refactor: Use ES modules for internal runtime code (#17648)

This PR refactors all internal js files (except core) to be written as
ES modules.
`__bootstrap`has been mostly replaced with static imports in form in
`internal:[path to file from repo root]`.
To specify if files are ESM, an `esm` method has been added to
`Extension`, similar to the `js` method.
A new ModuleLoader called `InternalModuleLoader` has been added to
enable the loading of internal specifiers, which is used in all
situations except when a snapshot is only loaded, and not a new one is
created from it.

---------

Co-authored-by: Bartek Iwańczuk <biwanczuk@gmail.com>

1 files changed, 994 insertions, 998 deletions

diff --git a/ext/webidl/00_webidl.js b/ext/webidl/00_webidl.js
index bb90d973e..1357d308e 100644
--- a/ext/webidl/00_webidl.js
+++ b/ext/webidl/00_webidl.js
@@ -6,1186 +6,1182 @@
 
 /// <reference path="../../core/internal.d.ts" />
 
-"use strict";
-
-((window) => {
-  const core = window.Deno.core;
-  const {
-    ArrayBufferPrototype,
-    ArrayBufferIsView,
-    ArrayPrototypeForEach,
-    ArrayPrototypePush,
-    ArrayPrototypeSort,
-    ArrayIteratorPrototype,
-    BigInt,
-    BigIntAsIntN,
-    BigIntAsUintN,
-    Float32Array,
-    Float64Array,
-    FunctionPrototypeBind,
-    Int16Array,
-    Int32Array,
-    Int8Array,
-    isNaN,
-    MathFloor,
-    MathFround,
-    MathMax,
-    MathMin,
-    MathPow,
-    MathRound,
-    MathTrunc,
-    Number,
-    NumberIsFinite,
-    NumberIsNaN,
-    // deno-lint-ignore camelcase
-    NumberMAX_SAFE_INTEGER,
-    // deno-lint-ignore camelcase
-    NumberMIN_SAFE_INTEGER,
-    ObjectAssign,
-    ObjectCreate,
-    ObjectDefineProperties,
-    ObjectDefineProperty,
-    ObjectGetOwnPropertyDescriptor,
-    ObjectGetOwnPropertyDescriptors,
-    ObjectGetPrototypeOf,
-    ObjectPrototypeHasOwnProperty,
-    ObjectPrototypeIsPrototypeOf,
-    ObjectIs,
-    PromisePrototypeThen,
-    PromiseReject,
-    PromiseResolve,
-    ReflectApply,
-    ReflectDefineProperty,
-    ReflectGetOwnPropertyDescriptor,
-    ReflectHas,
-    ReflectOwnKeys,
-    RegExpPrototypeTest,
-    Set,
-    SetPrototypeEntries,
-    SetPrototypeForEach,
-    SetPrototypeKeys,
-    SetPrototypeValues,
-    SetPrototypeHas,
-    SetPrototypeClear,
-    SetPrototypeDelete,
-    SetPrototypeAdd,
-    // TODO(lucacasonato): add SharedArrayBuffer to primordials
-    // SharedArrayBufferPrototype
-    String,
-    StringFromCodePoint,
-    StringPrototypeCharCodeAt,
-    Symbol,
-    SymbolIterator,
-    SymbolToStringTag,
-    TypedArrayPrototypeGetSymbolToStringTag,
-    TypeError,
-    Uint16Array,
-    Uint32Array,
-    Uint8Array,
-    Uint8ClampedArray,
-  } = window.__bootstrap.primordials;
+const core = globalThis.Deno.core;
+const primordials = globalThis.__bootstrap.primordials;
+const {
+  ArrayBufferPrototype,
+  ArrayBufferIsView,
+  ArrayPrototypeForEach,
+  ArrayPrototypePush,
+  ArrayPrototypeSort,
+  ArrayIteratorPrototype,
+  BigInt,
+  BigIntAsIntN,
+  BigIntAsUintN,
+  Float32Array,
+  Float64Array,
+  FunctionPrototypeBind,
+  Int16Array,
+  Int32Array,
+  Int8Array,
+  isNaN,
+  MathFloor,
+  MathFround,
+  MathMax,
+  MathMin,
+  MathPow,
+  MathRound,
+  MathTrunc,
+  Number,
+  NumberIsFinite,
+  NumberIsNaN,
+  // deno-lint-ignore camelcase
+  NumberMAX_SAFE_INTEGER,
+  // deno-lint-ignore camelcase
+  NumberMIN_SAFE_INTEGER,
+  ObjectAssign,
+  ObjectCreate,
+  ObjectDefineProperties,
+  ObjectDefineProperty,
+  ObjectGetOwnPropertyDescriptor,
+  ObjectGetOwnPropertyDescriptors,
+  ObjectGetPrototypeOf,
+  ObjectPrototypeHasOwnProperty,
+  ObjectPrototypeIsPrototypeOf,
+  ObjectIs,
+  PromisePrototypeThen,
+  PromiseReject,
+  PromiseResolve,
+  ReflectApply,
+  ReflectDefineProperty,
+  ReflectGetOwnPropertyDescriptor,
+  ReflectHas,
+  ReflectOwnKeys,
+  RegExpPrototypeTest,
+  Set,
+  SetPrototypeEntries,
+  SetPrototypeForEach,
+  SetPrototypeKeys,
+  SetPrototypeValues,
+  SetPrototypeHas,
+  SetPrototypeClear,
+  SetPrototypeDelete,
+  SetPrototypeAdd,
+  // TODO(lucacasonato): add SharedArrayBuffer to primordials
+  // SharedArrayBufferPrototype
+  String,
+  StringFromCodePoint,
+  StringPrototypeCharCodeAt,
+  Symbol,
+  SymbolIterator,
+  SymbolToStringTag,
+  TypedArrayPrototypeGetSymbolToStringTag,
+  TypeError,
+  Uint16Array,
+  Uint32Array,
+  Uint8Array,
+  Uint8ClampedArray,
+} = primordials;
+
+function makeException(ErrorType, message, opts = {}) {
+  return new ErrorType(
+    `${opts.prefix ? opts.prefix + ": " : ""}${
+      opts.context ? opts.context : "Value"
+    } ${message}`,
+  );
+}
 
-  function makeException(ErrorType, message, opts = {}) {
-    return new ErrorType(
-      `${opts.prefix ? opts.prefix + ": " : ""}${
-        opts.context ? opts.context : "Value"
-      } ${message}`,
-    );
+function toNumber(value) {
+  if (typeof value === "bigint") {
+    throw TypeError("Cannot convert a BigInt value to a number");
   }
+  return Number(value);
+}
 
-  function toNumber(value) {
-    if (typeof value === "bigint") {
-      throw TypeError("Cannot convert a BigInt value to a number");
-    }
-    return Number(value);
+function type(V) {
+  if (V === null) {
+    return "Null";
   }
+  switch (typeof V) {
+    case "undefined":
+      return "Undefined";
+    case "boolean":
+      return "Boolean";
+    case "number":
+      return "Number";
+    case "string":
+      return "String";
+    case "symbol":
+      return "Symbol";
+    case "bigint":
+      return "BigInt";
+    case "object":
+    // Falls through
+    case "function":
+    // Falls through
+    default:
+      // Per ES spec, typeof returns an implemention-defined value that is not any of the existing ones for
+      // uncallable non-standard exotic objects. Yet Type() which the Web IDL spec depends on returns Object for
+      // such cases. So treat the default case as an object.
+      return "Object";
+  }
+}
 
-  function type(V) {
-    if (V === null) {
-      return "Null";
-    }
-    switch (typeof V) {
-      case "undefined":
-        return "Undefined";
-      case "boolean":
-        return "Boolean";
-      case "number":
-        return "Number";
-      case "string":
-        return "String";
-      case "symbol":
-        return "Symbol";
-      case "bigint":
-        return "BigInt";
-      case "object":
-      // Falls through
-      case "function":
-      // Falls through
-      default:
-        // Per ES spec, typeof returns an implemention-defined value that is not any of the existing ones for
-        // uncallable non-standard exotic objects. Yet Type() which the Web IDL spec depends on returns Object for
-        // such cases. So treat the default case as an object.
-        return "Object";
-    }
+// Round x to the nearest integer, choosing the even integer if it lies halfway between two.
+function evenRound(x) {
+  // There are four cases for numbers with fractional part being .5:
+  //
+  // case |     x     | floor(x) | round(x) | expected | x <> 0 | x % 1 | x & 1 |   example
+  //   1  |  2n + 0.5 |  2n      |  2n + 1  |  2n      |   >    |  0.5  |   0   |  0.5 ->  0
+  //   2  |  2n + 1.5 |  2n + 1  |  2n + 2  |  2n + 2  |   >    |  0.5  |   1   |  1.5 ->  2
+  //   3  | -2n - 0.5 | -2n - 1  | -2n      | -2n      |   <    | -0.5  |   0   | -0.5 ->  0
+  //   4  | -2n - 1.5 | -2n - 2  | -2n - 1  | -2n - 2  |   <    | -0.5  |   1   | -1.5 -> -2
+  // (where n is a non-negative integer)
+  //
+  // Branch here for cases 1 and 4
+  if (
+    (x > 0 && x % 1 === +0.5 && (x & 1) === 0) ||
+    (x < 0 && x % 1 === -0.5 && (x & 1) === 1)
+  ) {
+    return censorNegativeZero(MathFloor(x));
   }
 
-  // Round x to the nearest integer, choosing the even integer if it lies halfway between two.
-  function evenRound(x) {
-    // There are four cases for numbers with fractional part being .5:
-    //
-    // case |     x     | floor(x) | round(x) | expected | x <> 0 | x % 1 | x & 1 |   example
-    //   1  |  2n + 0.5 |  2n      |  2n + 1  |  2n      |   >    |  0.5  |   0   |  0.5 ->  0
-    //   2  |  2n + 1.5 |  2n + 1  |  2n + 2  |  2n + 2  |   >    |  0.5  |   1   |  1.5 ->  2
-    //   3  | -2n - 0.5 | -2n - 1  | -2n      | -2n      |   <    | -0.5  |   0   | -0.5 ->  0
-    //   4  | -2n - 1.5 | -2n - 2  | -2n - 1  | -2n - 2  |   <    | -0.5  |   1   | -1.5 -> -2
-    // (where n is a non-negative integer)
-    //
-    // Branch here for cases 1 and 4
-    if (
-      (x > 0 && x % 1 === +0.5 && (x & 1) === 0) ||
-      (x < 0 && x % 1 === -0.5 && (x & 1) === 1)
-    ) {
-      return censorNegativeZero(MathFloor(x));
-    }
+  return censorNegativeZero(MathRound(x));
+}
 
-    return censorNegativeZero(MathRound(x));
-  }
+function integerPart(n) {
+  return censorNegativeZero(MathTrunc(n));
+}
 
-  function integerPart(n) {
-    return censorNegativeZero(MathTrunc(n));
-  }
+function sign(x) {
+  return x < 0 ? -1 : 1;
+}
 
-  function sign(x) {
-    return x < 0 ? -1 : 1;
+function modulo(x, y) {
+  // https://tc39.github.io/ecma262/#eqn-modulo
+  // Note that http://stackoverflow.com/a/4467559/3191 does NOT work for large modulos
+  const signMightNotMatch = x % y;
+  if (sign(y) !== sign(signMightNotMatch)) {
+    return signMightNotMatch + y;
   }
-
-  function modulo(x, y) {
-    // https://tc39.github.io/ecma262/#eqn-modulo
-    // Note that http://stackoverflow.com/a/4467559/3191 does NOT work for large modulos
-    const signMightNotMatch = x % y;
-    if (sign(y) !== sign(signMightNotMatch)) {
-      return signMightNotMatch + y;
-    }
-    return signMightNotMatch;
+  return signMightNotMatch;
+}
+
+function censorNegativeZero(x) {
+  return x === 0 ? 0 : x;
+}
+
+function createIntegerConversion(bitLength, typeOpts) {
+  const isSigned = !typeOpts.unsigned;
+
+  let lowerBound;
+  let upperBound;
+  if (bitLength === 64) {
+    upperBound = NumberMAX_SAFE_INTEGER;
+    lowerBound = !isSigned ? 0 : NumberMIN_SAFE_INTEGER;
+  } else if (!isSigned) {
+    lowerBound = 0;
+    upperBound = MathPow(2, bitLength) - 1;
+  } else {
+    lowerBound = -MathPow(2, bitLength - 1);
+    upperBound = MathPow(2, bitLength - 1) - 1;
   }
 
-  function censorNegativeZero(x) {
-    return x === 0 ? 0 : x;
-  }
+  const twoToTheBitLength = MathPow(2, bitLength);
+  const twoToOneLessThanTheBitLength = MathPow(2, bitLength - 1);
 
-  function createIntegerConversion(bitLength, typeOpts) {
-    const isSigned = !typeOpts.unsigned;
-
-    let lowerBound;
-    let upperBound;
-    if (bitLength === 64) {
-      upperBound = NumberMAX_SAFE_INTEGER;
-      lowerBound = !isSigned ? 0 : NumberMIN_SAFE_INTEGER;
-    } else if (!isSigned) {
-      lowerBound = 0;
-      upperBound = MathPow(2, bitLength) - 1;
-    } else {
-      lowerBound = -MathPow(2, bitLength - 1);
-      upperBound = MathPow(2, bitLength - 1) - 1;
+  return (V, opts = {}) => {
+    let x = toNumber(V);
+    x = censorNegativeZero(x);
+
+    if (opts.enforceRange) {
+      if (!NumberIsFinite(x)) {
+        throw makeException(TypeError, "is not a finite number", opts);
+      }
+
+      x = integerPart(x);
+
+      if (x < lowerBound || x > upperBound) {
+        throw makeException(
+          TypeError,
+          `is outside the accepted range of ${lowerBound} to ${upperBound}, inclusive`,
+          opts,
+        );
+      }
+
+      return x;
     }
 
-    const twoToTheBitLength = MathPow(2, bitLength);
-    const twoToOneLessThanTheBitLength = MathPow(2, bitLength - 1);
+    if (!NumberIsNaN(x) && opts.clamp) {
+      x = MathMin(MathMax(x, lowerBound), upperBound);
+      x = evenRound(x);
+      return x;
+    }
 
-    return (V, opts = {}) => {
-      let x = toNumber(V);
-      x = censorNegativeZero(x);
+    if (!NumberIsFinite(x) || x === 0) {
+      return 0;
+    }
+    x = integerPart(x);
 
-      if (opts.enforceRange) {
-        if (!NumberIsFinite(x)) {
-          throw makeException(TypeError, "is not a finite number", opts);
-        }
+    // Math.pow(2, 64) is not accurately representable in JavaScript, so try to avoid these per-spec operations if
+    // possible. Hopefully it's an optimization for the non-64-bitLength cases too.
+    if (x >= lowerBound && x <= upperBound) {
+      return x;
+    }
 
-        x = integerPart(x);
+    // These will not work great for bitLength of 64, but oh well. See the README for more details.
+    x = modulo(x, twoToTheBitLength);
+    if (isSigned && x >= twoToOneLessThanTheBitLength) {
+      return x - twoToTheBitLength;
+    }
+    return x;
+  };
+}
 
-        if (x < lowerBound || x > upperBound) {
-          throw makeException(
-            TypeError,
-            `is outside the accepted range of ${lowerBound} to ${upperBound}, inclusive`,
-            opts,
-          );
-        }
+function createLongLongConversion(bitLength, { unsigned }) {
+  const upperBound = NumberMAX_SAFE_INTEGER;
+  const lowerBound = unsigned ? 0 : NumberMIN_SAFE_INTEGER;
+  const asBigIntN = unsigned ? BigIntAsUintN : BigIntAsIntN;
 
-        return x;
-      }
+  return (V, opts = {}) => {
+    let x = toNumber(V);
+    x = censorNegativeZero(x);
 
-      if (!NumberIsNaN(x) && opts.clamp) {
-        x = MathMin(MathMax(x, lowerBound), upperBound);
-        x = evenRound(x);
-        return x;
+    if (opts.enforceRange) {
+      if (!NumberIsFinite(x)) {
+        throw makeException(TypeError, "is not a finite number", opts);
       }
 
-      if (!NumberIsFinite(x) || x === 0) {
-        return 0;
-      }
       x = integerPart(x);
 
-      // Math.pow(2, 64) is not accurately representable in JavaScript, so try to avoid these per-spec operations if
-      // possible. Hopefully it's an optimization for the non-64-bitLength cases too.
-      if (x >= lowerBound && x <= upperBound) {
-        return x;
+      if (x < lowerBound || x > upperBound) {
+        throw makeException(
+          TypeError,
+          `is outside the accepted range of ${lowerBound} to ${upperBound}, inclusive`,
+          opts,
+        );
       }
 
-      // These will not work great for bitLength of 64, but oh well. See the README for more details.
-      x = modulo(x, twoToTheBitLength);
-      if (isSigned && x >= twoToOneLessThanTheBitLength) {
-        return x - twoToTheBitLength;
-      }
       return x;
-    };
-  }
+    }
 
-  function createLongLongConversion(bitLength, { unsigned }) {
-    const upperBound = NumberMAX_SAFE_INTEGER;
-    const lowerBound = unsigned ? 0 : NumberMIN_SAFE_INTEGER;
-    const asBigIntN = unsigned ? BigIntAsUintN : BigIntAsIntN;
+    if (!NumberIsNaN(x) && opts.clamp) {
+      x = MathMin(MathMax(x, lowerBound), upperBound);
+      x = evenRound(x);
+      return x;
+    }
 
-    return (V, opts = {}) => {
-      let x = toNumber(V);
-      x = censorNegativeZero(x);
+    if (!NumberIsFinite(x) || x === 0) {
+      return 0;
+    }
 
-      if (opts.enforceRange) {
-        if (!NumberIsFinite(x)) {
-          throw makeException(TypeError, "is not a finite number", opts);
-        }
+    let xBigInt = BigInt(integerPart(x));
+    xBigInt = asBigIntN(bitLength, xBigInt);
+    return Number(xBigInt);
+  };
+}
 
-        x = integerPart(x);
+const converters = [];
 
-        if (x < lowerBound || x > upperBound) {
-          throw makeException(
-            TypeError,
-            `is outside the accepted range of ${lowerBound} to ${upperBound}, inclusive`,
-            opts,
-          );
-        }
+converters.any = (V) => {
+  return V;
+};
 
-        return x;
-      }
+converters.boolean = function (val) {
+  return !!val;
+};
 
-      if (!NumberIsNaN(x) && opts.clamp) {
-        x = MathMin(MathMax(x, lowerBound), upperBound);
-        x = evenRound(x);
-        return x;
-      }
+converters.byte = createIntegerConversion(8, { unsigned: false });
+converters.octet = createIntegerConversion(8, { unsigned: true });
 
-      if (!NumberIsFinite(x) || x === 0) {
-        return 0;
-      }
+converters.short = createIntegerConversion(16, { unsigned: false });
+converters["unsigned short"] = createIntegerConversion(16, {
+  unsigned: true,
+});
 
-      let xBigInt = BigInt(integerPart(x));
-      xBigInt = asBigIntN(bitLength, xBigInt);
-      return Number(xBigInt);
-    };
+converters.long = createIntegerConversion(32, { unsigned: false });
+converters["unsigned long"] = createIntegerConversion(32, { unsigned: true });
+
+converters["long long"] = createLongLongConversion(64, { unsigned: false });
+converters["unsigned long long"] = createLongLongConversion(64, {
+  unsigned: true,
+});
+
+converters.float = (V, opts) => {
+  const x = toNumber(V);
+
+  if (!NumberIsFinite(x)) {
+    throw makeException(
+      TypeError,
+      "is not a finite floating-point value",
+      opts,
+    );
   }
 
-  const converters = [];
+  if (ObjectIs(x, -0)) {
+    return x;
+  }
 
-  converters.any = (V) => {
-    return V;
-  };
+  const y = MathFround(x);
 
-  converters.boolean = function (val) {
-    return !!val;
-  };
+  if (!NumberIsFinite(y)) {
+    throw makeException(
+      TypeError,
+      "is outside the range of a single-precision floating-point value",
+      opts,
+    );
+  }
 
-  converters.byte = createIntegerConversion(8, { unsigned: false });
-  converters.octet = createIntegerConversion(8, { unsigned: true });
+  return y;
+};
 
-  converters.short = createIntegerConversion(16, { unsigned: false });
-  converters["unsigned short"] = createIntegerConversion(16, {
-    unsigned: true,
-  });
+converters["unrestricted float"] = (V, _opts) => {
+  const x = toNumber(V);
 
-  converters.long = createIntegerConversion(32, { unsigned: false });
-  converters["unsigned long"] = createIntegerConversion(32, { unsigned: true });
+  if (isNaN(x)) {
+    return x;
+  }
 
-  converters["long long"] = createLongLongConversion(64, { unsigned: false });
-  converters["unsigned long long"] = createLongLongConversion(64, {
-    unsigned: true,
-  });
+  if (ObjectIs(x, -0)) {
+    return x;
+  }
 
-  converters.float = (V, opts) => {
-    const x = toNumber(V);
+  return MathFround(x);
+};
 
-    if (!NumberIsFinite(x)) {
-      throw makeException(
-        TypeError,
-        "is not a finite floating-point value",
-        opts,
-      );
-    }
+converters.double = (V, opts) => {
+  const x = toNumber(V);
 
-    if (ObjectIs(x, -0)) {
-      return x;
-    }
+  if (!NumberIsFinite(x)) {
+    throw makeException(
+      TypeError,
+      "is not a finite floating-point value",
+      opts,
+    );
+  }
 
-    const y = MathFround(x);
+  return x;
+};
 
-    if (!NumberIsFinite(y)) {
-      throw makeException(
-        TypeError,
-        "is outside the range of a single-precision floating-point value",
-        opts,
-      );
-    }
+converters["unrestricted double"] = (V, _opts) => {
+  const x = toNumber(V);
 
-    return y;
-  };
+  return x;
+};
 
-  converters["unrestricted float"] = (V, _opts) => {
-    const x = toNumber(V);
+converters.DOMString = function (V, opts = {}) {
+  if (typeof V === "string") {
+    return V;
+  } else if (V === null && opts.treatNullAsEmptyString) {
+    return "";
+  } else if (typeof V === "symbol") {
+    throw makeException(
+      TypeError,
+      "is a symbol, which cannot be converted to a string",
+      opts,
+    );
+  }
 
-    if (isNaN(x)) {
-      return x;
-    }
+  return String(V);
+};
 
-    if (ObjectIs(x, -0)) {
-      return x;
+// deno-lint-ignore no-control-regex
+const IS_BYTE_STRING = /^[\x00-\xFF]*$/;
+converters.ByteString = (V, opts) => {
+  const x = converters.DOMString(V, opts);
+  if (!RegExpPrototypeTest(IS_BYTE_STRING, x)) {
+    throw makeException(TypeError, "is not a valid ByteString", opts);
+  }
+  return x;
+};
+
+converters.USVString = (V, opts) => {
+  const S = converters.DOMString(V, opts);
+  const n = S.length;
+  let U = "";
+  for (let i = 0; i < n; ++i) {
+    const c = StringPrototypeCharCodeAt(S, i);
+    if (c < 0xd800 || c > 0xdfff) {
+      U += StringFromCodePoint(c);
+    } else if (0xdc00 <= c && c <= 0xdfff) {
+      U += StringFromCodePoint(0xfffd);
+    } else if (i === n - 1) {
+      U += StringFromCodePoint(0xfffd);
+    } else {
+      const d = StringPrototypeCharCodeAt(S, i + 1);
+      if (0xdc00 <= d && d <= 0xdfff) {
+        const a = c & 0x3ff;
+        const b = d & 0x3ff;
+        U += StringFromCodePoint((2 << 15) + (2 << 9) * a + b);
+        ++i;
+      } else {
+        U += StringFromCodePoint(0xfffd);
+      }
     }
+  }
+  return U;
+};
 
-    return MathFround(x);
-  };
+converters.object = (V, opts) => {
+  if (type(V) !== "Object") {
+    throw makeException(TypeError, "is not an object", opts);
+  }
 
-  converters.double = (V, opts) => {
-    const x = toNumber(V);
+  return V;
+};
 
-    if (!NumberIsFinite(x)) {
+// Not exported, but used in Function and VoidFunction.
+
+// Neither Function nor VoidFunction is defined with [TreatNonObjectAsNull], so
+// handling for that is omitted.
+function convertCallbackFunction(V, opts) {
+  if (typeof V !== "function") {
+    throw makeException(TypeError, "is not a function", opts);
+  }
+  return V;
+}
+
+function isDataView(V) {
+  return ArrayBufferIsView(V) &&
+    TypedArrayPrototypeGetSymbolToStringTag(V) === undefined;
+}
+
+function isNonSharedArrayBuffer(V) {
+  return ObjectPrototypeIsPrototypeOf(ArrayBufferPrototype, V);
+}
+
+function isSharedArrayBuffer(V) {
+  // deno-lint-ignore prefer-primordials
+  return ObjectPrototypeIsPrototypeOf(SharedArrayBuffer.prototype, V);
+}
+
+converters.ArrayBuffer = (V, opts = {}) => {
+  if (!isNonSharedArrayBuffer(V)) {
+    if (opts.allowShared && !isSharedArrayBuffer(V)) {
       throw makeException(
         TypeError,
-        "is not a finite floating-point value",
+        "is not an ArrayBuffer or SharedArrayBuffer",
         opts,
       );
     }
+    throw makeException(TypeError, "is not an ArrayBuffer", opts);
+  }
 
-    return x;
-  };
+  return V;
+};
 
-  converters["unrestricted double"] = (V, _opts) => {
-    const x = toNumber(V);
+converters.DataView = (V, opts = {}) => {
+  if (!isDataView(V)) {
+    throw makeException(TypeError, "is not a DataView", opts);
+  }
 
-    return x;
-  };
+  if (!opts.allowShared && isSharedArrayBuffer(V.buffer)) {
+    throw makeException(
+      TypeError,
+      "is backed by a SharedArrayBuffer, which is not allowed",
+      opts,
+    );
+  }
+
+  return V;
+};
+
+// Returns the unforgeable `TypedArray` constructor name or `undefined`,
+// if the `this` value isn't a valid `TypedArray` object.
+//
+// https://tc39.es/ecma262/#sec-get-%typedarray%.prototype-@@tostringtag
+const typedArrayNameGetter = ObjectGetOwnPropertyDescriptor(
+  ObjectGetPrototypeOf(Uint8Array).prototype,
+  SymbolToStringTag,
+).get;
+ArrayPrototypeForEach(
+  [
+    Int8Array,
+    Int16Array,
+    Int32Array,
+    Uint8Array,
+    Uint16Array,
+    Uint32Array,
+    Uint8ClampedArray,
+    Float32Array,
+    Float64Array,
+  ],
+  (func) => {
+    const name = func.name;
+    const article = RegExpPrototypeTest(/^[AEIOU]/, name) ? "an" : "a";
+    converters[name] = (V, opts = {}) => {
+      if (!ArrayBufferIsView(V) || typedArrayNameGetter.call(V) !== name) {
+        throw makeException(
+          TypeError,
+          `is not ${article} ${name} object`,
+          opts,
+        );
+      }
+      if (!opts.allowShared && isSharedArrayBuffer(V.buffer)) {
+        throw makeException(
+          TypeError,
+          "is a view on a SharedArrayBuffer, which is not allowed",
+          opts,
+        );
+      }
 
-  converters.DOMString = function (V, opts = {}) {
-    if (typeof V === "string") {
       return V;
-    } else if (V === null && opts.treatNullAsEmptyString) {
-      return "";
-    } else if (typeof V === "symbol") {
+    };
+  },
+);
+
+// Common definitions
+
+converters.ArrayBufferView = (V, opts = {}) => {
+  if (!ArrayBufferIsView(V)) {
+    throw makeException(
+      TypeError,
+      "is not a view on an ArrayBuffer or SharedArrayBuffer",
+      opts,
+    );
+  }
+
+  if (!opts.allowShared && isSharedArrayBuffer(V.buffer)) {
+    throw makeException(
+      TypeError,
+      "is a view on a SharedArrayBuffer, which is not allowed",
+      opts,
+    );
+  }
+
+  return V;
+};
+
+converters.BufferSource = (V, opts = {}) => {
+  if (ArrayBufferIsView(V)) {
+    if (!opts.allowShared && isSharedArrayBuffer(V.buffer)) {
       throw makeException(
         TypeError,
-        "is a symbol, which cannot be converted to a string",
+        "is a view on a SharedArrayBuffer, which is not allowed",
         opts,
       );
     }
 
-    return String(V);
-  };
+    return V;
+  }
+
+  if (!opts.allowShared && !isNonSharedArrayBuffer(V)) {
+    throw makeException(
+      TypeError,
+      "is not an ArrayBuffer or a view on one",
+      opts,
+    );
+  }
+  if (
+    opts.allowShared &&
+    !isSharedArrayBuffer(V) &&
+    !isNonSharedArrayBuffer(V)
+  ) {
+    throw makeException(
+      TypeError,
+      "is not an ArrayBuffer, SharedArrayBuffer, or a view on one",
+      opts,
+    );
+  }
 
-  // deno-lint-ignore no-control-regex
-  const IS_BYTE_STRING = /^[\x00-\xFF]*$/;
-  converters.ByteString = (V, opts) => {
-    const x = converters.DOMString(V, opts);
-    if (!RegExpPrototypeTest(IS_BYTE_STRING, x)) {
-      throw makeException(TypeError, "is not a valid ByteString", opts);
+  return V;
+};
+
+converters.DOMTimeStamp = converters["unsigned long long"];
+converters.DOMHighResTimeStamp = converters["double"];
+
+converters.Function = convertCallbackFunction;
+
+converters.VoidFunction = convertCallbackFunction;
+
+converters["UVString?"] = createNullableConverter(
+  converters.USVString,
+);
+converters["sequence<double>"] = createSequenceConverter(
+  converters.double,
+);
+converters["sequence<object>"] = createSequenceConverter(
+  converters.object,
+);
+converters["Promise<undefined>"] = createPromiseConverter(() => undefined);
+
+converters["sequence<ByteString>"] = createSequenceConverter(
+  converters.ByteString,
+);
+converters["sequence<sequence<ByteString>>"] = createSequenceConverter(
+  converters["sequence<ByteString>"],
+);
+converters["record<ByteString, ByteString>"] = createRecordConverter(
+  converters.ByteString,
+  converters.ByteString,
+);
+
+converters["sequence<USVString>"] = createSequenceConverter(
+  converters.USVString,
+);
+converters["sequence<sequence<USVString>>"] = createSequenceConverter(
+  converters["sequence<USVString>"],
+);
+converters["record<USVString, USVString>"] = createRecordConverter(
+  converters.USVString,
+  converters.USVString,
+);
+
+converters["sequence<DOMString>"] = createSequenceConverter(
+  converters.DOMString,
+);
+
+function requiredArguments(length, required, opts = {}) {
+  if (length < required) {
+    const errMsg = `${
+      opts.prefix ? opts.prefix + ": " : ""
+    }${required} argument${
+      required === 1 ? "" : "s"
+    } required, but only ${length} present.`;
+    throw new TypeError(errMsg);
+  }
+}
+
+function createDictionaryConverter(name, ...dictionaries) {
+  let hasRequiredKey = false;
+  const allMembers = [];
+  for (let i = 0; i < dictionaries.length; ++i) {
+    const members = dictionaries[i];
+    for (let j = 0; j < members.length; ++j) {
+      const member = members[j];
+      if (member.required) {
+        hasRequiredKey = true;
+      }
+      ArrayPrototypePush(allMembers, member);
     }
-    return x;
-  };
+  }
+  ArrayPrototypeSort(allMembers, (a, b) => {
+    if (a.key == b.key) {
+      return 0;
+    }
+    return a.key < b.key ? -1 : 1;
+  });
 
-  converters.USVString = (V, opts) => {
-    const S = converters.DOMString(V, opts);
-    const n = S.length;
-    let U = "";
-    for (let i = 0; i < n; ++i) {
-      const c = StringPrototypeCharCodeAt(S, i);
-      if (c < 0xd800 || c > 0xdfff) {
-        U += StringFromCodePoint(c);
-      } else if (0xdc00 <= c && c <= 0xdfff) {
-        U += StringFromCodePoint(0xfffd);
-      } else if (i === n - 1) {
-        U += StringFromCodePoint(0xfffd);
+  const defaultValues = {};
+  for (let i = 0; i < allMembers.length; ++i) {
+    const member = allMembers[i];
+    if (ReflectHas(member, "defaultValue")) {
+      const idlMemberValue = member.defaultValue;
+      const imvType = typeof idlMemberValue;
+      // Copy by value types can be directly assigned, copy by reference types
+      // need to be re-created for each allocation.
+      if (
+        imvType === "number" || imvType === "boolean" ||
+        imvType === "string" || imvType === "bigint" ||
+        imvType === "undefined"
+      ) {
+        defaultValues[member.key] = member.converter(idlMemberValue, {});
       } else {
-        const d = StringPrototypeCharCodeAt(S, i + 1);
-        if (0xdc00 <= d && d <= 0xdfff) {
-          const a = c & 0x3ff;
-          const b = d & 0x3ff;
-          U += StringFromCodePoint((2 << 15) + (2 << 9) * a + b);
-          ++i;
-        } else {
-          U += StringFromCodePoint(0xfffd);
-        }
+        ObjectDefineProperty(defaultValues, member.key, {
+          get() {
+            return member.converter(idlMemberValue, member.defaultValue);
+          },
+          enumerable: true,
+        });
       }
     }
-    return U;
-  };
+  }
 
-  converters.object = (V, opts) => {
-    if (type(V) !== "Object") {
-      throw makeException(TypeError, "is not an object", opts);
+  return function (V, opts = {}) {
+    const typeV = type(V);
+    switch (typeV) {
+      case "Undefined":
+      case "Null":
+      case "Object":
+        break;
+      default:
+        throw makeException(
+          TypeError,
+          "can not be converted to a dictionary",
+          opts,
+        );
     }
+    const esDict = V;
 
-    return V;
-  };
-
-  // Not exported, but used in Function and VoidFunction.
+    const idlDict = ObjectAssign({}, defaultValues);
 
-  // Neither Function nor VoidFunction is defined with [TreatNonObjectAsNull], so
-  // handling for that is omitted.
-  function convertCallbackFunction(V, opts) {
-    if (typeof V !== "function") {
-      throw makeException(TypeError, "is not a function", opts);
+    // NOTE: fast path Null and Undefined.
+    if ((V === undefined || V === null) && !hasRequiredKey) {
+      return idlDict;
     }
-    return V;
-  }
-
-  function isDataView(V) {
-    return ArrayBufferIsView(V) &&
-      TypedArrayPrototypeGetSymbolToStringTag(V) === undefined;
-  }
 
-  function isNonSharedArrayBuffer(V) {
-    return ObjectPrototypeIsPrototypeOf(ArrayBufferPrototype, V);
-  }
+    for (let i = 0; i < allMembers.length; ++i) {
+      const member = allMembers[i];
+      const key = member.key;
 
-  function isSharedArrayBuffer(V) {
-    // deno-lint-ignore prefer-primordials
-    return ObjectPrototypeIsPrototypeOf(SharedArrayBuffer.prototype, V);
-  }
+      let esMemberValue;
+      if (typeV === "Undefined" || typeV === "Null") {
+        esMemberValue = undefined;
+      } else {
+        esMemberValue = esDict[key];
+      }
 
-  converters.ArrayBuffer = (V, opts = {}) => {
-    if (!isNonSharedArrayBuffer(V)) {
-      if (opts.allowShared && !isSharedArrayBuffer(V)) {
+      if (esMemberValue !== undefined) {
+        const context = `'${key}' of '${name}'${
+          opts.context ? ` (${opts.context})` : ""
+        }`;
+        const converter = member.converter;
+        const idlMemberValue = converter(esMemberValue, { ...opts, context });
+        idlDict[key] = idlMemberValue;
+      } else if (member.required) {
         throw makeException(
           TypeError,
-          "is not an ArrayBuffer or SharedArrayBuffer",
+          `can not be converted to '${name}' because '${key}' is required in '${name}'.`,
           opts,
         );
       }
-      throw makeException(TypeError, "is not an ArrayBuffer", opts);
     }
 
-    return V;
+    return idlDict;
   };
+}
 
-  converters.DataView = (V, opts = {}) => {
-    if (!isDataView(V)) {
-      throw makeException(TypeError, "is not a DataView", opts);
-    }
+// https://heycam.github.io/webidl/#es-enumeration
+function createEnumConverter(name, values) {
+  const E = new Set(values);
 
-    if (!opts.allowShared && isSharedArrayBuffer(V.buffer)) {
-      throw makeException(
-        TypeError,
-        "is backed by a SharedArrayBuffer, which is not allowed",
-        opts,
+  return function (V, opts = {}) {
+    const S = String(V);
+
+    if (!E.has(S)) {
+      throw new TypeError(
+        `${
+          opts.prefix ? opts.prefix + ": " : ""
+        }The provided value '${S}' is not a valid enum value of type ${name}.`,
       );
     }
 
-    return V;
+    return S;
   };
+}
+
+function createNullableConverter(converter) {
+  return (V, opts = {}) => {
+    // FIXME: If Type(V) is not Object, and the conversion to an IDL value is
+    // being performed due to V being assigned to an attribute whose type is a
+    // nullable callback function that is annotated with
+    // [LegacyTreatNonObjectAsNull], then return the IDL nullable type T?
+    // value null.
+
+    if (V === null || V === undefined) return null;
+    return converter(V, opts);
+  };
+}
 
-  // Returns the unforgeable `TypedArray` constructor name or `undefined`,
-  // if the `this` value isn't a valid `TypedArray` object.
-  //
-  // https://tc39.es/ecma262/#sec-get-%typedarray%.prototype-@@tostringtag
-  const typedArrayNameGetter = ObjectGetOwnPropertyDescriptor(
-    ObjectGetPrototypeOf(Uint8Array).prototype,
-    SymbolToStringTag,
-  ).get;
-  ArrayPrototypeForEach(
-    [
-      Int8Array,
-      Int16Array,
-      Int32Array,
-      Uint8Array,
-      Uint16Array,
-      Uint32Array,
-      Uint8ClampedArray,
-      Float32Array,
-      Float64Array,
-    ],
-    (func) => {
-      const name = func.name;
-      const article = RegExpPrototypeTest(/^[AEIOU]/, name) ? "an" : "a";
-      converters[name] = (V, opts = {}) => {
-        if (!ArrayBufferIsView(V) || typedArrayNameGetter.call(V) !== name) {
-          throw makeException(
-            TypeError,
-            `is not ${article} ${name} object`,
-            opts,
-          );
-        }
-        if (!opts.allowShared && isSharedArrayBuffer(V.buffer)) {
-          throw makeException(
-            TypeError,
-            "is a view on a SharedArrayBuffer, which is not allowed",
-            opts,
-          );
-        }
-
-        return V;
-      };
-    },
-  );
-
-  // Common definitions
-
-  converters.ArrayBufferView = (V, opts = {}) => {
-    if (!ArrayBufferIsView(V)) {
+// https://heycam.github.io/webidl/#es-sequence
+function createSequenceConverter(converter) {
+  return function (V, opts = {}) {
+    if (type(V) !== "Object") {
       throw makeException(
         TypeError,
-        "is not a view on an ArrayBuffer or SharedArrayBuffer",
+        "can not be converted to sequence.",
         opts,
       );
     }
-
-    if (!opts.allowShared && isSharedArrayBuffer(V.buffer)) {
+    const iter = V?.[SymbolIterator]?.();
+    if (iter === undefined) {
       throw makeException(
         TypeError,
-        "is a view on a SharedArrayBuffer, which is not allowed",
+        "can not be converted to sequence.",
         opts,
       );
     }
-
-    return V;
-  };
-
-  converters.BufferSource = (V, opts = {}) => {
-    if (ArrayBufferIsView(V)) {
-      if (!opts.allowShared && isSharedArrayBuffer(V.buffer)) {
+    const array = [];
+    while (true) {
+      const res = iter?.next?.();
+      if (res === undefined) {
         throw makeException(
           TypeError,
-          "is a view on a SharedArrayBuffer, which is not allowed",
+          "can not be converted to sequence.",
           opts,
         );
       }
-
-      return V;
+      if (res.done === true) break;
+      const val = converter(res.value, {
+        ...opts,
+        context: `${opts.context}, index ${array.length}`,
+      });
+      ArrayPrototypePush(array, val);
     }
+    return array;
+  };
+}
 
-    if (!opts.allowShared && !isNonSharedArrayBuffer(V)) {
-      throw makeException(
-        TypeError,
-        "is not an ArrayBuffer or a view on one",
-        opts,
-      );
-    }
-    if (
-      opts.allowShared &&
-      !isSharedArrayBuffer(V) &&
-      !isNonSharedArrayBuffer(V)
-    ) {
+function createRecordConverter(keyConverter, valueConverter) {
+  return (V, opts) => {
+    if (type(V) !== "Object") {
       throw makeException(
         TypeError,
-        "is not an ArrayBuffer, SharedArrayBuffer, or a view on one",
+        "can not be converted to dictionary.",
         opts,
       );
     }
-
-    return V;
-  };
-
-  converters.DOMTimeStamp = converters["unsigned long long"];
-  converters.DOMHighResTimeStamp = converters["double"];
-
-  converters.Function = convertCallbackFunction;
-
-  converters.VoidFunction = convertCallbackFunction;
-
-  converters["UVString?"] = createNullableConverter(
-    converters.USVString,
-  );
-  converters["sequence<double>"] = createSequenceConverter(
-    converters.double,
-  );
-  converters["sequence<object>"] = createSequenceConverter(
-    converters.object,
-  );
-  converters["Promise<undefined>"] = createPromiseConverter(() => undefined);
-
-  converters["sequence<ByteString>"] = createSequenceConverter(
-    converters.ByteString,
-  );
-  converters["sequence<sequence<ByteString>>"] = createSequenceConverter(
-    converters["sequence<ByteString>"],
-  );
-  converters["record<ByteString, ByteString>"] = createRecordConverter(
-    converters.ByteString,
-    converters.ByteString,
-  );
-
-  converters["sequence<USVString>"] = createSequenceConverter(
-    converters.USVString,
-  );
-  converters["sequence<sequence<USVString>>"] = createSequenceConverter(
-    converters["sequence<USVString>"],
-  );
-  converters["record<USVString, USVString>"] = createRecordConverter(
-    converters.USVString,
-    converters.USVString,
-  );
-
-  converters["sequence<DOMString>"] = createSequenceConverter(
-    converters.DOMString,
-  );
-
-  function requiredArguments(length, required, opts = {}) {
-    if (length < required) {
-      const errMsg = `${
-        opts.prefix ? opts.prefix + ": " : ""
-      }${required} argument${
-        required === 1 ? "" : "s"
-      } required, but only ${length} present.`;
-      throw new TypeError(errMsg);
-    }
-  }
-
-  function createDictionaryConverter(name, ...dictionaries) {
-    let hasRequiredKey = false;
-    const allMembers = [];
-    for (let i = 0; i < dictionaries.length; ++i) {
-      const members = dictionaries[i];
-      for (let j = 0; j < members.length; ++j) {
-        const member = members[j];
-        if (member.required) {
-          hasRequiredKey = true;
+    const result = {};
+    // Fast path for common case (not a Proxy)
+    if (!core.isProxy(V)) {
+      for (const key in V) {
+        if (!ObjectPrototypeHasOwnProperty(V, key)) {
+          continue;
         }
-        ArrayPrototypePush(allMembers, member);
+        const typedKey = keyConverter(key, opts);
+        const value = V[key];
+        const typedValue = valueConverter(value, opts);
+        result[typedKey] = typedValue;
       }
+      return result;
     }
-    ArrayPrototypeSort(allMembers, (a, b) => {
-      if (a.key == b.key) {
-        return 0;
+    // Slow path if Proxy (e.g: in WPT tests)
+    const keys = ReflectOwnKeys(V);
+    for (let i = 0; i < keys.length; ++i) {
+      const key = keys[i];
+      const desc = ObjectGetOwnPropertyDescriptor(V, key);
+      if (desc !== undefined && desc.enumerable === true) {
+        const typedKey = keyConverter(key, opts);
+        const value = V[key];
+        const typedValue = valueConverter(value, opts);
+        result[typedKey] = typedValue;
       }
-      return a.key < b.key ? -1 : 1;
+    }
+    return result;
+  };
+}
+
+function createPromiseConverter(converter) {
+  return (V, opts) =>
+    PromisePrototypeThen(PromiseResolve(V), (V) => converter(V, opts));
+}
+
+function invokeCallbackFunction(
+  callable,
+  args,
+  thisArg,
+  returnValueConverter,
+  opts,
+) {
+  try {
+    const rv = ReflectApply(callable, thisArg, args);
+    return returnValueConverter(rv, {
+      prefix: opts.prefix,
+      context: "return value",
     });
-
-    const defaultValues = {};
-    for (let i = 0; i < allMembers.length; ++i) {
-      const member = allMembers[i];
-      if (ReflectHas(member, "defaultValue")) {
-        const idlMemberValue = member.defaultValue;
-        const imvType = typeof idlMemberValue;
-        // Copy by value types can be directly assigned, copy by reference types
-        // need to be re-created for each allocation.
-        if (
-          imvType === "number" || imvType === "boolean" ||
-          imvType === "string" || imvType === "bigint" ||
-          imvType === "undefined"
-        ) {
-          defaultValues[member.key] = member.converter(idlMemberValue, {});
-        } else {
-          ObjectDefineProperty(defaultValues, member.key, {
-            get() {
-              return member.converter(idlMemberValue, member.defaultValue);
-            },
-            enumerable: true,
-          });
-        }
-      }
+  } catch (err) {
+    if (opts.returnsPromise === true) {
+      return PromiseReject(err);
     }
+    throw err;
+  }
+}
 
-    return function (V, opts = {}) {
-      const typeV = type(V);
-      switch (typeV) {
-        case "Undefined":
-        case "Null":
-        case "Object":
-          break;
-        default:
-          throw makeException(
-            TypeError,
-            "can not be converted to a dictionary",
-            opts,
-          );
-      }
-      const esDict = V;
-
-      const idlDict = ObjectAssign({}, defaultValues);
-
-      // NOTE: fast path Null and Undefined.
-      if ((V === undefined || V === null) && !hasRequiredKey) {
-        return idlDict;
-      }
-
-      for (let i = 0; i < allMembers.length; ++i) {
-        const member = allMembers[i];
-        const key = member.key;
-
-        let esMemberValue;
-        if (typeV === "Undefined" || typeV === "Null") {
-          esMemberValue = undefined;
-        } else {
-          esMemberValue = esDict[key];
-        }
-
-        if (esMemberValue !== undefined) {
-          const context = `'${key}' of '${name}'${
-            opts.context ? ` (${opts.context})` : ""
-          }`;
-          const converter = member.converter;
-          const idlMemberValue = converter(esMemberValue, { ...opts, context });
-          idlDict[key] = idlMemberValue;
-        } else if (member.required) {
-          throw makeException(
-            TypeError,
-            `can not be converted to '${name}' because '${key}' is required in '${name}'.`,
-            opts,
-          );
-        }
-      }
+const brand = Symbol("[[webidl.brand]]");
 
-      return idlDict;
-    };
+function createInterfaceConverter(name, prototype) {
+  return (V, opts) => {
+    if (!ObjectPrototypeIsPrototypeOf(prototype, V) || V[brand] !== brand) {
+      throw makeException(TypeError, `is not of type ${name}.`, opts);
+    }
+    return V;
+  };
+}
+
+// TODO(lucacasonato): have the user pass in the prototype, and not the type.
+function createBranded(Type) {
+  const t = ObjectCreate(Type.prototype);
+  t[brand] = brand;
+  return t;
+}
+
+function assertBranded(self, prototype) {
+  if (
+    !ObjectPrototypeIsPrototypeOf(prototype, self) || self[brand] !== brand
+  ) {
+    throw new TypeError("Illegal invocation");
+  }
+}
+
+function illegalConstructor() {
+  throw new TypeError("Illegal constructor");
+}
+
+function define(target, source) {
+  const keys = ReflectOwnKeys(source);
+  for (let i = 0; i < keys.length; ++i) {
+    const key = keys[i];
+    const descriptor = ReflectGetOwnPropertyDescriptor(source, key);
+    if (descriptor && !ReflectDefineProperty(target, key, descriptor)) {
+      throw new TypeError(`Cannot redefine property: ${String(key)}`);
+    }
   }
+}
 
-  // https://heycam.github.io/webidl/#es-enumeration
-  function createEnumConverter(name, values) {
-    const E = new Set(values);
+const _iteratorInternal = Symbol("iterator internal");
 
-    return function (V, opts = {}) {
-      const S = String(V);
+const globalIteratorPrototype = ObjectGetPrototypeOf(ArrayIteratorPrototype);
 
-      if (!E.has(S)) {
+function mixinPairIterable(name, prototype, dataSymbol, keyKey, valueKey) {
+  const iteratorPrototype = ObjectCreate(globalIteratorPrototype, {
+    [SymbolToStringTag]: { configurable: true, value: `${name} Iterator` },
+  });
+  define(iteratorPrototype, {
+    next() {
+      const internal = this && this[_iteratorInternal];
+      if (!internal) {
         throw new TypeError(
-          `${
-            opts.prefix ? opts.prefix + ": " : ""
-          }The provided value '${S}' is not a valid enum value of type ${name}.`,
+          `next() called on a value that is not a ${name} iterator object`,
         );
       }
-
-      return S;
-    };
+      const { target, kind, index } = internal;
+      const values = target[dataSymbol];
+      const len = values.length;
+      if (index >= len) {
+        return { value: undefined, done: true };
+      }
+      const pair = values[index];
+      internal.index = index + 1;
+      let result;
+      switch (kind) {
+        case "key":
+          result = pair[keyKey];
+          break;
+        case "value":
+          result = pair[valueKey];
+          break;
+        case "key+value":
+          result = [pair[keyKey], pair[valueKey]];
+          break;
+      }
+      return { value: result, done: false };
+    },
+  });
+  function createDefaultIterator(target, kind) {
+    const iterator = ObjectCreate(iteratorPrototype);
+    ObjectDefineProperty(iterator, _iteratorInternal, {
+      value: { target, kind, index: 0 },
+      configurable: true,
+    });
+    return iterator;
   }
 
-  function createNullableConverter(converter) {
-    return (V, opts = {}) => {
-      // FIXME: If Type(V) is not Object, and the conversion to an IDL value is
-      // being performed due to V being assigned to an attribute whose type is a
-      // nullable callback function that is annotated with
-      // [LegacyTreatNonObjectAsNull], then return the IDL nullable type T?
-      // value null.
-
-      if (V === null || V === undefined) return null;
-      return converter(V, opts);
-    };
+  function entries() {
+    assertBranded(this, prototype.prototype);
+    return createDefaultIterator(this, "key+value");
   }
 
-  // https://heycam.github.io/webidl/#es-sequence
-  function createSequenceConverter(converter) {
-    return function (V, opts = {}) {
-      if (type(V) !== "Object") {
-        throw makeException(
-          TypeError,
-          "can not be converted to sequence.",
-          opts,
-        );
-      }
-      const iter = V?.[SymbolIterator]?.();
-      if (iter === undefined) {
-        throw makeException(
-          TypeError,
-          "can not be converted to sequence.",
-          opts,
-        );
-      }
-      const array = [];
-      while (true) {
-        const res = iter?.next?.();
-        if (res === undefined) {
-          throw makeException(
-            TypeError,
-            "can not be converted to sequence.",
-            opts,
-          );
-        }
-        if (res.done === true) break;
-        const val = converter(res.value, {
-          ...opts,
-          context: `${opts.context}, index ${array.length}`,
+  const properties = {
+    entries: {
+      value: entries,
+      writable: true,
+      enumerable: true,
+      configurable: true,
+    },
+    [SymbolIterator]: {
+      value: entries,
+      writable: true,
+      enumerable: false,
+      configurable: true,
+    },
+    keys: {
+      value: function keys() {
+        assertBranded(this, prototype.prototype);
+        return createDefaultIterator(this, "key");
+      },
+      writable: true,
+      enumerable: true,
+      configurable: true,
+    },
+    values: {
+      value: function values() {
+        assertBranded(this, prototype.prototype);
+        return createDefaultIterator(this, "value");
+      },
+      writable: true,
+      enumerable: true,
+      configurable: true,
+    },
+    forEach: {
+      value: function forEach(idlCallback, thisArg = undefined) {
+        assertBranded(this, prototype.prototype);
+        const prefix = `Failed to execute 'forEach' on '${name}'`;
+        requiredArguments(arguments.length, 1, { prefix });
+        idlCallback = converters["Function"](idlCallback, {
+          prefix,
+          context: "Argument 1",
         });
-        ArrayPrototypePush(array, val);
-      }
-      return array;
-    };
-  }
-
-  function createRecordConverter(keyConverter, valueConverter) {
-    return (V, opts) => {
-      if (type(V) !== "Object") {
-        throw makeException(
-          TypeError,
-          "can not be converted to dictionary.",
-          opts,
+        idlCallback = FunctionPrototypeBind(
+          idlCallback,
+          thisArg ?? globalThis,
         );
-      }
-      const result = {};
-      // Fast path for common case (not a Proxy)
-      if (!core.isProxy(V)) {
-        for (const key in V) {
-          if (!ObjectPrototypeHasOwnProperty(V, key)) {
-            continue;
-          }
-          const typedKey = keyConverter(key, opts);
-          const value = V[key];
-          const typedValue = valueConverter(value, opts);
-          result[typedKey] = typedValue;
+        const pairs = this[dataSymbol];
+        for (let i = 0; i < pairs.length; i++) {
+          const entry = pairs[i];
+          idlCallback(entry[valueKey], entry[keyKey], this);
         }
-        return result;
-      }
-      // Slow path if Proxy (e.g: in WPT tests)
-      const keys = ReflectOwnKeys(V);
-      for (let i = 0; i < keys.length; ++i) {
-        const key = keys[i];
-        const desc = ObjectGetOwnPropertyDescriptor(V, key);
-        if (desc !== undefined && desc.enumerable === true) {
-          const typedKey = keyConverter(key, opts);
-          const value = V[key];
-          const typedValue = valueConverter(value, opts);
-          result[typedKey] = typedValue;
-        }
-      }
-      return result;
-    };
-  }
-
-  function createPromiseConverter(converter) {
-    return (V, opts) =>
-      PromisePrototypeThen(PromiseResolve(V), (V) => converter(V, opts));
-  }
-
-  function invokeCallbackFunction(
-    callable,
-    args,
-    thisArg,
-    returnValueConverter,
-    opts,
-  ) {
-    try {
-      const rv = ReflectApply(callable, thisArg, args);
-      return returnValueConverter(rv, {
-        prefix: opts.prefix,
-        context: "return value",
-      });
-    } catch (err) {
-      if (opts.returnsPromise === true) {
-        return PromiseReject(err);
-      }
-      throw err;
+      },
+      writable: true,
+      enumerable: true,
+      configurable: true,
+    },
+  };
+  return ObjectDefineProperties(prototype.prototype, properties);
+}
+
+function configurePrototype(prototype) {
+  const descriptors = ObjectGetOwnPropertyDescriptors(prototype.prototype);
+  for (const key in descriptors) {
+    if (!ObjectPrototypeHasOwnProperty(descriptors, key)) {
+      continue;
     }
-  }
-
-  const brand = Symbol("[[webidl.brand]]");
-
-  function createInterfaceConverter(name, prototype) {
-    return (V, opts) => {
-      if (!ObjectPrototypeIsPrototypeOf(prototype, V) || V[brand] !== brand) {
-        throw makeException(TypeError, `is not of type ${name}.`, opts);
-      }
-      return V;
-    };
-  }
-
-  // TODO(lucacasonato): have the user pass in the prototype, and not the type.
-  function createBranded(Type) {
-    const t = ObjectCreate(Type.prototype);
-    t[brand] = brand;
-    return t;
-  }
-
-  function assertBranded(self, prototype) {
+    if (key === "constructor") continue;
+    const descriptor = descriptors[key];
     if (
-      !ObjectPrototypeIsPrototypeOf(prototype, self) || self[brand] !== brand
+      ReflectHas(descriptor, "value") &&
+      typeof descriptor.value === "function"
     ) {
-      throw new TypeError("Illegal invocation");
-    }
-  }
-
-  function illegalConstructor() {
-    throw new TypeError("Illegal constructor");
-  }
-
-  function define(target, source) {
-    const keys = ReflectOwnKeys(source);
-    for (let i = 0; i < keys.length; ++i) {
-      const key = keys[i];
-      const descriptor = ReflectGetOwnPropertyDescriptor(source, key);
-      if (descriptor && !ReflectDefineProperty(target, key, descriptor)) {
-        throw new TypeError(`Cannot redefine property: ${String(key)}`);
-      }
-    }
-  }
-
-  const _iteratorInternal = Symbol("iterator internal");
-
-  const globalIteratorPrototype = ObjectGetPrototypeOf(ArrayIteratorPrototype);
-
-  function mixinPairIterable(name, prototype, dataSymbol, keyKey, valueKey) {
-    const iteratorPrototype = ObjectCreate(globalIteratorPrototype, {
-      [SymbolToStringTag]: { configurable: true, value: `${name} Iterator` },
-    });
-    define(iteratorPrototype, {
-      next() {
-        const internal = this && this[_iteratorInternal];
-        if (!internal) {
-          throw new TypeError(
-            `next() called on a value that is not a ${name} iterator object`,
-          );
-        }
-        const { target, kind, index } = internal;
-        const values = target[dataSymbol];
-        const len = values.length;
-        if (index >= len) {
-          return { value: undefined, done: true };
-        }
-        const pair = values[index];
-        internal.index = index + 1;
-        let result;
-        switch (kind) {
-          case "key":
-            result = pair[keyKey];
-            break;
-          case "value":
-            result = pair[valueKey];
-            break;
-          case "key+value":
-            result = [pair[keyKey], pair[valueKey]];
-            break;
-        }
-        return { value: result, done: false };
-      },
-    });
-    function createDefaultIterator(target, kind) {
-      const iterator = ObjectCreate(iteratorPrototype);
-      ObjectDefineProperty(iterator, _iteratorInternal, {
-        value: { target, kind, index: 0 },
+      ObjectDefineProperty(prototype.prototype, key, {
+        enumerable: true,
+        writable: true,
+        configurable: true,
+      });
+    } else if (ReflectHas(descriptor, "get")) {
+      ObjectDefineProperty(prototype.prototype, key, {
+        enumerable: true,
         configurable: true,
       });
-      return iterator;
     }
+  }
+  ObjectDefineProperty(prototype.prototype, SymbolToStringTag, {
+    value: prototype.name,
+    enumerable: false,
+    configurable: true,
+    writable: false,
+  });
+}
 
-    function entries() {
-      assertBranded(this, prototype.prototype);
-      return createDefaultIterator(this, "key+value");
-    }
+const setlikeInner = Symbol("[[set]]");
 
-    const properties = {
-      entries: {
-        value: entries,
-        writable: true,
-        enumerable: true,
-        configurable: true,
+// Ref: https://webidl.spec.whatwg.org/#es-setlike
+function setlike(obj, objPrototype, readonly) {
+  ObjectDefineProperties(obj, {
+    size: {
+      configurable: true,
+      enumerable: true,
+      get() {
+        assertBranded(this, objPrototype);
+        return obj[setlikeInner].size;
       },
-      [SymbolIterator]: {
-        value: entries,
-        writable: true,
-        enumerable: false,
-        configurable: true,
+    },
+    [SymbolIterator]: {
+      configurable: true,
+      enumerable: false,
+      writable: true,
+      value() {
+        assertBranded(this, objPrototype);
+        return obj[setlikeInner][SymbolIterator]();
       },
-      keys: {
-        value: function keys() {
-          assertBranded(this, prototype.prototype);
-          return createDefaultIterator(this, "key");
-        },
-        writable: true,
-        enumerable: true,
-        configurable: true,
+    },
+    entries: {
+      configurable: true,
+      enumerable: true,
+      writable: true,
+      value() {
+        assertBranded(this, objPrototype);
+        return SetPrototypeEntries(obj[setlikeInner]);
       },
-      values: {
-        value: function values() {
-          assertBranded(this, prototype.prototype);
-          return createDefaultIterator(this, "value");
-        },
-        writable: true,
-        enumerable: true,
-        configurable: true,
+    },
+    keys: {
+      configurable: true,
+      enumerable: true,
+      writable: true,
+      value() {
+        assertBranded(this, objPrototype);
+        return SetPrototypeKeys(obj[setlikeInner]);
       },
-      forEach: {
-        value: function forEach(idlCallback, thisArg = undefined) {
-          assertBranded(this, prototype.prototype);
-          const prefix = `Failed to execute 'forEach' on '${name}'`;
-          requiredArguments(arguments.length, 1, { prefix });
-          idlCallback = converters["Function"](idlCallback, {
-            prefix,
-            context: "Argument 1",
-          });
-          idlCallback = FunctionPrototypeBind(
-            idlCallback,
-            thisArg ?? globalThis,
-          );
-          const pairs = this[dataSymbol];
-          for (let i = 0; i < pairs.length; i++) {
-            const entry = pairs[i];
-            idlCallback(entry[valueKey], entry[keyKey], this);
-          }
-        },
-        writable: true,
-        enumerable: true,
-        configurable: true,
+    },
+    values: {
+      configurable: true,
+      enumerable: true,
+      writable: true,
+      value() {
+        assertBranded(this, objPrototype);
+        return SetPrototypeValues(obj[setlikeInner]);
       },
-    };
-    return ObjectDefineProperties(prototype.prototype, properties);
-  }
-
-  function configurePrototype(prototype) {
-    const descriptors = ObjectGetOwnPropertyDescriptors(prototype.prototype);
-    for (const key in descriptors) {
-      if (!ObjectPrototypeHasOwnProperty(descriptors, key)) {
-        continue;
-      }
-      if (key === "constructor") continue;
-      const descriptor = descriptors[key];
-      if (
-        ReflectHas(descriptor, "value") &&
-        typeof descriptor.value === "function"
-      ) {
-        ObjectDefineProperty(prototype.prototype, key, {
-          enumerable: true,
-          writable: true,
-          configurable: true,
-        });
-      } else if (ReflectHas(descriptor, "get")) {
-        ObjectDefineProperty(prototype.prototype, key, {
-          enumerable: true,
-          configurable: true,
-        });
-      }
-    }
-    ObjectDefineProperty(prototype.prototype, SymbolToStringTag, {
-      value: prototype.name,
-      enumerable: false,
+    },
+    forEach: {
       configurable: true,
-      writable: false,
-    });
-  }
-
-  const setlikeInner = Symbol("[[set]]");
-
-  // Ref: https://webidl.spec.whatwg.org/#es-setlike
-  function setlike(obj, objPrototype, readonly) {
-    ObjectDefineProperties(obj, {
-      size: {
-        configurable: true,
-        enumerable: true,
-        get() {
-          assertBranded(this, objPrototype);
-          return obj[setlikeInner].size;
-        },
+      enumerable: true,
+      writable: true,
+      value(callbackfn, thisArg) {
+        assertBranded(this, objPrototype);
+        return SetPrototypeForEach(obj[setlikeInner], callbackfn, thisArg);
       },
-      [SymbolIterator]: {
-        configurable: true,
-        enumerable: false,
-        writable: true,
-        value() {
-          assertBranded(this, objPrototype);
-          return obj[setlikeInner][SymbolIterator]();
-        },
+    },
+    has: {
+      configurable: true,
+      enumerable: true,
+      writable: true,
+      value(value) {
+        assertBranded(this, objPrototype);
+        return SetPrototypeHas(obj[setlikeInner], value);
       },
-      entries: {
+    },
+  });
+
+  if (!readonly) {
+    ObjectDefineProperties(obj, {
+      add: {
         configurable: true,
         enumerable: true,
         writable: true,
-        value() {
+        value(value) {
           assertBranded(this, objPrototype);
-          return SetPrototypeEntries(obj[setlikeInner]);
+          return SetPrototypeAdd(obj[setlikeInner], value);
         },
       },
-      keys: {
+      delete: {
         configurable: true,
         enumerable: true,
         writable: true,
-        value() {
+        value(value) {
           assertBranded(this, objPrototype);
-          return SetPrototypeKeys(obj[setlikeInner]);
+          return SetPrototypeDelete(obj[setlikeInner], value);
         },
       },
-      values: {
+      clear: {
         configurable: true,
         enumerable: true,
         writable: true,
         value() {
           assertBranded(this, objPrototype);
-          return SetPrototypeValues(obj[setlikeInner]);
-        },
-      },
-      forEach: {
-        configurable: true,
-        enumerable: true,
-        writable: true,
-        value(callbackfn, thisArg) {
-          assertBranded(this, objPrototype);
-          return SetPrototypeForEach(obj[setlikeInner], callbackfn, thisArg);
-        },
-      },
-      has: {
-        configurable: true,
-        enumerable: true,
-        writable: true,
-        value(value) {
-          assertBranded(this, objPrototype);
-          return SetPrototypeHas(obj[setlikeInner], value);
+          return SetPrototypeClear(obj[setlikeInner]);
         },
       },
     });
-
-    if (!readonly) {
-      ObjectDefineProperties(obj, {
-        add: {
-          configurable: true,
-          enumerable: true,
-          writable: true,
-          value(value) {
-            assertBranded(this, objPrototype);
-            return SetPrototypeAdd(obj[setlikeInner], value);
-          },
-        },
-        delete: {
-          configurable: true,
-          enumerable: true,
-          writable: true,
-          value(value) {
-            assertBranded(this, objPrototype);
-            return SetPrototypeDelete(obj[setlikeInner], value);
-          },
-        },
-        clear: {
-          configurable: true,
-          enumerable: true,
-          writable: true,
-          value() {
-            assertBranded(this, objPrototype);
-            return SetPrototypeClear(obj[setlikeInner]);
-          },
-        },
-      });
-    }
   }
-
-  window.__bootstrap ??= {};
-  window.__bootstrap.webidl = {
-    type,
-    makeException,
-    converters,
-    requiredArguments,
-    createDictionaryConverter,
-    createEnumConverter,
-    createNullableConverter,
-    createSequenceConverter,
-    createRecordConverter,
-    createPromiseConverter,
-    invokeCallbackFunction,
-    createInterfaceConverter,
-    brand,
-    createBranded,
-    assertBranded,
-    illegalConstructor,
-    mixinPairIterable,
-    configurePrototype,
-    setlike,
-    setlikeInner,
-  };
-})(this);
+}
+
+export {
+  assertBranded,
+  brand,
+  configurePrototype,
+  converters,
+  createBranded,
+  createDictionaryConverter,
+  createEnumConverter,
+  createInterfaceConverter,
+  createNullableConverter,
+  createPromiseConverter,
+  createRecordConverter,
+  createSequenceConverter,
+  illegalConstructor,
+  invokeCallbackFunction,
+  makeException,
+  mixinPairIterable,
+  requiredArguments,
+  setlike,
+  setlikeInner,
+  type,
+};