webidl2/lib/webidl2.js

"use strict";

(() => {
  // These regular expressions use the sticky flag so they will only match at
  // the current location (ie. the offset of lastIndex).
  const tokenRe = {
    // This expression uses a lookahead assertion to catch false matches
    // against integers early.
    "float": /-?(?=[0-9]*\.|[0-9]+[eE])(([0-9]+\.[0-9]*|[0-9]*\.[0-9]+)([Ee][-+]?[0-9]+)?|[0-9]+[Ee][-+]?[0-9]+)/y,
    "integer": /-?(0([Xx][0-9A-Fa-f]+|[0-7]*)|[1-9][0-9]*)/y,
    "identifier": /_?[A-Za-z][0-9A-Z_a-z-]*/y,
    "string": /"[^"]*"/y,
    "whitespace": /[\t\n\r ]+/y,
    "comment": /((\/(\/.*|\*([^*]|\*[^\/])*\*\/)[\t\n\r ]*)+)/y,
    "other": /[^\t\n\r 0-9A-Za-z]/y
  };

  const stringTypes = [
    "ByteString",
    "DOMString",
    "USVString"
  ];

  const argumentNameKeywords = [
    "attribute",
    "callback",
    "const",
    "deleter",
    "dictionary",
    "enum",
    "getter",
    "includes",
    "inherit",
    "interface",
    "iterable",
    "maplike",
    "namespace",
    "partial",
    "required",
    "setlike",
    "setter",
    "static",
    "stringifier",
    "typedef",
    "unrestricted"
  ];

  const nonRegexTerminals = [
    "FrozenArray",
    "Infinity",
    "NaN",
    "Promise",
    "boolean",
    "byte",
    "double",
    "false",
    "float",
    "implements",
    "legacyiterable",
    "long",
    "mixin",
    "null",
    "octet",
    "optional",
    "or",
    "readonly",
    "record",
    "sequence",
    "short",
    "true",
    "unsigned",
    "void"
  ].concat(argumentNameKeywords, stringTypes);

  const punctuations = [
    "(",
    ")",
    ",",
    "-Infinity",
    "...",
    ":",
    ";",
    "<",
    "=",
    ">",
    "?",
    "[",
    "]",
    "{",
    "}"
  ];

  function tokenise(str) {
    const tokens = [];
    let lastIndex = 0;
    let trivia = "";
    while (lastIndex < str.length) {
      const nextChar = str.charAt(lastIndex);
      let result = -1;

      if (/[\t\n\r ]/.test(nextChar)) {
        result = attemptTokenMatch("whitespace", { noFlushTrivia: true });
      } else if (nextChar === '/') {
        result = attemptTokenMatch("comment", { noFlushTrivia: true });
      }

      if (result !== -1) {
        trivia += tokens.pop().value;
      } else if (/[-0-9.]/.test(nextChar)) {
        result = attemptTokenMatch("float");
        if (result === -1) {
          result = attemptTokenMatch("integer");
        }
      } else if (/[A-Z_a-z]/.test(nextChar)) {
        result = attemptTokenMatch("identifier");
        const token = tokens[tokens.length - 1];
        if (result !== -1 && nonRegexTerminals.includes(token.value)) {
          token.type = token.value;
        }
      } else if (nextChar === '"') {
        result = attemptTokenMatch("string");
      }

      for (const punctuation of punctuations) {
        if (str.startsWith(punctuation, lastIndex)) {
          tokens.push({ type: punctuation, value: punctuation, trivia });
          trivia = "";
          lastIndex += punctuation.length;
          result = lastIndex;
          break;
        }
      }

      // other as the last try
      if (result === -1) {
        result = attemptTokenMatch("other");
      }
      if (result === -1) {
        throw new Error("Token stream not progressing");
      }
      lastIndex = result;
    }
    return tokens;

    function attemptTokenMatch(type, { noFlushTrivia } = {}) {
      const re = tokenRe[type];
      re.lastIndex = lastIndex;
      const result = re.exec(str);
      if (result) {
        tokens.push({ type, value: result[0], trivia });
        if (!noFlushTrivia) {
          trivia = "";
        }
        return re.lastIndex;
      }
      return -1;
    }
  }

  class WebIDLParseError {
    constructor(str, line, input, tokens) {
      this.message = str;
      this.line = line;
      this.input = input;
      this.tokens = tokens;
    }

    toString() {
      const escapedInput = JSON.stringify(this.input);
      const tokens = JSON.stringify(this.tokens, null, 4);
      return `${this.message}, line ${this.line} (tokens: ${escapedInput})\n${tokens}`;
    }
  }

  function parse(tokens) {
    let line = 1;
    tokens = tokens.slice();
    const names = new Map();
    let current = null;

    const FLOAT = "float";
    const INT = "integer";
    const ID = "identifier";
    const STR = "string";
    const OTHER = "other";

    const EMPTY_OPERATION = Object.freeze({
      type: "operation",
      getter: false,
      setter: false,
      deleter: false,
      static: false,
      stringifier: false
    });

    const EMPTY_IDLTYPE = Object.freeze({
      generic: null,
      nullable: false,
      union: false,
      idlType: null,
      extAttrs: []
    });

    function error(str) {
      const maxTokens = 5;
      const tok = tokens
        .slice(consume_position, consume_position + maxTokens)
        .map(t => t.trivia + t.value).join("");
      // Count newlines preceding the actual erroneous token
      if (tokens.length) {
        line += count(tokens[consume_position].trivia, "\n");
      }

      let message;
      if (current) {
        message = `Got an error during or right after parsing \`${current.partial ? "partial " : ""}${current.type} ${current.name}\`: ${str}`
      }
      else {
        // throwing before any valid definition
        message = `Got an error before parsing any named definition: ${str}`;
      }

      throw new WebIDLParseError(message, line, tok, tokens.slice(0, maxTokens));
    }

    function sanitize_name(name, type) {
      if (names.has(name)) {
        error(`The name "${name}" of type "${names.get(name)}" is already seen`);
      }
      names.set(name, type);
      return name;
    }

    let consume_position = 0;

    function probe(type) {
      return tokens.length > consume_position && tokens[consume_position].type === type;
    }

    function consume(...candidates) {
      // TODO: use const when Servo updates its JS engine
      for (let type of candidates) {
        if (!probe(type)) continue;
        const token = tokens[consume_position];
        consume_position++;
        line += count(token.trivia, "\n");
        return token;
      }
    }

    function unescape(identifier) {
      return identifier.startsWith('_') ? identifier.slice(1) : identifier;
    }

    function unconsume(position) {
      while (consume_position > position) {
        consume_position--;
        line -= count(tokens[consume_position].trivia, "\n");
      }
    }

    function count(str, char) {
      let total = 0;
      for (let i = str.indexOf(char); i !== -1; i = str.indexOf(char, i + 1)) {
        ++total;
      }
      return total;
    }

    function integer_type() {
      let ret = "";
      if (consume("unsigned")) ret = "unsigned ";
      if (consume("short")) return ret + "short";
      if (consume("long")) {
        ret += "long";
        if (consume("long")) return ret + " long";
        return ret;
      }
      if (ret) error("Failed to parse integer type");
    }

    function float_type() {
      let ret = "";
      if (consume("unrestricted")) ret = "unrestricted ";
      if (consume("float")) return ret + "float";
      if (consume("double")) return ret + "double";
      if (ret) error("Failed to parse float type");
    }

    function primitive_type() {
      const num_type = integer_type() || float_type();
      if (num_type) return num_type;
      if (consume("boolean")) return "boolean";
      if (consume("byte")) return "byte";
      if (consume("octet")) return "octet";
    }

    function const_value() {
      if (consume("true")) return { type: "boolean", value: true };
      if (consume("false")) return { type: "boolean", value: false };
      if (consume("null")) return { type: "null" };
      if (consume("Infinity")) return { type: "Infinity", negative: false };
      if (consume("-Infinity")) return { type: "Infinity", negative: true };
      if (consume("NaN")) return { type: "NaN" };
      const ret = consume(FLOAT, INT);
      if (ret) return { type: "number", value: ret.value };
    }

    function type_suffix(obj) {
      obj.nullable = !!consume("?");
      if (probe("?")) error("Can't nullable more than once");
    }

    function generic_type(typeName) {
      const name = consume("FrozenArray", "Promise", "sequence", "record");
      if (!name) {
        return;
      }
      const ret = { generic: name.type };
      consume("<") || error(`No opening bracket after ${name.type}`);
      switch (name.type) {
        case "Promise":
          if (probe("[")) error("Promise type cannot have extended attribute");
          ret.idlType = return_type(typeName);
          break;
        case "sequence":
        case "FrozenArray":
          ret.idlType = type_with_extended_attributes(typeName);
          break;
        case "record":
          if (probe("[")) error("Record key cannot have extended attribute");
          ret.idlType = [];
          const keyType = consume(...stringTypes);
          if (!keyType) error(`Record key must be a string type`);
          ret.idlType.push(Object.assign({ type: typeName }, EMPTY_IDLTYPE, { idlType: keyType.value }));
          consume(",") || error("Missing comma after record key type");
          const valueType = type_with_extended_attributes(typeName) || error("Error parsing generic type record");
          ret.idlType.push(valueType);
          break;
      }
      if (!ret.idlType) error(`Error parsing generic type ${name.type}`);
      consume(">") || error(`Missing closing bracket after ${name.type}`);
      if (name.type === "Promise" && probe("?")) {
        error("Promise type cannot be nullable");
      }
      type_suffix(ret);
      return ret;
    }

    function single_type(typeName) {
      const ret = Object.assign({ type: typeName || null }, EMPTY_IDLTYPE);
      const generic = generic_type(typeName);
      if (generic) {
        return Object.assign(ret, generic);
      }
      const prim = primitive_type();
      let name;
      if (prim) {
        ret.idlType = prim;
      } else if (name = consume(ID, ...stringTypes)) {
        ret.idlType = name.value;
        if (probe("<")) error(`Unsupported generic type ${name.value}`);
      } else {
        return;
      }
      type_suffix(ret);
      if (ret.nullable && ret.idlType === "any") error("Type any cannot be made nullable");
      return ret;
    }

    function union_type(typeName) {
      if (!consume("(")) return;
      const ret = Object.assign({ type: typeName || null }, EMPTY_IDLTYPE, { union: true, idlType: [] });
      do {
        const typ = type_with_extended_attributes() || error("No type after open parenthesis or 'or' in union type");
        ret.idlType.push(typ);
      } while (consume("or"));
      if (ret.idlType.length < 2) {
        error("At least two types are expected in a union type but found less");
      }
      if (!consume(")")) error("Unterminated union type");
      type_suffix(ret);
      return ret;
    }

    function type(typeName) {
      return single_type(typeName) || union_type(typeName);
    }

    function type_with_extended_attributes(typeName) {
      const extAttrs = extended_attrs();
      const ret = single_type(typeName) || union_type(typeName);
      if (extAttrs.length && ret) ret.extAttrs = extAttrs;
      return ret;
    }

    function argument() {
      const start_position = consume_position;
      const ret = { optional: false, variadic: false, default: null };
      ret.extAttrs = extended_attrs();
      const opt_token = consume("optional");
      if (opt_token) {
        ret.optional = true;
      }
      ret.idlType = type_with_extended_attributes("argument-type");
      if (!ret.idlType) {
        unconsume(start_position);
        return;
      }
      if (!ret.optional && consume("...")) {
        ret.variadic = true;
      }
      const name = consume(ID, ...argumentNameKeywords);
      if (!name) {
        unconsume(start_position);
        return;
      }
      ret.name = unescape(name.value);
      ret.escapedName = name.value;
      if (ret.optional) {
        ret.default = default_() || null;
      }
      return ret;
    }

    function argument_list() {
      const ret = [];
      const arg = argument();
      if (!arg) return ret;
      ret.push(arg);
      while (true) {
        if (!consume(",")) return ret;
        const nxt = argument() || error("Trailing comma in arguments list");
        ret.push(nxt);
      }
    }

    function simple_extended_attr() {
      const name = consume(ID);
      if (!name) return;
      const ret = {
        name: name.value,
        arguments: null,
        type: "extended-attribute",
        rhs: null
      };
      const eq = consume("=");
      if (eq) {
        ret.rhs = consume(ID, FLOAT, INT, STR);
        if (ret.rhs) {
          // No trivia exposure yet
          ret.rhs.trivia = undefined;
        }
      }
      if (consume("(")) {
        if (eq && !ret.rhs) {
          // [Exposed=(Window,Worker)]
          ret.rhs = {
            type: "identifier-list",
            value: identifiers()
          };
        }
        else {
          // [NamedConstructor=Audio(DOMString src)] or [Constructor(DOMString str)]
          ret.arguments = argument_list();
        }
        consume(")") || error("Unexpected token in extended attribute argument list");
      }
      if (eq && !ret.rhs) error("No right hand side to extended attribute assignment");
      return ret;
    }

    // Note: we parse something simpler than the official syntax. It's all that ever
    // seems to be used
    function extended_attrs() {
      const eas = [];
      if (!consume("[")) return eas;
      eas[0] = simple_extended_attr() || error("Extended attribute with not content");
      while (consume(",")) {
        eas.push(simple_extended_attr() || error("Trailing comma in extended attribute"));
      }
      consume("]") || error("No end of extended attribute");
      return eas;
    }

    function default_() {
      if (consume("=")) {
        const def = const_value();
        if (def) {
          return def;
        } else if (consume("[")) {
          if (!consume("]")) error("Default sequence value must be empty");
          return { type: "sequence", value: [] };
        } else {
          const str = consume(STR) || error("No value for default");
          str.value = str.value.slice(1, -1);
          // No trivia exposure yet
          str.trivia = undefined;
          return str;
        }
      }
    }

    function const_() {
      if (!consume("const")) return;
      const ret = { type: "const", nullable: false };
      let typ = primitive_type();
      if (!typ) {
        typ = consume(ID) || error("No type for const");
        typ = typ.value;
      }
      ret.idlType = Object.assign({ type: "const-type" }, EMPTY_IDLTYPE, { idlType: typ });
      type_suffix(ret);
      const name = consume(ID) || error("No name for const");
      ret.name = name.value;
      consume("=") || error("No value assignment for const");
      const cnt = const_value();
      if (cnt) ret.value = cnt;
      else error("No value for const");
      consume(";") || error("Unterminated const");
      return ret;
    }

    function inheritance() {
      if (consume(":")) {
        const inh = consume(ID) || error("No type in inheritance");
        return inh.value;
      }
    }

    function operation_rest(ret) {
      if (!ret) ret = {};
      const name = consume(ID);
      ret.name = name ? unescape(name.value) : null;
      ret.escapedName = name ? name.value : null;
      consume("(") || error("Invalid operation");
      ret.arguments = argument_list();
      consume(")") || error("Unterminated operation");
      consume(";") || error("Unterminated operation");
      return ret;
    }

    function callback() {
      let ret;
      if (!consume("callback")) return;
      const tok = consume("interface");
      if (tok) {
        ret = interface_rest(false, "callback interface");
        return ret;
      }
      const name = consume(ID) || error("No name for callback");
      ret = current = { type: "callback", name: sanitize_name(name.value, "callback") };
      consume("=") || error("No assignment in callback");
      ret.idlType = return_type() || error("Missing return type");
      consume("(") || error("No arguments in callback");
      ret.arguments = argument_list();
      consume(")") || error("Unterminated callback");
      consume(";") || error("Unterminated callback");
      return ret;
    }

    function attribute({ noInherit = false, readonly = false } = {}) {
      const start_position = consume_position;
      const ret = {
        type: "attribute",
        static: false,
        stringifier: false,
        inherit: false,
        readonly: false
      };
      if (!noInherit && consume("inherit")) {
        ret.inherit = true;
      }
      if (consume("readonly")) {
        ret.readonly = true;
      } else if (readonly && probe("attribute")) {
        error("Attributes must be readonly in this context");
      }
      const rest = attribute_rest(ret);
      if (!rest) {
        unconsume(start_position);
      }
      return rest;
    }

    function attribute_rest(ret) {
      if (!consume("attribute")) {
        return;
      }
      ret.idlType = type_with_extended_attributes("attribute-type") || error("No type in attribute");
      if (ret.idlType.generic === "sequence") error("Attributes cannot accept sequence types");
      if (ret.idlType.generic === "record") error("Attributes cannot accept record types");
      const name = consume(ID, "required") || error("No name in attribute");
      ret.name = unescape(name.value);
      ret.escapedName = name.value;
      consume(";") || error("Unterminated attribute");
      return ret;
    }

    function return_type(typeName) {
      const typ = type(typeName || "return-type");
      if (typ) {
        return typ;
      }
      if (consume("void")) {
        return Object.assign({ type: "return-type" }, EMPTY_IDLTYPE, { idlType: "void" });
      }
    }

    function operation({ regular = false } = {}) {
      const ret = Object.assign({}, EMPTY_OPERATION);
      while (!regular) {
        if (consume("getter")) ret.getter = true;
        else if (consume("setter")) ret.setter = true;
        else if (consume("deleter")) ret.deleter = true;
        else break;
      }
      ret.idlType = return_type() || error("Missing return type");
      operation_rest(ret);
      return ret;
    }

    function static_member() {
      if (!consume("static")) return;
      const member = attribute({ noInherit: true }) ||
        operation({ regular: true }) ||
        error("No body in static member");
      member.static = true;
      return member;
    }

    function stringifier() {
      if (!consume("stringifier")) return;
      if (consume(";")) {
        return Object.assign({}, EMPTY_OPERATION, { stringifier: true });
      }
      const member = attribute({ noInherit: true }) ||
        operation({ regular: true }) ||
        error("Unterminated stringifier");
      member.stringifier = true;
      return member;
    }

    function identifiers() {
      const arr = [];
      const id = consume(ID);
      if (id) {
        arr.push(id.value);
      }
      else error("Expected identifiers but not found");
      while (true) {
        if (consume(",")) {
          const name = consume(ID) || error("Trailing comma in identifiers list");
          arr.push(name.value);
        } else break;
      }
      return arr;
    }

    function iterable_type() {
      if (consume("iterable")) return "iterable";
      else if (consume("legacyiterable")) return "legacyiterable";
      else if (consume("maplike")) return "maplike";
      else if (consume("setlike")) return "setlike";
      else return;
    }

    function readonly_iterable_type() {
      if (consume("maplike")) return "maplike";
      else if (consume("setlike")) return "setlike";
      else return;
    }

    function iterable() {
      const start_position = consume_position;
      const ret = { type: null, idlType: null, readonly: false };
      if (consume("readonly")) {
        ret.readonly = true;
      }
      const consumeItType = ret.readonly ? readonly_iterable_type : iterable_type;

      const ittype = consumeItType();
      if (!ittype) {
        unconsume(start_position);
        return;
      }

      const secondTypeRequired = ittype === "maplike";
      const secondTypeAllowed = secondTypeRequired || ittype === "iterable";
      ret.type = ittype;
      if (ret.type !== 'maplike' && ret.type !== 'setlike')
        delete ret.readonly;
      if (consume("<")) {
        ret.idlType = [type_with_extended_attributes()] || error(`Error parsing ${ittype} declaration`);
        if (secondTypeAllowed) {
          if (consume(",")) {
            ret.idlType.push(type_with_extended_attributes());
          }
          else if (secondTypeRequired)
            error(`Missing second type argument in ${ittype} declaration`);
        }
        if (!consume(">")) error(`Unterminated ${ittype} declaration`);
        if (!consume(";")) error(`Missing semicolon after ${ittype} declaration`);
      } else
        error(`Error parsing ${ittype} declaration`);

      return ret;
    }

    function interface_rest(isPartial, typeName = "interface") {
      const name = consume(ID) || error("No name for interface");
      const mems = [];
      const ret = current = {
        type: typeName,
        name: isPartial ? name.value : sanitize_name(name.value, "interface"),
        partial: isPartial,
        members: mems
      };
      if (!isPartial) ret.inheritance = inheritance() || null;
      consume("{") || error("Bodyless interface");
      while (true) {
        if (consume("}")) {
          consume(";") || error("Missing semicolon after interface");
          return ret;
        }
        const ea = extended_attrs();
        const mem = const_() ||
          static_member() ||
          stringifier() ||
          iterable() ||
          attribute() ||
          operation() ||
          error("Unknown member");
        mem.extAttrs = ea;
        ret.members.push(mem);
      }
    }

    function mixin_rest(isPartial) {
      if (!consume("mixin")) return;
      const name = consume(ID) || error("No name for interface mixin");
      const mems = [];
      const ret = current = {
        type: "interface mixin",
        name: isPartial ? name.value : sanitize_name(name.value, "interface mixin"),
        partial: isPartial,
        members: mems
      };
      consume("{") || error("Bodyless interface mixin");
      while (true) {
        if (consume("}")) {
          consume(";") || error("Missing semicolon after interface mixin");
          return ret;
        }
        const ea = extended_attrs();
        const mem = const_() ||
          stringifier() ||
          attribute({ noInherit: true }) ||
          operation({ regular: true }) ||
          error("Unknown member");
        mem.extAttrs = ea;
        ret.members.push(mem);
      }
    }

    function interface_(isPartial) {
      if (!consume("interface")) return;
      return mixin_rest(isPartial) ||
        interface_rest(isPartial) ||
        error("Interface has no proper body");
    }

    function namespace(isPartial) {
      if (!consume("namespace")) return;
      const name = consume(ID) || error("No name for namespace");
      const mems = [];
      const ret = current = {
        type: "namespace",
        name: isPartial ? name.value : sanitize_name(name.value, "namespace"),
        partial: isPartial,
        members: mems
      };
      consume("{") || error("Bodyless namespace");
      while (true) {
        if (consume("}")) {
          consume(";") || error("Missing semicolon after namespace");
          return ret;
        }
        const ea = extended_attrs();
        const mem = attribute({ noInherit: true, readonly: true }) ||
          operation({ regular: true }) ||
          error("Unknown member");
        mem.extAttrs = ea;
        ret.members.push(mem);
      }
    }

    function partial() {
      if (!consume("partial")) return;
      const thing = dictionary(true) ||
        interface_(true) ||
        namespace(true) ||
        error("Partial doesn't apply to anything");
      return thing;
    }

    function dictionary(isPartial) {
      if (!consume("dictionary")) return;
      const name = consume(ID) || error("No name for dictionary");
      const mems = [];
      const ret = current = {
        type: "dictionary",
        name: isPartial ? name.value : sanitize_name(name.value, "dictionary"),
        partial: isPartial,
        members: mems
      };
      if (!isPartial) ret.inheritance = inheritance() || null;
      consume("{") || error("Bodyless dictionary");
      while (true) {
        if (consume("}")) {
          consume(";") || error("Missing semicolon after dictionary");
          return ret;
        }
        const ea = extended_attrs();
        const required = consume("required");
        const typ = type_with_extended_attributes("dictionary-type") || error("No type for dictionary member");
        const name = consume(ID) || error("No name for dictionary member");
        const dflt = default_() || null;
        if (required && dflt) error("Required member must not have a default");
        const member = {
          type: "field",
          name: unescape(name.value),
          escapedName: name.value,
          required: !!required,
          idlType: typ,
          extAttrs: ea,
          default: dflt
        };
        ret.members.push(member);
        consume(";") || error("Unterminated dictionary member");
      }
    }

    function enum_() {
      if (!consume("enum")) return;
      const name = consume(ID) || error("No name for enum");
      const vals = [];
      const ret = current = {
        type: "enum",
        name: sanitize_name(name.value, "enum"),
        values: vals
      };
      consume("{") || error("No curly for enum");
      let value_expected = true;
      while (true) {
        if (consume("}")) {
          if (!ret.values.length) error("No value in enum");
          consume(";") || error("No semicolon after enum");
          return ret;
        }
        else if (!value_expected) {
          error("No comma between enum values");
        }
        const val = consume(STR) || error("Unexpected value in enum");
        val.value = val.value.slice(1, -1);
        // No trivia exposure yet
        val.trivia = undefined;
        ret.values.push(val);
        value_expected = !!consume(",");
      }
    }

    function typedef() {
      if (!consume("typedef")) return;
      const ret = {
        type: "typedef"
      };
      ret.idlType = type_with_extended_attributes("typedef-type") || error("No type in typedef");
      const name = consume(ID) || error("No name in typedef");
      ret.name = sanitize_name(name.value, "typedef");
      current = ret;
      consume(";") || error("Unterminated typedef");
      return ret;
    }

    function implements_() {
      const start_position = consume_position;
      const target = consume(ID);
      if (!target) return;
      if (consume("implements")) {
        const ret = {
          type: "implements",
          target: target.value
        };
        const imp = consume(ID) || error("Incomplete implements statement");
        ret.implements = imp.value;
        consume(";") || error("No terminating ; for implements statement");
        return ret;
      } else {
        // rollback
        unconsume(start_position);
      }
    }

    function includes() {
      const start_position = consume_position;
      const target = consume(ID);
      if (!target) return;
      if (consume("includes")) {
        const ret = {
          type: "includes",
          target: target.value
        };
        const imp = consume(ID) || error("Incomplete includes statement");
        ret.includes = imp.value;
        consume(";") || error("No terminating ; for includes statement");
        return ret;
      } else {
        // rollback
        unconsume(start_position);
      }
    }

    function definition() {
      return callback() ||
        interface_(false) ||
        partial() ||
        dictionary(false) ||
        enum_() ||
        typedef() ||
        implements_() ||
        includes() ||
        namespace(false);
    }

    function definitions() {
      if (!tokens.length) return [];
      const defs = [];
      while (true) {
        const ea = extended_attrs();
        const def = definition();
        if (!def) {
          if (ea.length) error("Stray extended attributes");
          break;
        }
        def.extAttrs = ea;
        defs.push(def);
      }
      return defs;
    }
    const res = definitions();
    if (consume_position < tokens.length) error("Unrecognised tokens");
    return res;
  }

  const obj = {
    parse(str) {
      const tokens = tokenise(str);
      return parse(tokens);
    }
  };

  if (typeof module !== 'undefined' && typeof module.exports !== 'undefined') {
    module.exports = obj;
  } else if (typeof define === 'function' && define.amd) {
    define([], () => obj);
  } else {
    (self || window).WebIDL2 = obj;
  }
})();