an integer");
           assert_true(0 <= value && value <= 4294967295, "unsigned long " + value + " should be in range [0, 4294967295]");
           return;

       case "long long":
           assert_equals(typeof value, "number");
           return;

       case "unsigned long long":
       case "DOMTimeStamp":
           assert_equals(typeof value, "number");
           assert_true(0 <= value, "unsigned long long should be positive");
           return;

       case "float":
           assert_equals(typeof value, "number");
           assert_equals(value, Math.fround(value), "float rounded to 32-bit float should be itself");
           assert_not_equals(value, Infinity);
           assert_not_equals(value, -Infinity);
           assert_not_equals(value, NaN);
           return;

       case "DOMHighResTimeStamp":
       case "double":
           assert_equals(typeof value, "number");
           assert_not_equals(value, Infinity);
           assert_not_equals(value, -Infinity);
           assert_not_equals(value, NaN);
           return;

       case "unrestricted float":
           assert_equals(typeof value, "number");
           assert_equals(value, Math.fround(value), "unrestricted float rounded to 32-bit float should be itself");
           return;

       case "unrestricted double":
           assert_equals(typeof value, "number");
           return;

       case "DOMString":
           assert_equals(typeof value, "string");
           return;

       case "ByteString":
           assert_equals(typeof value, "string");
           assert_regexp_match(value, /^[\x00-\x7F]*$/);
           return;

       case "USVString":
           assert_equals(typeof value, "string");
           assert_regexp_match(value, /^([\x00-\ud7ff\ue000-\uffff]|[\ud800-\udbff][\udc00-\udfff])*$/);
           return;

       case "ArrayBufferView":
           assert_true(ArrayBuffer.isView(value));
           return;

       case "object":
           assert_in_array(typeof value, ["object", "function"], "wrong type: not object or function");
           return;
   }

   // This is a catch-all for any IDL type name which follows JS class
   // semantics. This includes some non-interface IDL types (e.g. Int8Array,
   // Function, ...), as well as any interface types that are not in the IDL
   // that is fed to the harness. If an IDL type does not follow JS class
   // semantics then it should go in the switch statement above. If an IDL
   // type needs full checking, then the test should include it in the IDL it
   // feeds to the harness.
   if (!(type in this.members))
   {
       assert_true(value instanceof self[type], "wrong type: not a " + type);
       return;
   }

   if (this.members[type] instanceof IdlInterface)
   {
       // We don't want to run the full
       // IdlInterface.prototype.test_instance_of, because that could result
       // in an infinite loop.  TODO: This means we don't have tests for
       // LegacyNoInterfaceObject interfaces, and we also can't test objects
       // that come from another self.
       assert_in_array(typeof value, ["object", "function"], "wrong type: not object or function");
       if (value instanceof Object
       && !this.members[type].has_extended_attribute("LegacyNoInterfaceObject")
       && type in self)
       {
           assert_true(value instanceof self[type], "instanceof " + type);
       }
   }
   else if (this.members[type] instanceof IdlEnum)
   {
       assert_equals(typeof value, "string");
   }
   else if (this.members[type] instanceof IdlDictionary)
   {
       // TODO: Test when we actually have something to test this on
   }
   else if (this.members[type] instanceof IdlCallback)
   {
       assert_equals(typeof value, "function");
   }
   else
   {
       throw new IdlHarnessError("Type " + type + " isn't an interface, callback or dictionary");
   }
};

/// IdlObject ///
function IdlObject() {}
IdlObject.prototype.test = function()
{
   /**
    * By default, this does nothing, so no actual tests are run for IdlObjects
    * that don't define any (e.g., IdlDictionary at the time of this writing).
    */
};

IdlObject.prototype.has_extended_attribute = function(name)
{
   /**
    * This is only meaningful for things that support extended attributes,
    * such as interfaces, exceptions, and members.
    */
   return this.extAttrs.some(function(o)
   {
       return o.name == name;
   });
};


/// IdlDictionary ///
// Used for IdlArray.prototype.assert_type_is
function IdlDictionary(obj)
{
   /**
    * obj is an object produced by the WebIDLParser.js "dictionary"
    * production.
    */

   /** Self-explanatory. */
   this.name = obj.name;

   /** A back-reference to our IdlArray. */
   this.array = obj.array;

   /** An array of objects produced by the "dictionaryMember" production. */
   this.members = obj.members;

   /**
    * The name (as a string) of the dictionary type we inherit from, or null
    * if there is none.
    */
   this.base = obj.inheritance;
}

IdlDictionary.prototype = Object.create(IdlObject.prototype);

IdlDictionary.prototype.get_reverse_inheritance_stack = function() {
   return IdlInterface.prototype.get_reverse_inheritance_stack.call(this);
};

/// IdlInterface ///
function IdlInterface(obj, is_callback, is_mixin)
{
   /**
    * obj is an object produced by the WebIDLParser.js "interface" production.
    */

   /** Self-explanatory. */
   this.name = obj.name;

   /** A back-reference to our IdlArray. */
   this.array = obj.array;

   /**
    * An indicator of whether we should run tests on the interface object and
    * interface prototype object. Tests on members are controlled by .untested
    * on each member, not this.
    */
   this.untested = obj.untested;

   /** An array of objects produced by the "ExtAttr" production. */
   this.extAttrs = obj.extAttrs;

   /** An array of IdlInterfaceMembers. */
   this.members = obj.members.map(function(m){return new IdlInterfaceMember(m); });
   if (this.has_extended_attribute("LegacyUnforgeable")) {
       this.members
           .filter(function(m) { return m.special !== "static" && (m.type == "attribute" || m.type == "operation"); })
           .forEach(function(m) { return m.isUnforgeable = true; });
   }

   /**
    * The name (as a string) of the type we inherit from, or null if there is
    * none.
    */
   this.base = obj.inheritance;

   this._is_callback = is_callback;
   this._is_mixin = is_mixin;
}
IdlInterface.prototype = Object.create(IdlObject.prototype);
IdlInterface.prototype.is_callback = function()
{
   return this._is_callback;
};

IdlInterface.prototype.is_mixin = function()
{
   return this._is_mixin;
};

IdlInterface.prototype.has_constants = function()
{
   return this.members.some(function(member) {
       return member.type === "const";
   });
};

IdlInterface.prototype.get_unscopables = function()
{
   return this.members.filter(function(member) {
       return member.isUnscopable;
   });
};

IdlInterface.prototype.is_global = function()
{
   return this.extAttrs.some(function(attribute) {
       return attribute.name === "Global";
   });
};

/**
* Value of the LegacyNamespace extended attribute, if any.
*
* https://webidl.spec.whatwg.org/#LegacyNamespace
*/
IdlInterface.prototype.get_legacy_namespace = function()
{
   var legacyNamespace = this.extAttrs.find(function(attribute) {
       return attribute.name === "LegacyNamespace";
   });
   return legacyNamespace ? legacyNamespace.rhs.value : undefined;
};

IdlInterface.prototype.get_interface_object_owner = function()
{
   var legacyNamespace = this.get_legacy_namespace();
   return legacyNamespace ? self[legacyNamespace] : self;
};

IdlInterface.prototype.should_have_interface_object = function()
{
   // "For every interface that is exposed in a given ECMAScript global
   // environment and:
   // * is a callback interface that has constants declared on it, or
   // * is a non-callback interface that is not declared with the
   //   [LegacyNoInterfaceObject] extended attribute,
   // a corresponding property MUST exist on the ECMAScript global object.

   return this.is_callback() ? this.has_constants() : !this.has_extended_attribute("LegacyNoInterfaceObject");
};

IdlInterface.prototype.assert_interface_object_exists = function()
{
   var owner = this.get_legacy_namespace() || "self";
   assert_own_property(self[owner], this.name, owner + " does not have own property " + format_value(this.name));
};

IdlInterface.prototype.get_interface_object = function() {
   if (!this.should_have_interface_object()) {
       var reason = this.is_callback() ? "lack of declared constants" : "declared [LegacyNoInterfaceObject] attribute";
       throw new IdlHarnessError(this.name + " has no interface object due to " + reason);
   }

   return this.get_interface_object_owner()[this.name];
};

IdlInterface.prototype.get_qualified_name = function() {
   // https://webidl.spec.whatwg.org/#qualified-name
   var legacyNamespace = this.get_legacy_namespace();
   if (legacyNamespace) {
       return legacyNamespace + "." + this.name;
   }
   return this.name;
};

IdlInterface.prototype.has_to_json_regular_operation = function() {
   return this.members.some(function(m) {
       return m.is_to_json_regular_operation();
   });
};

IdlInterface.prototype.has_default_to_json_regular_operation = function() {
   return this.members.some(function(m) {
       return m.is_to_json_regular_operation() && m.has_extended_attribute("Default");
   });
};

/**
* Implementation of https://webidl.spec.whatwg.org/#create-an-inheritance-stack
* with the order reversed.
*
* The order is reversed so that the base class comes first in the list, because
* this is what all call sites need.
*
* So given:
*
*   A : B {};
*   B : C {};
*   C {};
*
* then A.get_reverse_inheritance_stack() returns [C, B, A],
* and B.get_reverse_inheritance_stack() returns [C, B].
*
* Note: as dictionary inheritance is expressed identically by the AST,
* this works just as well for getting a stack of inherited dictionaries.
*/
IdlInterface.prototype.get_reverse_inheritance_stack = function() {
   const stack = [this];
   let idl_interface = this;
   while (idl_interface.base) {
       const base = this.array.members[idl_interface.base];
       if (!base) {
           throw new Error(idl_interface.type + " " + idl_interface.base + " not found (inherited by " + idl_interface.name + ")");
       } else if (stack.indexOf(base) > -1) {
           stack.unshift(base);
           const dep_chain = stack.map(i => i.name).join(',');
           throw new IdlHarnessError(`${this.name} has a circular dependency: ${dep_chain}`);
       }
       idl_interface = base;
       stack.unshift(idl_interface);
   }
   return stack;
};

/**
* Implementation of
* https://webidl.spec.whatwg.org/#default-tojson-operation
* for testing purposes.
*
* Collects the IDL types of the attributes that meet the criteria
* for inclusion in the default toJSON operation for easy
* comparison with actual value
*/
IdlInterface.prototype.default_to_json_operation = function() {
   const map = new Map()
   let isDefault = false;
   for (const I of this.get_reverse_inheritance_stack()) {
       if (I.has_default_to_json_regular_operation()) {
           isDefault = true;
           for (const m of I.members) {
               if (!m.untested && m.special !== "static" && m.type == "attribute" && I.array.is_json_type(m.idlType)) {
                   map.set(m.name, m.idlType);
               }
           }
       } else if (I.has_to_json_regular_operation()) {
           isDefault = false;
       }
   }
   return isDefault ? map : null;
};

IdlInterface.prototype.test = function()
{
   if (this.has_extended_attribute("LegacyNoInterfaceObject") || this.is_mixin())
   {
       // No tests to do without an instance.  TODO: We should still be able
       // to run tests on the prototype object, if we obtain one through some
       // other means.
       return;
   }

   // If the interface object is not exposed, only test that. Members can't be
   // tested either, but objects could still be tested in |test_object|.
   if (!this.exposed)
   {
       if (!this.untested)
       {
           subsetTestByKey(this.name, test, function() {
               assert_false(this.name in self, this.name + " interface should not exist");
           }.bind(this), this.name + " interface: existence and properties of interface object");
       }
       return;
   }

   if (!this.untested)
   {
       // First test things to do with the exception/interface object and
       // exception/interface prototype object.
       this.test_self();
   }
   // Then test things to do with its members (constants, fields, attributes,
   // operations, . . .).  These are run even if .untested is true, because
   // members might themselves be marked as .untested.  This might happen to
   // interfaces if the interface itself is untested but a partial interface
   // that extends it is tested -- then the interface itself and its initial
   // members will be marked as untested, but the members added by the partial
   // interface are still tested.
   this.test_members();
};

IdlInterface.prototype.constructors = function()
{
   return this.members
       .filter(function(m) { return m.type == "constructor"; });
}

IdlInterface.prototype.test_self = function()
{
   subsetTestByKey(this.name, test, function()
   {
       if (!this.should_have_interface_object()) {
           return;
       }

       // The name of the property is the identifier of the interface, and its
       // value is an object called the interface object.
       // The property has the attributes { [[Writable]]: true,
       // [[Enumerable]]: false, [[Configurable]]: true }."
       // TODO: Should we test here that the property is actually writable
       // etc., or trust getOwnPropertyDescriptor?
       this.assert_interface_object_exists();
       var desc = Object.getOwnPropertyDescriptor(this.get_interface_object_owner(), this.name);
       assert_false("get" in desc, "self's property " + format_value(this.name) + " should not have a getter");
       assert_false("set" in desc, "self's property " + format_value(this.name) + " should not have a setter");
       assert_true(desc.writable, "self's property " + format_value(this.name) + " should be writable");
       assert_false(desc.enumerable, "self's property " + format_value(this.name) + " should not be enumerable");
       assert_true(desc.configurable, "self's property " + format_value(this.name) + " should be configurable");

       if (this.is_callback()) {
           // "The internal [[Prototype]] property of an interface object for
           // a callback interface must be the Function.prototype object."
           assert_equals(Object.getPrototypeOf(this.get_interface_object()), Function.prototype,
                         "prototype of self's property " + format_value(this.name) + " is not Object.prototype");

           return;
       }

       // "The interface object for a given non-callback interface is a
       // function object."
       // "If an object is defined to be a function object, then it has
       // characteristics as follows:"

       // Its [[Prototype]] internal property is otherwise specified (see
       // below).

       // "* Its [[Get]] internal property is set as described in ECMA-262
       //    section 9.1.8."
       // Not much to test for this.

       // "* Its [[Construct]] internal property is set as described in
       //    ECMA-262 section 19.2.2.3."

       // "* Its @@hasInstance property is set as described in ECMA-262
       //    section 19.2.3.8, unless otherwise specified."
       // TODO

       // ES6 (rev 30) 19.1.3.6:
       // "Else, if O has a [[Call]] internal method, then let builtinTag be
       // "Function"."
       assert_class_string(this.get_interface_object(), "Function", "class string of " + this.name);

       // "The [[Prototype]] internal property of an interface object for a
       // non-callback interface is determined as follows:"
       var prototype = Object.getPrototypeOf(this.get_interface_object());
       if (this.base) {
           // "* If the interface inherits from some other interface, the
           //    value of [[Prototype]] is the interface object for that other
           //    interface."
           var inherited_interface = this.array.members[this.base];
           if (!inherited_interface.has_extended_attribute("LegacyNoInterfaceObject")) {
               inherited_interface.assert_interface_object_exists();
               assert_equals(prototype, inherited_interface.get_interface_object(),
                             'prototype of ' + this.name + ' is not ' +
                             this.base);
           }
       } else {
           // "If the interface doesn't inherit from any other interface, the
           // value of [[Prototype]] is %FunctionPrototype% ([ECMA-262],
           // section 6.1.7.4)."
           assert_equals(prototype, Function.prototype,
                         "prototype of self's property " + format_value(this.name) + " is not Function.prototype");
       }

       // Always test for [[Construct]]:
       // https://github.com/heycam/webidl/issues/698
       assert_true(isConstructor(this.get_interface_object()), "interface object must pass IsConstructor check");

       var interface_object = this.get_interface_object();
       assert_throws_js(globalOf(interface_object).TypeError, function() {
           interface_object();
       }, "interface object didn't throw TypeError when called as a function");

       if (!this.constructors().length) {
           assert_throws_js(globalOf(interface_object).TypeError, function() {
               new interface_object();
           }, "interface object didn't throw TypeError when called as a constructor");
       }
   }.bind(this), this.name + " interface: existence and properties of interface object");

   if (this.should_have_interface_object() && !this.is_callback()) {
       subsetTestByKey(this.name, test, function() {
           // This function tests WebIDL as of 2014-10-25.
           // https://webidl.spec.whatwg.org/#es-interface-call

           this.assert_interface_object_exists();

           // "Interface objects for non-callback interfaces MUST have a
           // property named “length” with attributes { [[Writable]]: false,
           // [[Enumerable]]: false, [[Configurable]]: true } whose value is
           // a Number."
           assert_own_property(this.get_interface_object(), "length");
           var desc = Object.getOwnPropertyDescriptor(this.get_interface_object(), "length");
           assert_false("get" in desc, this.name + ".length should not have a getter");
           assert_false("set" in desc, this.name + ".length should not have a setter");
           assert_false(desc.writable, this.name + ".length should not be writable");
           assert_false(desc.enumerable, this.name + ".length should not be enumerable");
           assert_true(desc.configurable, this.name + ".length should be configurable");

           var constructors = this.constructors();
           var expected_length = minOverloadLength(constructors);
           assert_equals(this.get_interface_object().length, expected_length, "wrong value for " + this.name + ".length");
       }.bind(this), this.name + " interface object length");
   }

   if (this.should_have_interface_object()) {
       subsetTestByKey(this.name, test, function() {
           // This function tests WebIDL as of 2015-11-17.
           // https://webidl.spec.whatwg.org/#interface-object

           this.assert_interface_object_exists();

           // "All interface objects must have a property named “name” with
           // attributes { [[Writable]]: false, [[Enumerable]]: false,
           // [[Configurable]]: true } whose value is the identifier of the
           // corresponding interface."

           assert_own_property(this.get_interface_object(), "name");
           var desc = Object.getOwnPropertyDescriptor(this.get_interface_object(), "name");
           assert_false("get" in desc, this.name + ".name should not have a getter");
           assert_false("set" in desc, this.name + ".name should not have a setter");
           assert_false(desc.writable, this.name + ".name should not be writable");
           assert_false(desc.enumerable, this.name + ".name should not be enumerable");
           assert_true(desc.configurable, this.name + ".name should be configurable");
           assert_equals(this.get_interface_object().name, this.name, "wrong value for " + this.name + ".name");
       }.bind(this), this.name + " interface object name");
   }


   if (this.has_extended_attribute("LegacyWindowAlias")) {
       subsetTestByKey(this.name, test, function()
       {
           var aliasAttrs = this.extAttrs.filter(function(o) { return o.name === "LegacyWindowAlias"; });
           if (aliasAttrs.length > 1) {
               throw new IdlHarnessError("Invalid IDL: multiple LegacyWindowAlias extended attributes on " + this.name);
           }
           if (this.is_callback()) {
               throw new IdlHarnessError("Invalid IDL: LegacyWindowAlias extended attribute on non-interface " + this.name);
           }
           if (!(this.exposureSet === "*" || this.exposureSet.has("Window"))) {
               throw new IdlHarnessError("Invalid IDL: LegacyWindowAlias extended attribute on " + this.name + " which is not exposed in Window");
           }
           // TODO: when testing of [LegacyNoInterfaceObject] interfaces is supported,
           // check that it's not specified together with LegacyWindowAlias.

           // TODO: maybe check that [LegacyWindowAlias] is not specified on a partial interface.

           var rhs = aliasAttrs[0].rhs;
           if (!rhs) {
               throw new IdlHarnessError("Invalid IDL: LegacyWindowAlias extended attribute on " + this.name + " without identifier");
           }
           var aliases;
           if (rhs.type === "identifier-list") {
               aliases = rhs.value.map(id => id.value);
           } else { // rhs.type === identifier
               aliases = [ rhs.value ];
           }

           // OK now actually check the aliases...
           var alias;
           if (exposed_in(exposure_set(this, this.exposureSet)) && 'document' in self) {
               for (alias of aliases) {
                   assert_true(alias in self, alias + " should exist");
                   assert_equals(self[alias], this.get_interface_object(), "self." + alias + " should be the same value as self." + this.get_qualified_name());
                   var desc = Object.getOwnPropertyDescriptor(self, alias);
                   assert_equals(desc.value, this.get_interface_object(), "wrong value in " + alias + " property descriptor");
                   assert_true(desc.writable, alias + " should be writable");
                   assert_false(desc.enumerable, alias + " should not be enumerable");
                   assert_true(desc.configurable, alias + " should be configurable");
                   assert_false('get' in desc, alias + " should not have a getter");
                   assert_false('set' in desc, alias + " should not have a setter");
               }
           } else {
               for (alias of aliases) {
                   assert_false(alias in self, alias + " should not exist");
               }
           }

       }.bind(this), this.name + " interface: legacy window alias");
   }

   if (this.has_extended_attribute("LegacyFactoryFunction")) {
       var constructors = this.extAttrs
           .filter(function(attr) { return attr.name == "LegacyFactoryFunction"; });
       if (constructors.length !== 1) {
           throw new IdlHarnessError("Internal error: missing support for multiple LegacyFactoryFunction extended attributes");
       }
       var constructor = constructors[0];
       var min_length = minOverloadLength([constructor]);

       subsetTestByKey(this.name, test, function()
       {
           // This function tests WebIDL as of 2019-01-14.

           // "for every [LegacyFactoryFunction] extended attribute on an exposed
           // interface, a corresponding property must exist on the ECMAScript
           // global object. The name of the property is the
           // [LegacyFactoryFunction]'s identifier, and its value is an object
           // called a named constructor, ... . The property has the attributes
           // { [[Writable]]: true, [[Enumerable]]: false,
           // [[Configurable]]: true }."
           var name = constructor.rhs.value;
           assert_own_property(self, name);
           var desc = Object.getOwnPropertyDescriptor(self, name);
           assert_equals(desc.value, self[name], "wrong value in " + name + " property descriptor");
           assert_true(desc.writable, name + " should be writable");
           assert_false(desc.enumerable, name + " should not be enumerable");
           assert_true(desc.configurable, name + " should be configurable");
           assert_false("get" in desc, name + " should not have a getter");
           assert_false("set" in desc, name + " should not have a setter");
       }.bind(this), this.name + " interface: named constructor");

       subsetTestByKey(this.name, test, function()
       {
           // This function tests WebIDL as of 2019-01-14.

           // "2. Let F be ! CreateBuiltinFunction(realm, steps,
           //     realm.[[Intrinsics]].[[%FunctionPrototype%]])."
           var name = constructor.rhs.value;
           var value = self[name];
           assert_equals(typeof value, "function", "type of value in " + name + " property descriptor");
           assert_not_equals(value, this.get_interface_object(), "wrong value in " + name + " property descriptor");
           assert_equals(Object.getPrototypeOf(value), Function.prototype, "wrong value for " + name + "'s prototype");
       }.bind(this), this.name + " interface: named constructor object");

       subsetTestByKey(this.name, test, function()
       {
           // This function tests WebIDL as of 2019-01-14.

           // "7. Let proto be the interface prototype object of interface I
           //     in realm.
           // "8. Perform ! DefinePropertyOrThrow(F, "prototype",
           //     PropertyDescriptor{
           //         [[Value]]: proto, [[Writable]]: false,
           //         [[Enumerable]]: false, [[Configurable]]: false
           //     })."
           var name = constructor.rhs.value;
           var expected = this.get_interface_object().prototype;
           var desc = Object.getOwnPropertyDescriptor(self[name], "prototype");
           assert_equals(desc.value, expected, "wrong value for " + name + ".prototype");
           assert_false(desc.writable, "prototype should not be writable");
           assert_false(desc.enumerable, "prototype should not be enumerable");
           assert_false(desc.configurable, "prototype should not be configurable");
           assert_false("get" in desc, "prototype should not have a getter");
           assert_false("set" in desc, "prototype should not have a setter");
       }.bind(this), this.name + " interface: named constructor prototype property");

       subsetTestByKey(this.name, test, function()
       {
           // This function tests WebIDL as of 2019-01-14.

           // "3. Perform ! SetFunctionName(F, id)."
           var name = constructor.rhs.value;
           var desc = Object.getOwnPropertyDescriptor(self[name], "name");
           assert_equals(desc.value, name, "wrong value for " + name + ".name");
           assert_false(desc.writable, "name should not be writable");
           assert_false(desc.enumerable, "name should not be enumerable");
           assert_true(desc.configurable, "name should be configurable");
           assert_false("get" in desc, "name should not have a getter");
           assert_false("set" in desc, "name should not have a setter");
       }.bind(this), this.name + " interface: named constructor name");

       subsetTestByKey(this.name, test, function()
       {
           // This function tests WebIDL as of 2019-01-14.

           // "4. Initialize S to the effective overload set for constructors
           //     with identifier id on interface I and with argument count 0.
           // "5. Let length be the length of the shortest argument list of
           //     the entries in S.
           // "6. Perform ! SetFunctionLength(F, length)."
           var name = constructor.rhs.value;
           var desc = Object.getOwnPropertyDescriptor(self[name], "length");
           assert_equals(desc.value, min_length, "wrong value for " + name + ".length");
           assert_false(desc.writable, "length should not be writable");
           assert_false(desc.enumerable, "length should not be enumerable");
           assert_true(desc.configurable, "length should be configurable");
           assert_false("get" in desc, "length should not have a getter");
           assert_false("set" in desc, "length should not have a setter");
       }.bind(this), this.name + " interface: named constructor length");

       subsetTestByKey(this.name, test, function()
       {
           // This function tests WebIDL as of 2019-01-14.

           // "1. Let steps be the following steps:
           // "    1. If NewTarget is undefined, then throw a TypeError."
           var name = constructor.rhs.value;
           var args = constructor.arguments.map(function(arg) {
               return create_suitable_object(arg.idlType);
           });
           assert_throws_js(globalOf(self[name]).TypeError, function() {
               self[name](...args);
           }.bind(this));
       }.bind(this), this.name + " interface: named constructor without 'new'");
   }

   subsetTestByKey(this.name, test, function()
   {
       // This function tests WebIDL as of 2015-01-21.
       // https://webidl.spec.whatwg.org/#interface-object

       if (!this.should_have_interface_object()) {
           return;
       }

       this.assert_interface_object_exists();

       if (this.is_callback()) {
           assert_false("prototype" in this.get_interface_object(),
                        this.name + ' should not have a "prototype" property');
           return;
       }

       // "An interface object for a non-callback interface must have a
       // property named “prototype” with attributes { [[Writable]]: false,
       // [[Enumerable]]: false, [[Configurable]]: false } whose value is an
       // object called the interface prototype object. This object has
       // properties that correspond to the regular attributes and regular
       // operations defined on the interface, and is described in more detail
       // in section 4.5.4 below."
       assert_own_property(this.get_interface_object(), "prototype",
                           'interface "' + this.name + '" does not have own property "prototype"');
       var desc = Object.getOwnPropertyDescriptor(this.get_interface_object(), "prototype");
       assert_false("get" in desc, this.name + ".prototype should not have a getter");
       assert_false("set" in desc, this.name + ".prototype should not have a setter");
       assert_false(desc.writable, this.name + ".prototype should not be writable");
       assert_false(desc.enumerable, this.name + ".prototype should not be enumerable");
       assert_false(desc.configurable, this.name + ".prototype should not be configurable");

       // Next, test that the [[Prototype]] of the interface prototype object
       // is correct. (This is made somewhat difficult by the existence of
       // [LegacyNoInterfaceObject].)
       // TODO: Aryeh thinks there's at least other place in this file where
       //       we try to figure out if an interface prototype object is
       //       correct. Consolidate that code.

       // "The interface prototype object for a given interface A must have an
       // internal [[Prototype]] property whose value is returned from the
       // following steps:
       // "If A is declared with the [Global] extended
       // attribute, and A supports named properties, then return the named
       // properties object for A, as defined in §3.6.4 Named properties
       // object.
       // "Otherwise, if A is declared to inherit from another interface, then
       // return the interface prototype object for the inherited interface.
       // "Otherwise, return %ObjectPrototype%.
       //
       // "In the ECMAScript binding, the DOMException type has some additional
       // requirements:
       //
       //     "Unlike normal interface types, the interface prototype object
       //     for DOMException must have as its [[Prototype]] the intrinsic
       //     object %ErrorPrototype%."
       //
       if (this.name === "Window") {
           assert_class_string(Object.getPrototypeOf(this.get_interface_object().prototype),
                               'WindowProperties',
                               'Class name for prototype of Window' +
                               '.prototype is not "WindowProperties"');
       } else {
           var inherit_interface, inherit_interface_interface_object;
           if (this.base) {
               inherit_interface = this.base;
               var parent = this.array.members[inherit_interface];
               if (!parent.has_extended_attribute("LegacyNoInterfaceObject")) {
                   parent.assert_interface_object_exists();
                   inherit_interface_interface_object = parent.get_interface_object();
               }
           } else if (this.name === "DOMException") {
               inherit_interface = 'Error';
               inherit_interface_interface_object = self.Error;
           } else {
               inherit_interface = 'Object';
               inherit_interface_interface_object = self.Object;
           }
           if (inherit_interface_interface_object) {
               assert_not_equals(inherit_interface_interface_object, undefined,
                                 'should inherit from ' + inherit_interface + ', but there is no such property');
               assert_own_property(inherit_interface_interface_object, 'prototype',
                                   'should inherit from ' + inherit_interface + ', but that object has no "prototype" property');
               assert_equals(Object.getPrototypeOf(this.get_interface_object().prototype),
                             inherit_interface_interface_object.prototype,
                             'prototype of ' + this.name + '.prototype is not ' + inherit_interface + '.prototype');
           } else {
               // We can't test that we get the correct object, because this is the
               // only way to get our hands on it. We only test that its class
               // string, at least, is correct.
               assert_class_string(Object.getPrototypeOf(this.get_interface_object().prototype),
                                   inherit_interface + 'Prototype',
                                   'Class name for prototype of ' + this.name +
                                   '.prototype is not "' + inherit_interface + 'Prototype"');
           }
       }

       // "The class string of an interface prototype object is the
       // concatenation of the interface’s qualified identifier and the string
       // “Prototype”."

       // Skip these tests for now due to a specification issue about
       // prototype name.
       // https://www.w3.org/Bugs/Public/show_bug.cgi?id=28244

       // assert_class_string(this.get_interface_object().prototype, this.get_qualified_name() + "Prototype",
       //                     "class string of " + this.name + ".prototype");

       // String() should end up calling {}.toString if nothing defines a
       // stringifier.
       if (!this.has_stringifier()) {
           // assert_equals(String(this.get_interface_object().prototype), "[object " + this.get_qualified_name() + "Prototype]",
           //         "String(" + this.name + ".prototype)");
       }
   }.bind(this), this.name + " interface: existence and properties of interface prototype object");

   // "If the interface is declared with the [Global]
   // extended attribute, or the interface is in the set of inherited
   // interfaces for any other interface that is declared with one of these
   // attributes, then the interface prototype object must be an immutable
   // prototype exotic object."
   // https://webidl.spec.whatwg.org/#interface-prototype-object
   if (this.is_global()) {
       this.test_immutable_prototype("interface prototype object", this.get_interface_object().prototype);
   }

   subsetTestByKey(this.name, test, function()
   {
       if (!this.should_have_interface_object()) {
           return;
       }

       this.assert_interface_object_exists();

       if (this.is_callback()) {
           assert_false("prototype" in this.get_interface_object(),
                        this.name + ' should not have a "prototype" property');
           return;
       }

       assert_own_property(this.get_interface_object(), "prototype",
                           'interface "' + this.name + '" does not have own property "prototype"');

       // "If the [LegacyNoInterfaceObject] extended attribute was not specified
       // on the interface, then the interface prototype object must also have a
       // property named “constructor” with attributes { [[Writable]]: true,
       // [[Enumerable]]: false, [[Configurable]]: true } whose value is a
       // reference to the interface object for the interface."
       assert_own_property(this.get_interface_object().prototype, "constructor",
                           this.name + '.prototype does not have own property "constructor"');
       var desc = Object.getOwnPropertyDescriptor(this.get_interface_object().prototype, "constructor");
       assert_false("get" in desc, this.name + ".prototype.constructor should not have a getter");
       assert_false("set" in desc, this.name + ".prototype.constructor should not have a setter");
       assert_true(desc.writable, this.name + ".prototype.constructor should be writable");
       assert_false(desc.enumerable, this.name + ".prototype.constructor should not be enumerable");
       assert_true(desc.configurable, this.name + ".prototype.constructor should be configurable");
       assert_equals(this.get_interface_object().prototype.constructor, this.get_interface_object(),
                     this.name + '.prototype.constructor is not the same object as ' + this.name);
   }.bind(this), this.name + ' interface: existence and properties of interface prototype object\'s "constructor" property');


   subsetTestByKey(this.name, test, function()
   {
       if (!this.should_have_interface_object()) {
           return;
       }

       this.assert_interface_object_exists();

       if (this.is_callback()) {
           assert_false("prototype" in this.get_interface_object(),
                        this.name + ' should not have a "prototype" property');
           return;
       }

       assert_own_property(this.get_interface_object(), "prototype",
                           'interface "' + this.name + '" does not have own property "prototype"');

       // If the interface has any member declared with the [Unscopable] extended
       // attribute, then there must be a property on the interface prototype object
       // whose name is the @@unscopables symbol, which has the attributes
       // { [[Writable]]: false, [[Enumerable]]: false, [[Configurable]]: true },
       // and whose value is an object created as follows...
       var unscopables = this.get_unscopables().map(m => m.name);
       var proto = this.get_interface_object().prototype;
       if (unscopables.length != 0) {
           assert_own_property(
               proto, Symbol.unscopables,
               this.name + '.prototype should have an @@unscopables property');
           var desc = Object.getOwnPropertyDescriptor(proto, Symbol.unscopables);
           assert_false("get" in desc,
                        this.name + ".prototype[Symbol.unscopables] should not have a getter");
           assert_false("set" in desc, this.name + ".prototype[Symbol.unscopables] should not have a setter");
           assert_false(desc.writable, this.name + ".prototype[Symbol.unscopables] should not be writable");
           assert_false(desc.enumerable, this.name + ".prototype[Symbol.unscopables] should not be enumerable");
           assert_true(desc.configurable, this.name + ".prototype[Symbol.unscopables] should be configurable");
           assert_equals(desc.value, proto[Symbol.unscopables],
                         this.name + '.prototype[Symbol.unscopables] should be in the descriptor');
           assert_equals(typeof desc.value, "object",
                         this.name + '.prototype[Symbol.unscopables] should be an object');
           assert_equals(Object.getPrototypeOf(desc.value), null,
                         this.name + '.prototype[Symbol.unscopables] should have a null prototype');
           assert_equals(Object.getOwnPropertySymbols(desc.value).length,
                         0,
                         this.name + '.prototype[Symbol.unscopables] should have the right number of symbol-named properties');

           // Check that we do not have _extra_ unscopables.  Checking that we
           // have all the ones we should will happen in the per-member tests.
           var observed = Object.getOwnPropertyNames(desc.value);
           for (var prop of observed) {
               assert_not_equals(unscopables.indexOf(prop),
                                 -1,
                                 this.name + '.prototype[Symbol.unscopables] has unexpected property "' + prop + '"');
           }
       } else {
           assert_equals(Object.getOwnPropertyDescriptor(this.get_interface_object().prototype, Symbol.unscopables),
                         undefined,
                         this.name + '.prototype should not have @@unscopables');
       }
   }.bind(this), this.name + ' interface: existence and properties of interface prototype object\'s @@unscopables property');
};

IdlInterface.prototype.test_immutable_prototype = function(type, obj)
{
   if (typeof Object.setPrototypeOf !== "function") {
       return;
   }

   subsetTestByKey(this.name, test, function(t) {
       var originalValue = Object.getPrototypeOf(obj);
       var newValue = Object.create(null);

       t.add_cleanup(function() {
           try {
               Object.setPrototypeOf(obj, originalValue);
           } catch (err) {}
       });

       assert_throws_js(TypeError, function() {
           Object.setPrototypeOf(obj, newValue);
       });

       assert_equals(
               Object.getPrototypeOf(obj),
               originalValue,
               "original value not modified"
           );
   }.bind(this), this.name + " interface: internal [[SetPrototypeOf]] method " +
       "of " + type + " - setting to a new value via Object.setPrototypeOf " +
       "should throw a TypeError");

   subsetTestByKey(this.name, test, function(t) {
       var originalValue = Object.getPrototypeOf(obj);
       var newValue = Object.create(null);

       t.add_cleanup(function() {
           let setter = Object.getOwnPropertyDescriptor(
               Object.prototype, '__proto__'
           ).set;

           try {
               setter.call(obj, originalValue);
           } catch (err) {}
       });

       // We need to find the actual setter for the '__proto__' property, so we
       // can determine the right global for it.  Walk up the prototype chain
       // looking for that property until we find it.
       let setter;
       {
           let cur = obj;
           while (cur) {
               const desc = Object.getOwnPropertyDescriptor(cur, "__proto__");
               if (desc) {
                   setter = desc.set;
                   break;
               }
               cur = Object.getPrototypeOf(cur);
           }
       }
       assert_throws_js(globalOf(setter).TypeError, function() {
           obj.__proto__ = newValue;
       });

       assert_equals(
               Object.getPrototypeOf(obj),
               originalValue,
               "original value not modified"
           );
   }.bind(this), this.name + " interface: internal [[SetPrototypeOf]] method " +
       "of " + type + " - setting to a new value via __proto__ " +
       "should throw a TypeError");

   subsetTestByKey(this.name, test, function(t) {
       var originalValue = Object.getPrototypeOf(obj);
       var newValue = Object.create(null);

       t.add_cleanup(function() {
           try {
               Reflect.setPrototypeOf(obj, originalValue);
           } catch (err) {}
       });

       assert_false(Reflect.setPrototypeOf(obj, newValue));

       assert_equals(
               Object.getPrototypeOf(obj),
               originalValue,
               "original value not modified"
           );
   }.bind(this), this.name + " interface: internal [[SetPrototypeOf]] method " +
       "of " + type + " - setting to a new value via Reflect.setPrototypeOf " +
       "should return false");

   subsetTestByKey(this.name, test, function() {
       var originalValue = Object.getPrototypeOf(obj);

       Object.setPrototypeOf(obj, originalValue);
   }.bind(this), this.name + " interface: internal [[SetPrototypeOf]] method " +
       "of " + type + " - setting to its original value via Object.setPrototypeOf " +
       "should not throw");

   subsetTestByKey(this.name, test, function() {
       var originalValue = Object.getPrototypeOf(obj);

       obj.__proto__ = originalValue;
   }.bind(this), this.name + " interface: internal [[SetPrototypeOf]] method " +
       "of " + type + " - setting to its original value via __proto__ " +
       "should not throw");

   subsetTestByKey(this.name, test, function() {
       var originalValue = Object.getPrototypeOf(obj);

       assert_true(Reflect.setPrototypeOf(obj, originalValue));
   }.bind(this), this.name + " interface: internal [[SetPrototypeOf]] method " +
       "of " + type + " - setting to its original value via Reflect.setPrototypeOf " +
       "should return true");
};

IdlInterface.prototype.test_member_const = function(member)
{
   if (!this.has_constants()) {
       throw new IdlHarnessError("Internal error: test_member_const called without any constants");
   }

   subsetTestByKey(this.name, test, function()
   {
       this.assert_interface_object_exists();

       // "For each constant defined on an interface A, there must be
       // a corresponding property on the interface object, if it
       // exists."
       assert_own_property(this.get_interface_object(), member.name);
       // "The value of the property is that which is obtained by
       // converting the constant’s IDL value to an ECMAScript
       // value."
       assert_equals(this.get_interface_object()[member.name], constValue(member.value),
                     "property has wrong value");
       // "The property has attributes { [[Writable]]: false,
       // [[Enumerable]]: true, [[Configurable]]: false }."
       var desc = Object.getOwnPropertyDescriptor(this.get_interface_object(), member.name);
       assert_false("get" in desc, "property should not have a getter");
       assert_false("set" in desc, "property should not have a setter");
       assert_false(desc.writable, "property should not be writable");
       assert_true(desc.enumerable, "property should be enumerable");
       assert_false(desc.configurable, "property should not be configurable");
   }.bind(this), this.name + " interface: constant " + member.name + " on interface object");

   // "In addition, a property with the same characteristics must
   // exist on the interface prototype object."
   subsetTestByKey(this.name, test, function()
   {
       this.assert_interface_object_exists();

       if (this.is_callback()) {
           assert_false("prototype" in this.get_interface_object(),
                        this.name + ' should not have a "prototype" property');
           return;
       }

       assert_own_property(this.get_interface_object(), "prototype",
                           'interface "' + this.name + '" does not have own property "prototype"');

       assert_own_property(this.get_interface_object().prototype, member.name);
       assert_equals(this.get_interface_object().prototype[member.name], constValue(member.value),
                     "property has wrong value");
       var desc = Object.getOwnPropertyDescriptor(this.get_interface_object(), member.name);
       assert_false("get" in desc, "property should not have a getter");
       assert_false("set" in desc, "property should not have a setter");
       assert_false(desc.writable, "property should not be writable");
       assert_true(desc.enumerable, "property should be enumerable");
       assert_false(desc.configurable, "property should not be configurable");
   }.bind(this), this.name + " interface: constant " + member.name + " on interface prototype object");
};


IdlInterface.prototype.test_member_attribute = function(member)
 {
   if (!shouldRunSubTest(this.name)) {
       return;
   }
   var a_test = subsetTestByKey(this.name, async_test, this.name + " interface: attribute " + member.name);
   a_test.step(function()
   {
       if (!this.should_have_interface_object()) {
           a_test.done();
           return;
       }

       this.assert_interface_object_exists();
       assert_own_property(this.get_interface_object(), "prototype",
                           'interface "' + this.name + '" does not have own property "prototype"');

       if (member.special === "static") {
           assert_own_property(this.get_interface_object(), member.name,
               "The interface object must have a property " +
               format_value(member.name));
           a_test.done();
           return;
       }

       this.do_member_unscopable_asserts(member);

       if (this.is_global()) {
           assert_own_property(self, member.name,
               "The global object must have a property " +
               format_value(member.name));
           assert_false(member.name in this.get_interface_object().prototype,
               "The prototype object should not have a property " +
               format_value(member.name));

           var getter = Object.getOwnPropertyDescriptor(self, member.name).get;
           assert_equals(typeof(getter), "function",
                         format_value(member.name) + " must have a getter");

           // Try/catch around the get here, since it can legitimately throw.
           // If it does, we obviously can't check for equality with direct
           // invocation of the getter.
           var gotValue;
           var propVal;
           try {
               propVal = self[member.name];
               gotValue = true;
           } catch (e) {
               gotValue = false;
           }
           if (gotValue) {
               assert_equals(propVal, getter.call(undefined),
                             "Gets on a global should not require an explicit this");
           }

           // do_interface_attribute_asserts must be the last thing we do,
           // since it will call done() on a_test.
           this.do_interface_attribute_asserts(self, member, a_test);
       } else {
           assert_true(member.name in this.get_interface_object().prototype,
               "The prototype object must have a property " +
               format_value(member.name));

           if (!member.has_extended_attribute("LegacyLenientThis")) {
               if (member.idlType.generic !== "Promise") {
                   // this.get_interface_object() returns a thing in our global
                   assert_throws_js(TypeError, function() {
                       this.get_interface_object().prototype[member.name];
                   }.bind(this), "getting property on prototype object must throw TypeError");
                   // do_interface_attribute_asserts must be the last thing we
                   // do, since it will call done() on a_test.
                   this.do_interface_attribute_asserts(this.get_interface_object().prototype, member, a_test);
               } else {
                   promise_rejects_js(a_test, TypeError,
                                   this.get_interface_object().prototype[member.name])
                       .then(a_test.step_func(function() {
                           // do_interface_attribute_asserts must be the last
                           // thing we do, since it will call done() on a_test.
                           this.do_interface_attribute_asserts(this.get_interface_object().prototype,
                                                               member, a_test);
                       }.bind(this)));
               }
           } else {
               assert_equals(this.get_interface_object().prototype[member.name], undefined,
                             "getting property on prototype object must return undefined");
             // do_interface_attribute_asserts must be the last thing we do,
             // since it will call done() on a_test.
             this.do_interface_attribute_asserts(this.get_interface_object().prototype, member, a_test);
           }
       }
   }.bind(this));
};

IdlInterface.prototype.test_member_operation = function(member)
{
   if (!shouldRunSubTest(this.name)) {
       return;
   }
   var a_test = subsetTestByKey(this.name, async_test, this.name + " interface: operation " + member);
   a_test.step(function()
   {
       // This function tests WebIDL as of 2015-12-29.
       // https://webidl.spec.whatwg.org/#es-operations

       if (!this.should_have_interface_object()) {
           a_test.done();
           return;
       }

       this.assert_interface_object_exists();

       if (this.is_callback()) {
           assert_false("prototype" in this.get_interface_object(),
                        this.name + ' should not have a "prototype" property');
           a_test.done();
           return;
       }

       assert_own_property(this.get_interface_object(), "prototype",
                           'interface "' + this.name + '" does not have own property "prototype"');

       // "For each unique identifier of an exposed operation defined on the
       // interface, there must exist a corresponding property, unless the
       // effective overload set for that identifier and operation and with an
       // argument count of 0 has no entries."

       // TODO: Consider [Exposed].

       // "The location of the property is determined as follows:"
       var memberHolderObject;
       // "* If the operation is static, then the property exists on the
       //    interface object."
       if (member.special === "static") {
           assert_own_property(this.get_interface_object(), member.name,
                   "interface object missing static operation");
           memberHolderObject = this.get_interface_object();
       // "* Otherwise, [...] if the interface was declared with the [Global]
       //    extended attribute, then the property exists
       //    on every object that implements the interface."
       } else if (this.is_global()) {
           assert_own_property(self, member.name,
                   "global object missing non-static operation");
           memberHolderObject = self;
       // "* Otherwise, the property exists solely on the interface’s
       //    interface prototype object."
       } else {
           assert_own_property(this.get_interface_object().prototype, member.name,
                   "interface prototype object missing non-static operation");
           memberHolderObject = this.get_interface_object().prototype;
       }
       this.do_member_unscopable_asserts(member);
       this.do_member_operation_asserts(memberHolderObject, member, a_test);
   }.bind(this));
};

IdlInterface.prototype.do_member_unscopable_asserts = function(member)
{
   // Check that if the member is unscopable then it's in the
   // @@unscopables object properly.
   if (!member.isUnscopable) {
       return;
   }

   var unscopables = this.get_interface_object().prototype[Symbol.unscopables];
   var prop = member.name;
   var propDesc = Object.getOwnPropertyDescriptor(unscopables, prop);
   assert_equals(typeof propDesc, "object",
                 this.name + '.prototype[Symbol.unscopables].' + prop + ' must exist')
   assert_false("get" in propDesc,
                this.name + '.prototype[Symbol.unscopables].' + prop + ' must have no getter');
   assert_false("set" in propDesc,
                this.name + '.prototype[Symbol.unscopables].' + prop + ' must have no setter');
   assert_true(propDesc.writable,
               this.name + '.prototype[Symbol.unscopables].' + prop + ' must be writable');
   assert_true(propDesc.enumerable,
               this.name + '.prototype[Symbol.unscopables].' + prop + ' must be enumerable');
   assert_true(propDesc.configurable,
               this.name + '.prototype[Symbol.unscopables].' + prop + ' must be configurable');
   assert_equals(propDesc.value, true,
                 this.name + '.prototype[Symbol.unscopables].' + prop + ' must have the value `true`');
};

IdlInterface.prototype.do_member_operation_asserts = function(memberHolderObject, member, a_test)
{
   var done = a_test.done.bind(a_test);
   var operationUnforgeable = member.isUnforgeable;
   var desc = Object.getOwnPropertyDescriptor(memberHolderObject, member.name);
   // "The property has attributes { [[Writable]]: B,
   // [[Enumerable]]: true, [[Configurable]]: B }, where B is false if the
   // operation is unforgeable on the interface, and true otherwise".
   assert_false("get" in desc, "property should not have a getter");
   assert_false("set" in desc, "property should not have a setter");
   assert_equals(desc.writable, !operationUnforgeable,
                 "property should be writable if and only if not unforgeable");
   assert_true(desc.enumerable, "property should be enumerable");
   assert_equals(desc.configurable, !operationUnforgeable,
                 "property should be configurable if and only if not unforgeable");
   // "The value of the property is a Function object whose
   // behavior is as follows . . ."
   assert_equals(typeof memberHolderObject[member.name], "function",
                 "property must be a function");

   const operationOverloads = this.members.filter(function(m) {
       return m.type == "operation" && m.name == member.name &&
           (m.special === "static") === (member.special === "static");
   });
   assert_equals(
       memberHolderObject[member.name].length,
       minOverloadLength(operationOverloads),
       "property has wrong .length");
   assert_equals(
       memberHolderObject[member.name].name,
       member.name,
       "property has wrong .name");

   // Make some suitable arguments
   var args = member.arguments.map(function(arg) {
       return create_suitable_object(arg.idlType);
   });

   // "Let O be a value determined as follows:
   // ". . .
   // "Otherwise, throw a TypeError."
   // This should be hit if the operation is not static, there is
   // no [ImplicitThis] attribute, and the this value is null.
   //
   // TODO: We currently ignore the [ImplicitThis] case.  Except we manually
   // check for globals, since otherwise we'll invoke window.close().  And we
   // have to skip this test for anything that on the proto chain of "self",
   // since that does in fact have implicit-this behavior.
   if (member.special !== "static") {
       var cb;
       if (!this.is_global() &&
           memberHolderObject[member.name] != self[member.name])
       {
           cb = awaitNCallbacks(2, done);
           throwOrReject(a_test, member, memberHolderObject[member.name], null, args,
                         "calling operation with this = null didn't throw TypeError", cb);
       } else {
           cb = awaitNCallbacks(1, done);
       }

       // ". . . If O is not null and is also not a platform object
       // that implements interface I, throw a TypeError."
       //
       // TODO: Test a platform object that implements some other
       // interface.  (Have to be sure to get inheritance right.)
       throwOrReject(a_test, member, memberHolderObject[member.name], {}, args,
                     "calling operation with this = {} didn't throw TypeError", cb);
   } else {
       done();
   }
}

IdlInterface.prototype.test_to_json_operation = function(desc, memberHolderObject, member) {
   var instanceName = memberHolderObject && memberHolderObject.constructor.name
       || member.name + " object";
   if (member.has_extended_attribute("Default")) {
       subsetTestByKey(this.name, test, function() {
           var map = this.default_to_json_operation();
           var json = memberHolderObject.toJSON();
           map.forEach(function(type, k) {
               assert_true(k in json, "property " + JSON.stringify(k) + " should be present in the output of " + this.name + ".prototype.toJSON()");
               var descriptor = Object.getOwnPropertyDescriptor(json, k);
               assert_true(descriptor.writable, "property " + k + " should be writable");
               assert_true(descriptor.configurable, "property " + k + " should be configurable");
               assert_true(descriptor.enumerable, "property " + k + " should be enumerable");
               this.array.assert_type_is(json[k], type);
               delete json[k];
           }, this);
       }.bind(this), this.name + " interface: default toJSON operation on " + desc);
   } else {
       subsetTestByKey(this.name, test, function() {
           assert_true(this.array.is_json_type(member.idlType), JSON.stringify(member.idlType) + " is not an appropriate return value for the toJSON operation of " + instanceName);
           this.array.assert_type_is(memberHolderObject.toJSON(), member.idlType);
       }.bind(this), this.name + " interface: toJSON operation on " + desc);
   }
};

IdlInterface.prototype.test_member_maplike = function(member) {
   subsetTestByKey(this.name, test, () => {
       const proto = this.get_interface_object().prototype;

       const methods = [
           ["entries", 0],
           ["keys", 0],
           ["values", 0],
           ["forEach", 1],
           ["get", 1],
           ["has", 1]
       ];
       if (!member.readonly) {
           methods.push(
               ["set", 2],
               ["delete", 1],
               ["clear", 0]
           );
       }

       for (const [name, length] of methods) {
           const desc = Object.getOwnPropertyDescriptor(proto, name);
           assert_equals(typeof desc.value, "function", `${name} should be a function`);
           assert_equals(desc.enumerable, true, `${name} enumerable`);
           assert_equals(desc.configurable, true, `${name} configurable`);
           assert_equals(desc.writable, true, `${name} writable`);
           assert_equals(desc.value.length, length, `${name} function object length should be ${length}`);
           assert_equals(desc.value.name, name, `${name} function object should have the right name`);
       }

       const iteratorDesc = Object.getOwnPropertyDescriptor(proto, Symbol.iterator);
       assert_equals(iteratorDesc.value, proto.entries, `@@iterator should equal entries`);
       assert_equals(iteratorDesc.enumerable, false, `@@iterator enumerable`);
       assert_equals(iteratorDesc.configurable, true, `@@iterator configurable`);
       assert_equals(iteratorDesc.writable, true, `@@iterator writable`);

       const sizeDesc = Object.getOwnPropertyDescriptor(proto, "size");
       assert_equals(typeof sizeDesc.get, "function", `size getter should be a function`);
       assert_equals(sizeDesc.set, undefined, `size should not have a setter`);
       assert_equals(sizeDesc.enumerable, true, `size enumerable`);
       assert_equals(sizeDesc.configurable, true, `size configurable`);
       assert_equals(sizeDesc.get.length, 0, `size getter length`);
       assert_equals(sizeDesc.get.name, "get size", `size getter name`);
   }, `${this.name} interface: maplike<${member.idlType.map(t => t.idlType).join(", ")}>`);
};

IdlInterface.prototype.test_member_setlike = function(member) {
   subsetTestByKey(this.name, test, () => {
       const proto = this.get_interface_object().prototype;

       const methods = [
           ["entries", 0],
           ["keys", 0],
           ["values", 0],
           ["forEach", 1],
           ["has", 1]
       ];
       if (!member.readonly) {
           methods.push(
               ["add", 1],
               ["delete", 1],
               ["clear", 0]
           );
       }

       for (const [name, length] of methods) {
           const desc = Object.getOwnPropertyDescriptor(proto, name);
           assert_equals(typeof desc.value, "function", `${name} should be a function`);
           assert_equals(desc.enumerable, true, `${name} enumerable`);
           assert_equals(desc.configurable, true, `${name} configurable`);
           assert_equals(desc.writable, true, `${name} writable`);
           assert_equals(desc.value.length, length, `${name} function object length should be ${length}`);
           assert_equals(desc.value.name, name, `${name} function object should have the right name`);
       }

       const iteratorDesc = Object.getOwnPropertyDescriptor(proto, Symbol.iterator);
       assert_equals(iteratorDesc.value, proto.values, `@@iterator should equal values`);
       assert_equals(iteratorDesc.enumerable, false, `@@iterator enumerable`);
       assert_equals(iteratorDesc.configurable, true, `@@iterator configurable`);
       assert_equals(iteratorDesc.writable, true, `@@iterator writable`);

       const sizeDesc = Object.getOwnPropertyDescriptor(proto, "size");
       assert_equals(typeof sizeDesc.get, "function", `size getter should be a function`);
       assert_equals(sizeDesc.set, undefined, `size should not have a setter`);
       assert_equals(sizeDesc.enumerable, true, `size enumerable`);
       assert_equals(sizeDesc.configurable, true, `size configurable`);
       assert_equals(sizeDesc.get.length, 0, `size getter length`);
       assert_equals(sizeDesc.get.name, "get size", `size getter name`);
   }, `${this.name} interface: setlike<${member.idlType.map(t => t.idlType).join(", ")}>`);
};

IdlInterface.prototype.test_member_iterable = function(member) {
   subsetTestByKey(this.name, test, () => {
       const isPairIterator = member.idlType.length === 2;
       const proto = this.get_interface_object().prototype;

       const methods = [
           ["entries", 0],
           ["keys", 0],
           ["values", 0],
           ["forEach", 1]
       ];

       for (const [name, length] of methods) {
           const desc = Object.getOwnPropertyDescriptor(proto, name);
           assert_equals(typeof desc.value, "function", `${name} should be a function`);
           assert_equals(desc.enumerable, true, `${name} enumerable`);
           assert_equals(desc.configurable, true, `${name} configurable`);
           assert_equals(desc.writable, true, `${name} writable`);
           assert_equals(desc.value.length, length, `${name} function object length should be ${length}`);
           assert_equals(desc.value.name, name, `${name} function object should have the right name`);

           if (!isPairIterator) {
               assert_equals(desc.value, Array.prototype[name], `${name} equality with Array.prototype version`);
           }
       }

       const iteratorDesc = Object.getOwnPropertyDescriptor(proto, Symbol.iterator);
       assert_equals(iteratorDesc.enumerable, false, `@@iterator enumerable`);
       assert_equals(iteratorDesc.configurable, true, `@@iterator configurable`);
       assert_equals(iteratorDesc.writable, true, `@@iterator writable`);

       if (isPairIterator) {
           assert_equals(iteratorDesc.value, proto.entries, `@@iterator equality with entries`);
       } else {
           assert_equals(iteratorDesc.value, Array.prototype[Symbol.iterator], `@@iterator equality with Array.prototype version`);
       }
   }, `${this.name} interface: iterable<${member.idlType.map(t => t.idlType).join(", ")}>`);
};

IdlInterface.prototype.test_member_async_iterable = function(member) {
   subsetTestByKey(this.name, test, () => {
       const isPairIterator = member.idlType.length === 2;
       const proto = this.get_interface_object().prototype;

       // Note that although the spec allows arguments, which will be passed to the @@asyncIterator
       // method (which is either values or entries), those arguments must always be optional. So
       // length of 0 is still correct for values and entries.
       const methods = [
           ["values", 0],
       ];

       if (isPairIterator) {
           methods.push(
               ["entries", 0],
               ["keys", 0]
           );
       }

       for (const [name, length] of methods) {
           const desc = Object.getOwnPropertyDescriptor(proto, name);
           assert_equals(typeof desc.value, "function", `${name} should be a function`);
           assert_equals(desc.enumerable, true, `${name} enumerable`);
           assert_equals(desc.configurable, true, `${name} configurable`);
           assert_equals(desc.writable, true, `${name} writable`);
           assert_equals(desc.value.length, length, `${name} function object length should be ${length}`);
           assert_equals(desc.value.name, name, `${name} function object should have the right name`);
       }

       const iteratorDesc = Object.getOwnPropertyDescriptor(proto, Symbol.asyncIterator);
       assert_equals(iteratorDesc.enumerable, false, `@@iterator enumerable`);
       assert_equals(iteratorDesc.configurable, true, `@@iterator configurable`);
       assert_equals(iteratorDesc.writable, true, `@@iterator writable`);

       if (isPairIterator) {
           assert_equals(iteratorDesc.value, proto.entries, `@@iterator equality with entries`);
       } else {
           assert_equals(iteratorDesc.value, proto.values, `@@iterator equality with values`);
       }
   }, `${this.name} interface: async iterable<${member.idlType.map(t => t.idlType).join(", ")}>`);
};

IdlInterface.prototype.test_member_stringifier = function(member)
{
   subsetTestByKey(this.name, test, function()
   {
       if (!this.should_have_interface_object()) {
           return;
       }

       this.assert_interface_object_exists();

       if (this.is_callback()) {
           assert_false("prototype" in this.get_interface_object(),
                        this.name + ' should not have a "prototype" property');
           return;
       }

       assert_own_property(this.get_interface_object(), "prototype",
                           'interface "' + this.name + '" does not have own property "prototype"');

       // ". . . the property exists on the interface prototype object."
       var interfacePrototypeObject = this.get_interface_object().prototype;
       assert_own_property(interfacePrototypeObject, "toString",
               "interface prototype object missing non-static operation");

       var stringifierUnforgeable = member.isUnforgeable;
       var desc = Object.getOwnPropertyDescriptor(interfacePrototypeObject, "toString");
       // "The property has attributes { [[Writable]]: B,
       // [[Enumerable]]: true, [[Configurable]]: B }, where B is false if the
       // stringifier is unforgeable on the interface, and true otherwise."
       assert_false("get" in desc, "property should not have a getter");
       assert_false("set" in desc, "property should not have a setter");
       assert_equals(desc.writable, !stringifierUnforgeable,
                     "property should be writable if and only if not unforgeable");
       assert_true(desc.enumerable, "property should be enumerable");
       assert_equals(desc.configurable, !stringifierUnforgeable,
                     "property should be configurable if and only if not unforgeable");
       // "The value of the property is a Function object, which behaves as
       // follows . . ."
       assert_equals(typeof interfacePrototypeObject.toString, "function",
                     "property must be a function");
       // "The value of the Function object’s “length” property is the Number
       // value 0."
       assert_equals(interfacePrototypeObject.toString.length, 0,
           "property has wrong .length");

       // "Let O be the result of calling ToObject on the this value."
       assert_throws_js(globalOf(interfacePrototypeObject.toString).TypeError, function() {
           interfacePrototypeObject.toString.apply(null, []);
       }, "calling stringifier with this = null didn't throw TypeError");

       // "If O is not an object that implements the interface on which the
       // stringifier was declared, then throw a TypeError."
       //
       // TODO: Test a platform object that implements some other
       // interface.  (Have to be sure to get inheritance right.)
       assert_throws_js(globalOf(interfacePrototypeObject.toString).TypeError, function() {
           interfacePrototypeObject.toString.apply({}, []);
       }, "calling stringifier with this = {} didn't throw TypeError");
   }.bind(this), this.name + " interface: stringifier");
};

IdlInterface.prototype.test_members = function()
{
   var unexposed_members = new Set();
   for (var i = 0; i < this.members.length; i++)
   {
       var member = this.members[i];
       if (member.untested) {
           continue;
       }

       if (!exposed_in(exposure_set(member, this.exposureSet))) {
           if (!unexposed_members.has(member.name)) {
               unexposed_members.add(member.name);
               subsetTestByKey(this.name, test, function() {
                   // It's not exposed, so we shouldn't find it anywhere.
                   assert_false(member.name in this.get_interface_object(),
                               "The interface object must not have a property " +
                               format_value(member.name));
                   assert_false(member.name in this.get_interface_object().prototype,
                               "The prototype object must not have a property " +
                               format_value(member.name));
               }.bind(this), this.name + " interface: member " + member.name);
           }
           continue;
       }

       switch (member.type) {
       case "const":
           this.test_member_const(member);
           break;

       case "attribute":
           // For unforgeable attributes, we do the checks in
           // test_interface_of instead.
           if (!member.isUnforgeable)
           {
               this.test_member_attribute(member);
           }
           if (member.special === "stringifier") {
               this.test_member_stringifier(member);
           }
           break;

       case "operation":
           // TODO: Need to correctly handle multiple operations with the same
           // identifier.
           // For unforgeable operations, we do the checks in
           // test_interface_of instead.
           if (member.name) {
               if (!member.isUnforgeable)
               {
                   this.test_member_operation(member);
               }
           } else if (member.special === "stringifier") {
               this.test_member_stringifier(member);
           }
           break;

       case "iterable":
           if (member.async) {
               this.test_member_async_iterable(member);
           } else {
               this.test_member_iterable(member);
           }
           break;
       case "maplike":
           this.test_member_maplike(member);
           break;
       case "setlike":
           this.test_member_setlike(member);
           break;
       default:
           // TODO: check more member types.
           break;
       }
   }
};

IdlInterface.prototype.test_object = function(desc)
{
   var obj, exception = null;
   try
   {
       obj = eval(desc);
   }
   catch(e)
   {
       exception = e;
   }

   var expected_typeof;
   if (this.name == "HTMLAllCollection")
   {
       // Result of [[IsHTMLDDA]] slot
       expected_typeof = "undefined";
   }
   else
   {
       expected_typeof = "object";
   }

   if (this.is_callback()) {
       assert_equals(exception, null, "Unexpected exception when evaluating object");
       assert_equals(typeof obj, expected_typeof, "wrong typeof object");
   } else {
       this.test_primary_interface_of(desc, obj, exception, expected_typeof);

       var current_interface = this;
       while (current_interface)
       {
           if (!(current_interface.name in this.array.members))
           {
               throw new IdlHarnessError("Interface " + current_interface.name + " not found (inherited by " + this.name + ")");
           }
           if (current_interface.prevent_multiple_testing && current_interface.already_tested)
           {
               return;
           }
           current_interface.test_interface_of(desc, obj, exception, expected_typeof);
           current_interface = this.array.members[current_interface.base];
       }
   }
};

IdlInterface.prototype.test_primary_interface_of = function(desc, obj, exception, expected_typeof)
{
   // Only the object itself, not its members, are tested here, so if the
   // interface is untested, there is nothing to do.
   if (this.untested)
   {
       return;
   }

   // "The internal [[SetPrototypeOf]] method of every platform object that
   // implements an interface with the [Global] extended
   // attribute must execute the same algorithm as is defined for the
   // [[SetPrototypeOf]] internal method of an immutable prototype exotic
   // object."
   // https://webidl.spec.whatwg.org/#platform-object-setprototypeof
   if (this.is_global())
   {
       this.test_immutable_prototype("global platform object", obj);
   }


   // We can't easily test that its prototype is correct if there's no
   // interface object, or the object is from a different global environment
   // (not instanceof Object).  TODO: test in this case that its prototype at
   // least looks correct, even if we can't test that it's actually correct.
   if (this.should_have_interface_object()
   && (typeof obj != expected_typeof || obj instanceof Object))
   {
       subsetTestByKey(this.name, test, function()
       {
           assert_equals(exception, null, "Unexpected exception when evaluating object");
           assert_equals(typeof obj, expected_typeof, "wrong typeof object");
           this.assert_interface_object_exists();
           assert_own_property(this.get_interface_object(), "prototype",
                               'interface "' + this.name + '" does not have own property "prototype"');

           // "The value of the internal [[Prototype]] property of the
           // platform object is the interface prototype object of the primary
           // interface from the platform object’s associated global
           // environment."
           assert_equals(Object.getPrototypeOf(obj),
                         this.get_interface_object().prototype,
                         desc + "'s prototype is not " + this.name + ".prototype");
       }.bind(this), this.name + " must be primary interface of " + desc);
   }

   // "The class string of a platform object that implements one or more
   // interfaces must be the qualified name of the primary interface of the
   // platform object."
   subsetTestByKey(this.name, test, function()
   {
       assert_equals(exception, null, "Unexpected exception when evaluating object");
       assert_equals(typeof obj, expected_typeof, "wrong typeof object");
       assert_class_string(obj, this.get_qualified_name(), "class string of " + desc);
       if (!this.has_stringifier())
       {
           assert_equals(String(obj), "[object " + this.get_qualified_name() + "]", "String(" + desc + ")");
       }
   }.bind(this), "Stringification of " + desc);
};

IdlInterface.prototype.test_interface_of = function(desc, obj, exception, expected_typeof)
{
   // TODO: Indexed and named properties, more checks on interface members
   this.already_tested = true;
   if (!shouldRunSubTest(this.name)) {
       return;
   }

   var unexposed_properties = new Set();
   for (var i = 0; i < this.members.length; i++)
   {
       var member = this.members[i];
       if (member.untested) {
           continue;
       }
       if (!exposed_in(exposure_set(member, this.exposureSet)))
       {
           if (!unexposed_properties.has(member.name))
           {
               unexposed_properties.add(member.name);
               subsetTestByKey(this.name, test, function() {
                   assert_equals(exception, null, "Unexpected exception when evaluating object");
                   assert_false(member.name in obj);
               }.bind(this), this.name + " interface: " + desc + ' must not have property "' + member.name + '"');
           }
           continue;
       }
       if (member.type == "attribute" && member.isUnforgeable)
       {
           var a_test = subsetTestByKey(this.name, async_test, this.name + " interface: " + desc + ' must have own property "' + member.name + '"');
           a_test.step(function() {
               assert_equals(exception, null, "Unexpected exception when evaluating object");
               assert_equals(typeof obj, expected_typeof, "wrong typeof object");
               // Call do_interface_attribute_asserts last, since it will call a_test.done()
               this.do_interface_attribute_asserts(obj, member, a_test);
           }.bind(this));
       }
       else if (member.type == "operation" &&
                member.name &&
                member.isUnforgeable)
       {
           var a_test = subsetTestByKey(this.name, async_test, this.name + " interface: " + desc + ' must have own property "' + member.name + '"');
           a_test.step(function()
           {
               assert_equals(exception, null, "Unexpected exception when evaluating object");
               assert_equals(typeof obj, expected_typeof, "wrong typeof object");
               assert_own_property(obj, member.name,
                                   "Doesn't have the unforgeable operation property");
               this.do_member_operation_asserts(obj, member, a_test);
           }.bind(this));
       }
       else if ((member.type == "const"
       || member.type == "attribute"
       || member.type == "operation")
       && member.name)
       {
           subsetTestByKey(this.name, test, function()
           {
               assert_equals(exception, null, "Unexpected exception when evaluating object");
               assert_equals(typeof obj, expected_typeof, "wrong typeof object");
               if (member.special !== "static") {
                   if (!this.is_global()) {
                       assert_inherits(obj, member.name);
                   } else {
                       assert_own_property(obj, member.name);
                   }

                   if (member.type == "const")
                   {
                       assert_equals(obj[member.name], constValue(member.value));
                   }
                   if (member.type == "attribute")
                   {
                       // Attributes are accessor properties, so they might
                       // legitimately throw an exception rather than returning
                       // anything.
                       var property, thrown = false;
                       try
                       {
                           property = obj[member.name];
                       }
                       catch (e)
                       {
                           thrown = true;
                       }
                       if (!thrown)
                       {
                           if (this.name == "Document" && member.name == "all")
                           {
                               // Result of [[IsHTMLDDA]] slot
                               assert_equals(typeof property, "undefined");
                           }
                           else
                           {
                               this.array.assert_type_is(property, member.idlType);
                           }
                       }
                   }
                   if (member.type == "operation")
                   {
                       assert_equals(typeof obj[member.name], "function");
                   }
               }
           }.bind(this), this.name + " interface: " + desc + ' must inherit property "' + member + '" with the proper type');
       }
       // TODO: This is wrong if there are multiple operations with the same
       // identifier.
       // TODO: Test passing arguments of the wrong type.
       if (member.type == "operation" && member.name && member.arguments.length)
       {
           var description =
               this.name + " interface: calling " + member + " on " + desc +
               " with too few arguments must throw TypeError";
           var a_test = subsetTestByKey(this.name, async_test, description);
           a_test.step(function()
           {
               assert_equals(exception, null, "Unexpected exception when evaluating object");
               assert_equals(typeof obj, expected_typeof, "wrong typeof object");
               var fn;
               if (member.special !== "static") {
                   if (!this.is_global() && !member.isUnforgeable) {
                       assert_inherits(obj, member.name);
                   } else {
                       assert_own_property(obj, member.name);
                   }
                   fn = obj[member.name];
               }
               else
               {
                   assert_own_property(obj.constructor, member.name, "interface object must have static operation as own property");
                   fn = obj.constructor[member.name];
               }

               var minLength = minOverloadLength(this.members.filter(function(m) {
                   return m.type == "operation" && m.name == member.name;
               }));
               var args = [];
               var cb = awaitNCallbacks(minLength, a_test.done.bind(a_test));
               for (var i = 0; i < minLength; i++) {
                   throwOrReject(a_test, member, fn, obj, args, "Called with " + i + " arguments", cb);

                   args.push(create_suitable_object(member.arguments[i].idlType));
               }
               if (minLength === 0) {
                   cb();
               }
           }.bind(this));
       }

       if (member.is_to_json_regular_operation()) {
           this.test_to_json_operation(desc, obj, member);
       }
   }
};

IdlInterface.prototype.has_stringifier = function()
{
   if (this.name === "DOMException") {
       // toString is inherited from Error, so don't assume we have the
       // default stringifer
       return true;
   }
   if (this.members.some(function(member) { return member.special === "stringifier"; })) {
       return true;
   }
   if (this.base &&
       this.array.members[this.base].has_stringifier()) {
       return true;
   }
   return false;
};

IdlInterface.prototype.do_interface_attribute_asserts = function(obj, member, a_test)
{
   // This function tests WebIDL as of 2015-01-27.
   // TODO: Consider [Exposed].

   // This is called by test_member_attribute() with the prototype as obj if
   // it is not a global, and the global otherwise, and by test_interface_of()
   // with the object as obj.

   var pendingPromises = [];

   // "The name of the property is the identifier of the attribute."
   assert_own_property(obj, member.name);

   // "The property has attributes { [[Get]]: G, [[Set]]: S, [[Enumerable]]:
   // true, [[Configurable]]: configurable }, where:
   // "configurable is false if the attribute was declared with the
   // [LegacyUnforgeable] extended attribute and true otherwise;
   // "G is the attribute getter, defined below; and
   // "S is the attribute setter, also defined below."
   var desc = Object.getOwnPropertyDescriptor(obj, member.name);
   assert_false("value" in desc, 'property descriptor should not have a "value" field');
   assert_false("writable" in desc, 'property descriptor should not have a "writable" field');
   assert_true(desc.enumerable, "property should be enumerable");
   if (member.isUnforgeable)
   {
       assert_false(desc.configurable, "[LegacyUnforgeable] property must not be configurable");
   }
   else
   {
       assert_true(desc.configurable, "property must be configurable");
   }


   // "The attribute getter is a Function object whose behavior when invoked
   // is as follows:"
   assert_equals(typeof desc.get, "function", "getter must be Function");

   // "If the attribute is a regular attribute, then:"
   if (member.special !== "static") {
       // "If O is not a platform object that implements I, then:
       // "If the attribute was specified with the [LegacyLenientThis] extended
       // attribute, then return undefined.
       // "Otherwise, throw a TypeError."
       if (!member.has_extended_attribute("LegacyLenientThis")) {
           if (member.idlType.generic !== "Promise") {
               assert_throws_js(globalOf(desc.get).TypeError, function() {
                   desc.get.call({});
               }.bind(this), "calling getter on wrong object type must throw TypeError");
           } else {
               pendingPromises.push(
                   promise_rejects_js(a_test, TypeError, desc.get.call({}),
                                   "calling getter on wrong object type must reject the return promise with TypeError"));
           }
       } else {
           assert_equals(desc.get.call({}), undefined,
                         "calling getter on wrong object type must return undefined");
       }
   }

   // "The value of the Function object’s “length” property is the Number
   // value 0."
   assert_equals(desc.get.length, 0, "getter length must be 0");

   // "Let name be the string "get " prepended to attribute’s identifier."
   // "Perform ! SetFunctionName(F, name)."
   assert_equals(desc.get.name, "get " + member.name,
       "getter must have the name 'get " + member.name + "'");


   // TODO: Test calling setter on the interface prototype (should throw
   // TypeError in most cases).
   if (member.readonly
   && !member.has_extended_attribute("LegacyLenientSetter")
   && !member.has_extended_attribute("PutForwards")
   && !member.has_extended_attribute("Replaceable"))
   {
       // "The attribute setter is undefined if the attribute is declared
       // readonly and has neither a [PutForwards] nor a [Replaceable]
       // extended attribute declared on it."
       assert_equals(desc.set, undefined, "setter must be undefined for readonly attributes");
   }
   else
   {
       // "Otherwise, it is a Function object whose behavior when
       // invoked is as follows:"
       assert_equals(typeof desc.set, "function", "setter must be function for PutForwards, Replaceable, or non-readonly attributes");

       // "If the attribute is a regular attribute, then:"
       if (member.special !== "static") {
           // "If /validThis/ is false and the attribute was not specified
           // with the [LegacyLenientThis] extended attribute, then throw a
           // TypeError."
           // "If the attribute is declared with a [Replaceable] extended
           // attribute, then: ..."
           // "If validThis is false, then return."
           if (!member.has_extended_attribute("LegacyLenientThis")) {
               assert_throws_js(globalOf(desc.set).TypeError, function() {
                   desc.set.call({});
               }.bind(this), "calling setter on wrong object type must throw TypeError");
           } else {
               assert_equals(desc.set.call({}), undefined,
                             "calling setter on wrong object type must return undefined");
           }
       }

       // "The value of the Function object’s “length” property is the Number
       // value 1."
       assert_equals(desc.set.length, 1, "setter length must be 1");

       // "Let name be the string "set " prepended to id."
       // "Perform ! SetFunctionName(F, name)."
       assert_equals(desc.set.name, "set " + member.name,
           "The attribute setter must have the name 'set " + member.name + "'");
   }

   Promise.all(pendingPromises).then(a_test.done.bind(a_test));
}

/// IdlInterfaceMember ///
function IdlInterfaceMember(obj)
{
   /**
    * obj is an object produced by the WebIDLParser.js "ifMember" production.
    * We just forward all properties to this object without modification,
    * except for special extAttrs handling.
    */
   for (var k in obj.toJSON())
   {
       this[k] = obj[k];
   }
   if (!("extAttrs" in this))
   {
       this.extAttrs = [];
   }

   this.isUnforgeable = this.has_extended_attribute("LegacyUnforgeable");
   this.isUnscopable = this.has_extended_attribute("Unscopable");
}

IdlInterfaceMember.prototype = Object.create(IdlObject.prototype);

IdlInterfaceMember.prototype.toJSON = function() {
   return this;
};

IdlInterfaceMember.prototype.is_to_json_regular_operation = function() {
   return this.type == "operation" && this.special !== "static" && this.name == "toJSON";
};

IdlInterfaceMember.prototype.toString = function() {
   function formatType(type) {
       var result;
       if (type.generic) {
           result = type.generic + "<" + type.idlType.map(formatType).join(", ") + ">";
       } else if (type.union) {
           result = "(" + type.subtype.map(formatType).join(" or ") + ")";
       } else {
           result = type.idlType;
       }
       if (type.nullable) {
           result += "?"
       }
       return result;
   }

   if (this.type === "operation") {
       var args = this.arguments.map(function(m) {
           return [
               m.optional ? "optional " : "",
               formatType(m.idlType),
               m.variadic ? "..." : "",
           ].join("");
       }).join(", ");
       return this.name + "(" + args + ")";
   }

   return this.name;
}

/// Internal helper functions ///
function create_suitable_object(type)
{
   /**
    * type is an object produced by the WebIDLParser.js "type" production.  We
    * return a JavaScript value that matches the type, if we can figure out
    * how.
    */
   if (type.nullable)
   {
       return null;
   }
   switch (type.idlType)
   {
       case "any":
       case "boolean":
           return true;

       case "byte": case "octet": case "short": case "unsigned short":
       case "long": case "unsigned long": case "long long":
       case "unsigned long long": case "float": case "double":
       case "unrestricted float": case "unrestricted double":
           return 7;

       case "DOMString":
       case "ByteString":
       case "USVString":
           return "foo";

       case "object":
           return {a: "b"};

       case "Node":
           return document.createTextNode("abc");
   }
   return null;
}

/// IdlEnum ///
// Used for IdlArray.prototype.assert_type_is
function IdlEnum(obj)
{
   /**
    * obj is an object produced by the WebIDLParser.js "dictionary"
    * production.
    */

   /** Self-explanatory. */
   this.name = obj.name;

   /** An array of values produced by the "enum" production. */
   this.values = obj.values;

}

IdlEnum.prototype = Object.create(IdlObject.prototype);

/// IdlCallback ///
// Used for IdlArray.prototype.assert_type_is
function IdlCallback(obj)
{
   /**
    * obj is an object produced by the WebIDLParser.js "callback"
    * production.
    */

   /** Self-explanatory. */
   this.name = obj.name;

   /** Arguments for the callback. */
   this.arguments = obj.arguments;
}

IdlCallback.prototype = Object.create(IdlObject.prototype);

/// IdlTypedef ///
// Used for IdlArray.prototype.assert_type_is
function IdlTypedef(obj)
{
   /**
    * obj is an object produced by the WebIDLParser.js "typedef"
    * production.
    */

   /** Self-explanatory. */
   this.name = obj.name;

   /** The idlType that we are supposed to be typedeffing to. */
   this.idlType = obj.idlType;

}

IdlTypedef.prototype = Object.create(IdlObject.prototype);

/// IdlNamespace ///
function IdlNamespace(obj)
{
   this.name = obj.name;
   this.extAttrs = obj.extAttrs;
   this.untested = obj.untested;
   /** A back-reference to our IdlArray. */
   this.array = obj.array;

   /** An array of IdlInterfaceMembers. */
   this.members = obj.members.map(m => new IdlInterfaceMember(m));
}

IdlNamespace.prototype = Object.create(IdlObject.prototype);

IdlNamespace.prototype.do_member_operation_asserts = function (memberHolderObject, member, a_test)
{
   var desc = Object.getOwnPropertyDescriptor(memberHolderObject, member.name);

   assert_false("get" in desc, "property should not have a getter");
   assert_false("set" in desc, "property should not have a setter");
   assert_equals(
       desc.writable,
       !member.isUnforgeable,
       "property should be writable if and only if not unforgeable");
   assert_true(desc.enumerable, "property should be enumerable");
   assert_equals(
       desc.configurable,
       !member.isUnforgeable,
       "property should be configurable if and only if not unforgeable");

   assert_equals(
       typeof memberHolderObject[member.name],
       "function",
        "property must be a function");

   assert_equals(
       memberHolderObject[member.name].length,
       minOverloadLength(this.members.filter(function(m) {
           return m.type == "operation" && m.name == member.name;
       })),
       "operation has wrong .length");
   a_test.done();
}

IdlNamespace.prototype.test_member_operation = function(member)
{
   if (!shouldRunSubTest(this.name)) {
       return;
   }
   var a_test = subsetTestByKey(
       this.name,
       async_test,
       this.name + ' namespace: operation ' + member);
   a_test.step(function() {
       assert_own_property(
           self[this.name],
           member.name,
           'namespace object missing operation ' + format_value(member.name));

       this.do_member_operation_asserts(self[this.name], member, a_test);
   }.bind(this));
};

IdlNamespace.prototype.test_member_attribute = function (member)
{
   if (!shouldRunSubTest(this.name)) {
       return;
   }
   var a_test = subsetTestByKey(
       this.name,
       async_test,
       this.name + ' namespace: attribute ' + member.name);
   a_test.step(function()
   {
       assert_own_property(
           self[this.name],
           member.name,
           this.name + ' does not have property ' + format_value(member.name));

       var desc = Object.getOwnPropertyDescriptor(self[this.name], member.name);
       assert_equals(desc.set, undefined, "setter must be undefined for namespace members");
       a_test.done();
   }.bind(this));
};

IdlNamespace.prototype.test_self = function ()
{
   /**
    * TODO(lukebjerring): Assert:
    * - "Note that unlike interfaces or dictionaries, namespaces do not create types."
    */

   subsetTestByKey(this.name, test, () => {
       assert_true(this.extAttrs.every(o => o.name === "Exposed" || o.name === "SecureContext"),
           "Only the [Exposed] and [SecureContext] extended attributes are applicable to namespaces");
       assert_true(this.has_extended_attribute("Exposed"),
           "Namespaces must be annotated with the [Exposed] extended attribute");
   }, `${this.name} namespace: extended attributes`);

   const namespaceObject = self[this.name];

   subsetTestByKey(this.name, test, () => {
       const desc = Object.getOwnPropertyDescriptor(self, this.name);
       assert_equals(desc.value, namespaceObject, `wrong value for ${this.name} namespace object`);
       assert_true(desc.writable, "namespace object should be writable");
       assert_false(desc.enumerable, "namespace object should not be enumerable");
       assert_true(desc.configurable, "namespace object should be configurable");
       assert_false("get" in desc, "namespace object should not have a getter");
       assert_false("set" in desc, "namespace object should not have a setter");
   }, `${this.name} namespace: property descriptor`);

   subsetTestByKey(this.name, test, () => {
       assert_true(Object.isExtensible(namespaceObject));
   }, `${this.name} namespace: [[Extensible]] is true`);

   subsetTestByKey(this.name, test, () => {
       assert_true(namespaceObject instanceof Object);

       if (this.name === "console") {
           // https://console.spec.whatwg.org/#console-namespace
           const namespacePrototype = Object.getPrototypeOf(namespaceObject);
           assert_equals(Reflect.ownKeys(namespacePrototype).length, 0);
           assert_equals(Object.getPrototypeOf(namespacePrototype), Object.prototype);
       } else {
           assert_equals(Object.getPrototypeOf(namespaceObject), Object.prototype);
       }
   }, `${this.name} namespace: [[Prototype]] is Object.prototype`);

   subsetTestByKey(this.name, test, () => {
       assert_equals(typeof namespaceObject, "object");
   }, `${this.name} namespace: typeof is "object"`);

   subsetTestByKey(this.name, test, () => {
       assert_equals(
           Object.getOwnPropertyDescriptor(namespaceObject, "length"),
           undefined,
           "length property must be undefined"
       );
   }, `${this.name} namespace: has no length property`);

   subsetTestByKey(this.name, test, () => {
       assert_equals(
           Object.getOwnPropertyDescriptor(namespaceObject, "name"),
           undefined,
           "name property must be undefined"
       );
   }, `${this.name} namespace: has no name property`);
};

IdlNamespace.prototype.test = function ()
{
   // If the namespace object is not exposed, only test that. Members can't be
   // tested either
   if (!this.exposed) {
       if (!this.untested) {
           subsetTestByKey(this.name, test, function() {
               assert_false(this.name in self, this.name + " namespace should not exist");
           }.bind(this), this.name + " namespace: existence and properties of namespace object");
       }
       return;
   }

   if (!this.untested) {
       this.test_self();
   }

   for (const v of Object.values(this.members)) {
       switch (v.type) {

       case 'operation':
           this.test_member_operation(v);
           break;

       case 'attribute':
           this.test_member_attribute(v);
           break;

       default:
           throw 'Invalid namespace member ' + v.name + ': ' + v.type + ' not supported';
       }
   };
};

}());

/**
* idl_test is a promise_test wrapper that handles the fetching of the IDL,
* avoiding repetitive boilerplate.
*
* @param {String[]} srcs Spec name(s) for source idl files (fetched from
*      /interfaces/{name}.idl).
* @param {String[]} deps Spec name(s) for dependency idl files (fetched
*      from /interfaces/{name}.idl). Order is important - dependencies from
*      each source will only be included if they're already know to be a
*      dependency (i.e. have already been seen).
* @param {Function} setup_func Function for extra setup of the idl_array, such
*      as adding objects. Do not call idl_array.test() in the setup; it is
*      called by this function (idl_test).
*/
function idl_test(srcs, deps, idl_setup_func) {
   return promise_test(function (t) {
       var idl_array = new IdlArray();
       var setup_error = null;
       const validationIgnored = [
           "constructor-member",
           "dict-arg-default",
           "require-exposed"
       ];
       return Promise.all(
           srcs.concat(deps).map(globalThis.fetch_spec))
           .then(function(results) {
               const astArray = results.map(result =>
                   WebIDL2.parse(result.idl, { sourceName: result.spec })
               );
               test(() => {
                   const validations = WebIDL2.validate(astArray)
                       .filter(v => !validationIgnored.includes(v.ruleName));
                   if (validations.length) {
                       const message = validations.map(v => v.message).join("\n\n");
                       throw new Error(message);
                   }
               }, "idl_test validation");
               for (var i = 0; i < srcs.length; i++) {
                   idl_array.internal_add_idls(astArray[i]);
               }
               for (var i = srcs.length; i < srcs.length + deps.length; i++) {
                   idl_array.internal_add_dependency_idls(astArray[i]);
               }
           })
           .then(function() {
               if (idl_setup_func) {
                   return idl_setup_func(idl_array, t);
               }
           })
           .catch(function(e) { setup_error = e || 'IDL setup failed.'; })
           .then(function () {
               var error = setup_error;
               try {
                   idl_array.test(); // Test what we can.
               } catch (e) {
                   // If testing fails hard here, the original setup error
                   // is more likely to be the real cause.
                   error = error || e;
               }
               if (error) {
                   throw error;
               }
           });
   }, 'idl_test setup');
}
globalThis.idl_test = idl_test;

/**
* fetch_spec is a shorthand for a Promise that fetches the spec's content.
* Note: ShadowRealm-specific implementation in testharness-shadowrealm-inner.js
*/
function fetch_spec(spec) {
   var url = '/interfaces/' + spec + '.idl';
   return fetch(url).then(function (r) {
       if (!r.ok) {
           throw new IdlHarnessError("Error fetching " + url + ".");
       }
       return r.text();
   }).then(idl => ({ spec, idl }));
}
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