[torque] introduce JSAny type for user-accessible JavaScript values

This CL introduces a JSAny type for user-exposed JavaScript values and
a few new types to define it. Especially, it splits Symbol into
PrivateSymbol (not exposed) and PublicSymbol (JavaScript exposed
symbols).

The change is mostly mechanical, but a few things are interesting:
- PropertyKey and JSPrimitive were designed to coincide with the spec
  notions of IsPropertyKey() and primitive value, respectively.
- Since Name is an open type, we define AnyName to be the known
  subtypes of Name. This is not too elegant, but by using AnyName
  instead of Name, typeswitch can properly conclude something if a
  subtype of Name is excluded.

Small drive-by changes, which were necessary:
- Allow subtyping on label parameters.
- Fix the formatting of typeswitch, it was broken with union types
  in case types.

Bug: v8:7793
Change-Id: I14b10507f8cf316ad85e048fe8d53d1df5e0bb13
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1735322
Commit-Queue: Tobias Tebbi <tebbi@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#63114}

src/builtins/arguments.tq

@@ -8,7 +8,7 @@ struct Arguments {
   const length: intptr;
 }
 
-extern operator '[]' macro GetArgumentValue(Arguments, intptr): Object;
+extern operator '[]' macro GetArgumentValue(Arguments, intptr): JSAny;
 
 extern macro GetFrameArguments(FrameWithArguments, intptr): Arguments;
 

src/builtins/array-copywithin.tq

@@ -9,7 +9,7 @@ namespace array_copywithin {
 
   // https://tc39.github.io/ecma262/#sec-array.prototype.copyWithin
   transitioning javascript builtin ArrayPrototypeCopyWithin(
-      js-implicit context: Context, receiver: Object)(...arguments): Object {
+      js-implicit context: Context, receiver: JSAny)(...arguments): JSAny {
     // 1. Let O be ? ToObject(this value).
     const object: JSReceiver = ToObject_Inline(context, receiver);
 
@@ -68,7 +68,7 @@ namespace array_copywithin {
       // d. If fromPresent is true, then.
       if (fromPresent == True) {
         // i. Let fromVal be ? Get(O, fromKey).
-        const fromVal: Object = GetProperty(object, from);
+        const fromVal: JSAny = GetProperty(object, from);
 
         // ii. Perform ? Set(O, toKey, fromVal, true).
         SetProperty(object, to, fromVal);

src/builtins/array-every.tq

@@ -5,15 +5,14 @@
 namespace array {
   transitioning javascript builtin
   ArrayEveryLoopEagerDeoptContinuation(
-      js-implicit context: Context, receiver: Object)(
-      callback: Object, thisArg: Object, initialK: Object,
-      length: Object): Object {
+      js-implicit context: Context, receiver: JSAny)(
+      callback: JSAny, thisArg: JSAny, initialK: JSAny, length: JSAny): JSAny {
     // All continuation points in the optimized every implementation are
     // after the ToObject(O) call that ensures we are dealing with a
     // JSReceiver.
     //
     // Also, this great mass of casts is necessary because the signature
-    // of Torque javascript builtins requires Object type for all parameters
+    // of Torque javascript builtins requires JSAny type for all parameters
     // other than {context}.
     const jsreceiver = Cast<JSReceiver>(receiver) otherwise unreachable;
     const callbackfn = Cast<Callable>(callback) otherwise unreachable;
@@ -27,9 +26,9 @@ namespace array {
 
   transitioning javascript builtin
   ArrayEveryLoopLazyDeoptContinuation(
-      js-implicit context: Context, receiver: Object)(
-      callback: Object, thisArg: Object, initialK: Object, length: Object,
-      result: Object): Object {
+      js-implicit context: Context, receiver: JSAny)(
+      callback: JSAny, thisArg: JSAny, initialK: JSAny, length: JSAny,
+      result: JSAny): JSAny {
     // All continuation points in the optimized every implementation are
     // after the ToObject(O) call that ensures we are dealing with a
     // JSReceiver.
@@ -53,9 +52,9 @@ namespace array {
   }
 
   transitioning builtin ArrayEveryLoopContinuation(implicit context: Context)(
-      _receiver: JSReceiver, callbackfn: Callable, thisArg: Object,
-      _array: Object, o: JSReceiver, initialK: Number, length: Number,
-      _initialTo: Object): Object {
+      _receiver: JSReceiver, callbackfn: Callable, thisArg: JSAny,
+      _array: JSAny, o: JSReceiver, initialK: Number, length: Number,
+      _initialTo: JSAny): JSAny {
     // 5. Let k be 0.
     // 6. Repeat, while k < len
     for (let k: Number = initialK; k < length; k++) {
@@ -69,10 +68,10 @@ namespace array {
       // 6c. If kPresent is true, then
       if (kPresent == True) {
         // 6c. i. Let kValue be ? Get(O, Pk).
-        const kValue: Object = GetProperty(o, k);
+        const kValue: JSAny = GetProperty(o, k);
 
         // 6c. ii. Perform ? Call(callbackfn, T, <kValue, k, O>).
-        const result: Object = Call(context, callbackfn, thisArg, kValue, k, o);
+        const result: JSAny = Call(context, callbackfn, thisArg, kValue, k, o);
 
         // iii. If selected is true, then...
         if (!ToBoolean(result)) {
@@ -86,7 +85,7 @@ namespace array {
   }
 
   transitioning macro FastArrayEvery(implicit context: Context)(
-      o: JSReceiver, len: Number, callbackfn: Callable, thisArg: Object): Object
+      o: JSReceiver, len: Number, callbackfn: Callable, thisArg: JSAny): JSAny
       labels Bailout(Smi) {
     let k: Smi = 0;
     const smiLen = Cast<Smi>(len) otherwise goto Bailout(k);
@@ -99,8 +98,8 @@ namespace array {
 
       // Ensure that we haven't walked beyond a possibly updated length.
       if (k >= fastOW.Get().length) goto Bailout(k);
-      const value: Object = fastOW.LoadElementNoHole(k) otherwise continue;
-      const result: Object =
+      const value: JSAny = fastOW.LoadElementNoHole(k) otherwise continue;
+      const result: JSAny =
           Call(context, callbackfn, thisArg, value, k, fastOW.Get());
       if (!ToBoolean(result)) {
         return False;
@@ -111,8 +110,8 @@ namespace array {
 
   // https://tc39.github.io/ecma262/#sec-array.prototype.every
   transitioning javascript builtin
-  ArrayEvery(js-implicit context: Context, receiver: Object)(...arguments):
-      Object {
+  ArrayEvery(js-implicit context: Context, receiver: JSAny)(...arguments):
+      JSAny {
     try {
       RequireObjectCoercible(receiver, 'Array.prototype.every');
 
@@ -129,7 +128,7 @@ namespace array {
       const callbackfn = Cast<Callable>(arguments[0]) otherwise TypeError;
 
       // 4. If thisArg is present, let T be thisArg; else let T be undefined.
-      const thisArg: Object = arguments.length > 1 ? arguments[1] : Undefined;
+      const thisArg: JSAny = arguments.length > 1 ? arguments[1] : Undefined;
 
       // Special cases.
       try {

src/builtins/array-filter.tq

@@ -5,15 +5,15 @@
 namespace array_filter {
   transitioning javascript builtin
   ArrayFilterLoopEagerDeoptContinuation(
-      js-implicit context: Context, receiver: Object)(
-      callback: Object, thisArg: Object, array: Object, initialK: Object,
-      length: Object, initialTo: Object): Object {
+      js-implicit context: Context, receiver: JSAny)(
+      callback: JSAny, thisArg: JSAny, array: JSAny, initialK: JSAny,
+      length: JSAny, initialTo: JSAny): JSAny {
     // All continuation points in the optimized filter implementation are
     // after the ToObject(O) call that ensures we are dealing with a
     // JSReceiver.
     //
     // Also, this great mass of casts is necessary because the signature
-    // of Torque javascript builtins requires Object type for all parameters
+    // of Torque javascript builtins requires JSAny type for all parameters
     // other than {context}.
     const jsreceiver = Cast<JSReceiver>(receiver) otherwise unreachable;
     const callbackfn = Cast<Callable>(callback) otherwise unreachable;
@@ -29,10 +29,9 @@ namespace array_filter {
 
   transitioning javascript builtin
   ArrayFilterLoopLazyDeoptContinuation(
-      js-implicit context: Context, receiver: Object)(
-      callback: Object, thisArg: Object, array: Object, initialK: Object,
-      length: Object, valueK: Object, initialTo: Object,
-      result: Object): Object {
+      js-implicit context: Context, receiver: JSAny)(
+      callback: JSAny, thisArg: JSAny, array: JSAny, initialK: JSAny,
+      length: JSAny, valueK: JSAny, initialTo: JSAny, result: JSAny): JSAny {
     // All continuation points in the optimized filter implementation are
     // after the ToObject(O) call that ensures we are dealing with a
     // JSReceiver.
@@ -60,9 +59,9 @@ namespace array_filter {
   }
 
   transitioning builtin ArrayFilterLoopContinuation(implicit context: Context)(
-      _receiver: JSReceiver, callbackfn: Callable, thisArg: Object,
+      _receiver: JSReceiver, callbackfn: Callable, thisArg: JSAny,
       array: JSReceiver, o: JSReceiver, initialK: Number, length: Number,
-      initialTo: Number): Object {
+      initialTo: Number): JSAny {
     let to: Number = initialTo;
     // 5. Let k be 0.
     // 6. Repeat, while k < len
@@ -77,10 +76,10 @@ namespace array_filter {
       // 6c. If kPresent is true, then
       if (kPresent == True) {
         // 6c. i. Let kValue be ? Get(O, Pk).
-        const kValue: Object = GetProperty(o, k);
+        const kValue: JSAny = GetProperty(o, k);
 
         // 6c. ii. Perform ? Call(callbackfn, T, <kValue, k, O>).
-        const result: Object = Call(context, callbackfn, thisArg, kValue, k, o);
+        const result: JSAny = Call(context, callbackfn, thisArg, kValue, k, o);
 
         // iii. If selected is true, then...
         if (ToBoolean(result)) {
@@ -97,7 +96,7 @@ namespace array_filter {
   }
 
   transitioning macro FastArrayFilter(implicit context: Context)(
-      fastO: FastJSArray, len: Smi, callbackfn: Callable, thisArg: Object,
+      fastO: FastJSArray, len: Smi, callbackfn: Callable, thisArg: JSAny,
       output: FastJSArray) labels Bailout(Number, Number) {
     let k: Smi = 0;
     let to: Smi = 0;
@@ -112,8 +111,8 @@ namespace array_filter {
 
       // Ensure that we haven't walked beyond a possibly updated length.
       if (k >= fastOW.Get().length) goto Bailout(k, to);
-      const value: Object = fastOW.LoadElementNoHole(k) otherwise continue;
-      const result: Object =
+      const value: JSAny = fastOW.LoadElementNoHole(k) otherwise continue;
+      const result: JSAny =
           Call(context, callbackfn, thisArg, value, k, fastOW.Get());
       if (ToBoolean(result)) {
         try {
@@ -147,8 +146,8 @@ namespace array_filter {
 
   // https://tc39.github.io/ecma262/#sec-array.prototype.filter
   transitioning javascript builtin
-  ArrayFilter(js-implicit context: Context, receiver: Object)(...arguments):
-      Object {
+  ArrayFilter(js-implicit context: Context, receiver: JSAny)(...arguments):
+      JSAny {
     try {
       RequireObjectCoercible(receiver, 'Array.prototype.filter');
 
@@ -165,7 +164,7 @@ namespace array_filter {
       const callbackfn = Cast<Callable>(arguments[0]) otherwise TypeError;
 
       // 4. If thisArg is present, let T be thisArg; else let T be undefined.
-      const thisArg: Object = arguments.length > 1 ? arguments[1] : Undefined;
+      const thisArg: JSAny = arguments.length > 1 ? arguments[1] : Undefined;
       let output: JSReceiver;
 
       // Special cases.

src/builtins/array-find.tq

@@ -5,15 +5,14 @@
 namespace array_find {
   transitioning javascript builtin
   ArrayFindLoopEagerDeoptContinuation(
-      js-implicit context: Context, receiver: Object)(
-      callback: Object, thisArg: Object, initialK: Object,
-      length: Object): Object {
+      js-implicit context: Context, receiver: JSAny)(
+      callback: JSAny, thisArg: JSAny, initialK: JSAny, length: JSAny): JSAny {
     // All continuation points in the optimized find implementation are
     // after the ToObject(O) call that ensures we are dealing with a
     // JSReceiver.
     //
     // Also, this great mass of casts is necessary because the signature
-    // of Torque javascript builtins requires Object type for all parameters
+    // of Torque javascript builtins requires JSAny type for all parameters
     // other than {context}.
     const jsreceiver = Cast<JSReceiver>(receiver) otherwise unreachable;
     const callbackfn = Cast<Callable>(callback) otherwise unreachable;
@@ -26,9 +25,9 @@ namespace array_find {
 
   transitioning javascript builtin
   ArrayFindLoopLazyDeoptContinuation(
-      js-implicit context: Context, receiver: Object)(
-      _callback: Object, _thisArg: Object, _initialK: Object, _length: Object,
-      _result: Object): Object {
+      js-implicit context: Context, receiver: JSAny)(
+      _callback: JSAny, _thisArg: JSAny, _initialK: JSAny, _length: JSAny,
+      _result: JSAny): JSAny {
     // This deopt continuation point is never actually called, it just
     // exists to make stack traces correct from a ThrowTypeError if the
     // callback was found to be non-callable.
@@ -40,9 +39,9 @@ namespace array_find {
   // before iteration continues.
   transitioning javascript builtin
   ArrayFindLoopAfterCallbackLazyDeoptContinuation(
-      js-implicit context: Context, receiver: Object)(
-      callback: Object, thisArg: Object, initialK: Object, length: Object,
-      foundValue: Object, isFound: Object): Object {
+      js-implicit context: Context, receiver: JSAny)(
+      callback: JSAny, thisArg: JSAny, initialK: JSAny, length: JSAny,
+      foundValue: JSAny, isFound: JSAny): JSAny {
     // All continuation points in the optimized find implementation are
     // after the ToObject(O) call that ensures we are dealing with a
     // JSReceiver.
@@ -65,8 +64,8 @@ namespace array_find {
   }
 
   transitioning builtin ArrayFindLoopContinuation(implicit context: Context)(
-      _receiver: JSReceiver, callbackfn: Callable, thisArg: Object,
-      o: JSReceiver, initialK: Number, length: Number): Object {
+      _receiver: JSReceiver, callbackfn: Callable, thisArg: JSAny,
+      o: JSReceiver, initialK: Number, length: Number): JSAny {
     // 5. Let k be 0.
     // 6. Repeat, while k < len
     for (let k: Number = initialK; k < length; k++) {
@@ -75,12 +74,11 @@ namespace array_find {
       // side-effect free and HasProperty/GetProperty do the conversion inline.
 
       // 6b. i. Let kValue be ? Get(O, Pk).
-      const value: Object = GetProperty(o, k);
+      const value: JSAny = GetProperty(o, k);
 
       // 6c. Let testResult be ToBoolean(? Call(predicate, T, <<kValue, k,
       // O>>)).
-      const testResult: Object =
-          Call(context, callbackfn, thisArg, value, k, o);
+      const testResult: JSAny = Call(context, callbackfn, thisArg, value, k, o);
 
       // 6d. If testResult is true, return kValue.
       if (ToBoolean(testResult)) {
@@ -93,7 +91,7 @@ namespace array_find {
   }
 
   transitioning macro FastArrayFind(implicit context: Context)(
-      o: JSReceiver, len: Number, callbackfn: Callable, thisArg: Object): Object
+      o: JSReceiver, len: Number, callbackfn: Callable, thisArg: JSAny): JSAny
       labels Bailout(Smi) {
     let k: Smi = 0;
     const smiLen = Cast<Smi>(len) otherwise goto Bailout(k);
@@ -107,8 +105,8 @@ namespace array_find {
       // Ensure that we haven't walked beyond a possibly updated length.
       if (k >= fastOW.Get().length) goto Bailout(k);
 
-      const value: Object = fastOW.LoadElementOrUndefined(k);
-      const testResult: Object =
+      const value: JSAny = fastOW.LoadElementOrUndefined(k);
+      const testResult: JSAny =
           Call(context, callbackfn, thisArg, value, k, fastOW.Get());
       if (ToBoolean(testResult)) {
         return value;
@@ -119,8 +117,8 @@ namespace array_find {
 
   // https://tc39.github.io/ecma262/#sec-array.prototype.find
   transitioning javascript builtin
-  ArrayPrototypeFind(js-implicit context: Context, receiver: Object)(
-      ...arguments): Object {
+  ArrayPrototypeFind(js-implicit context: Context, receiver: JSAny)(
+      ...arguments): JSAny {
     try {
       RequireObjectCoercible(receiver, 'Array.prototype.find');
 
@@ -138,7 +136,7 @@ namespace array_find {
           Cast<Callable>(arguments[0]) otherwise NotCallableError;
 
       // 4. If thisArg is present, let T be thisArg; else let T be undefined.
-      const thisArg: Object = arguments.length > 1 ? arguments[1] : Undefined;
+      const thisArg: JSAny = arguments.length > 1 ? arguments[1] : Undefined;
 
       // Special cases.
       try {

src/builtins/array-findindex.tq

@@ -5,15 +5,14 @@
 namespace array_findindex {
   transitioning javascript builtin
   ArrayFindIndexLoopEagerDeoptContinuation(
-      js-implicit context: Context, receiver: Object)(
-      callback: Object, thisArg: Object, initialK: Object,
-      length: Object): Object {
+      js-implicit context: Context, receiver: JSAny)(
+      callback: JSAny, thisArg: JSAny, initialK: JSAny, length: JSAny): JSAny {
     // All continuation points in the optimized findIndex implementation are
     // after the ToObject(O) call that ensures we are dealing with a
     // JSReceiver.
     //
     // Also, this great mass of casts is necessary because the signature
-    // of Torque javascript builtins requires Object type for all parameters
+    // of Torque javascript builtins requires JSAny type for all parameters
     // other than {context}.
     const jsreceiver = Cast<JSReceiver>(receiver) otherwise unreachable;
     const callbackfn = Cast<Callable>(callback) otherwise unreachable;
@@ -26,9 +25,9 @@ namespace array_findindex {
 
   transitioning javascript builtin
   ArrayFindIndexLoopLazyDeoptContinuation(
-      js-implicit context: Context, receiver: Object)(
-      _callback: Object, _thisArg: Object, _initialK: Object, _length: Object,
-      _result: Object): Object {
+      js-implicit context: Context, receiver: JSAny)(
+      _callback: JSAny, _thisArg: JSAny, _initialK: JSAny, _length: JSAny,
+      _result: JSAny): JSAny {
     // This deopt continuation point is never actually called, it just
     // exists to make stack traces correct from a ThrowTypeError if the
     // callback was found to be non-callable.
@@ -40,9 +39,9 @@ namespace array_findindex {
   // before iteration continues.
   transitioning javascript builtin
   ArrayFindIndexLoopAfterCallbackLazyDeoptContinuation(
-      js-implicit context: Context, receiver: Object)(
-      callback: Object, thisArg: Object, initialK: Object, length: Object,
-      foundValue: Object, isFound: Object): Object {
+      js-implicit context: Context, receiver: JSAny)(
+      callback: JSAny, thisArg: JSAny, initialK: JSAny, length: JSAny,
+      foundValue: JSAny, isFound: JSAny): JSAny {
     // All continuation points in the optimized findIndex implementation are
     // after the ToObject(O) call that ensures we are dealing with a
     // JSReceiver.
@@ -66,7 +65,7 @@ namespace array_findindex {
 
   transitioning builtin ArrayFindIndexLoopContinuation(implicit context:
                                                            Context)(
-      _receiver: JSReceiver, callbackfn: Callable, thisArg: Object,
+      _receiver: JSReceiver, callbackfn: Callable, thisArg: JSAny,
       o: JSReceiver, initialK: Number, length: Number): Number {
     // 5. Let k be 0.
     // 6. Repeat, while k < len
@@ -76,12 +75,11 @@ namespace array_findindex {
       // side-effect free and HasProperty/GetProperty do the conversion inline.
 
       // 6b. i. Let kValue be ? Get(O, Pk).
-      const value: Object = GetProperty(o, k);
+      const value: JSAny = GetProperty(o, k);
 
       // 6c. Let testResult be ToBoolean(? Call(predicate, T, <<kValue, k,
       // O>>)).
-      const testResult: Object =
-          Call(context, callbackfn, thisArg, value, k, o);
+      const testResult: JSAny = Call(context, callbackfn, thisArg, value, k, o);
 
       // 6d. If testResult is true, return k.
       if (ToBoolean(testResult)) {
@@ -94,7 +92,7 @@ namespace array_findindex {
   }
 
   transitioning macro FastArrayFindIndex(implicit context: Context)(
-      o: JSReceiver, len: Number, callbackfn: Callable, thisArg: Object): Number
+      o: JSReceiver, len: Number, callbackfn: Callable, thisArg: JSAny): Number
       labels Bailout(Smi) {
     let k: Smi = 0;
     const smiLen = Cast<Smi>(len) otherwise goto Bailout(k);
@@ -108,8 +106,8 @@ namespace array_findindex {
       // Ensure that we haven't walked beyond a possibly updated length.
       if (k >= fastOW.Get().length) goto Bailout(k);
 
-      const value: Object = fastOW.LoadElementOrUndefined(k);
-      const testResult: Object =
+      const value: JSAny = fastOW.LoadElementOrUndefined(k);
+      const testResult: JSAny =
           Call(context, callbackfn, thisArg, value, k, fastOW.Get());
       if (ToBoolean(testResult)) {
         return k;
@@ -120,8 +118,8 @@ namespace array_findindex {
 
   // https://tc39.github.io/ecma262/#sec-array.prototype.findIndex
   transitioning javascript builtin
-  ArrayPrototypeFindIndex(js-implicit context: Context, receiver: Object)(
-      ...arguments): Object {
+  ArrayPrototypeFindIndex(js-implicit context: Context, receiver: JSAny)(
+      ...arguments): JSAny {
     try {
       RequireObjectCoercible(receiver, 'Array.prototype.findIndex');
 
@@ -139,7 +137,7 @@ namespace array_findindex {
           Cast<Callable>(arguments[0]) otherwise NotCallableError;
 
       // 4. If thisArg is present, let T be thisArg; else let T be undefined.
-      const thisArg: Object = arguments.length > 1 ? arguments[1] : Undefined;
+      const thisArg: JSAny = arguments.length > 1 ? arguments[1] : Undefined;
 
       // Special cases.
       try {

src/builtins/array-foreach.tq

@@ -5,9 +5,8 @@
 namespace array_foreach {
   transitioning javascript builtin
   ArrayForEachLoopEagerDeoptContinuation(
-      js-implicit context: Context, receiver: Object)(
-      callback: Object, thisArg: Object, initialK: Object,
-      length: Object): Object {
+      js-implicit context: Context, receiver: JSAny)(
+      callback: JSAny, thisArg: JSAny, initialK: JSAny, length: JSAny): JSAny {
     // All continuation points in the optimized forEach implemntation are
     // after the ToObject(O) call that ensures we are dealing with a
     // JSReceiver.
@@ -23,9 +22,9 @@ namespace array_foreach {
 
   transitioning javascript builtin
   ArrayForEachLoopLazyDeoptContinuation(
-      js-implicit context: Context, receiver: Object)(
-      callback: Object, thisArg: Object, initialK: Object, length: Object,
-      _result: Object): Object {
+      js-implicit context: Context, receiver: JSAny)(
+      callback: JSAny, thisArg: JSAny, initialK: JSAny, length: JSAny,
+      _result: JSAny): JSAny {
     // All continuation points in the optimized forEach implemntation are
     // after the ToObject(O) call that ensures we are dealing with a
     // JSReceiver.
@@ -40,9 +39,9 @@ namespace array_foreach {
   }
 
   transitioning builtin ArrayForEachLoopContinuation(implicit context: Context)(
-      _receiver: JSReceiver, callbackfn: Callable, thisArg: Object,
-      _array: Object, o: JSReceiver, initialK: Number, len: Number,
-      _to: Object): Object {
+      _receiver: JSReceiver, callbackfn: Callable, thisArg: JSAny,
+      _array: JSAny, o: JSReceiver, initialK: Number, len: Number,
+      _to: JSAny): JSAny {
     // variables {array} and {to} are ignored.
 
     // 5. Let k be 0.
@@ -58,7 +57,7 @@ namespace array_foreach {
       // 6c. If kPresent is true, then
       if (kPresent == True) {
         // 6c. i. Let kValue be ? Get(O, Pk).
-        const kValue: Object = GetProperty(o, k);
+        const kValue: JSAny = GetProperty(o, k);
 
         // 6c. ii. Perform ? Call(callbackfn, T, <kValue, k, O>).
         Call(context, callbackfn, thisArg, kValue, k, o);
@@ -70,7 +69,7 @@ namespace array_foreach {
   }
 
   transitioning macro FastArrayForEach(implicit context: Context)(
-      o: JSReceiver, len: Number, callbackfn: Callable, thisArg: Object): Object
+      o: JSReceiver, len: Number, callbackfn: Callable, thisArg: JSAny): JSAny
       labels Bailout(Smi) {
     let k: Smi = 0;
     const smiLen = Cast<Smi>(len) otherwise goto Bailout(k);
@@ -83,7 +82,7 @@ namespace array_foreach {
 
       // Ensure that we haven't walked beyond a possibly updated length.
       if (k >= fastOW.Get().length) goto Bailout(k);
-      const value: Object = fastOW.LoadElementNoHole(k)
+      const value: JSAny = fastOW.LoadElementNoHole(k)
           otherwise continue;
       Call(context, callbackfn, thisArg, value, k, fastOW.Get());
     }
@@ -92,8 +91,8 @@ namespace array_foreach {
 
   // https://tc39.github.io/ecma262/#sec-array.prototype.foreach
   transitioning javascript builtin
-  ArrayForEach(js-implicit context: Context, receiver: Object)(...arguments):
-      Object {
+  ArrayForEach(js-implicit context: Context, receiver: JSAny)(...arguments):
+      JSAny {
     try {
       RequireObjectCoercible(receiver, 'Array.prototype.forEach');
 
@@ -110,7 +109,7 @@ namespace array_foreach {
       const callbackfn = Cast<Callable>(arguments[0]) otherwise TypeError;
 
       // 4. If thisArg is present, let T be thisArg; else let T be undefined.
-      const thisArg: Object = arguments.length > 1 ? arguments[1] : Undefined;
+      const thisArg: JSAny = arguments.length > 1 ? arguments[1] : Undefined;
 
       // Special cases.
       let k: Number = 0;

src/builtins/array-join.tq

@@ -3,7 +3,7 @@
 // found in the LICENSE file.
 
 namespace array_join {
-  type LoadJoinElementFn = builtin(Context, JSReceiver, Number) => Object;
+  type LoadJoinElementFn = builtin(Context, JSReceiver, Number) => JSAny;
 
   // Fast C call to write a fixed array (see Buffer.fixedArray) to a single
   // string.
@@ -12,12 +12,12 @@ namespace array_join {
       FixedArray, intptr, String, String): String;
 
   transitioning builtin LoadJoinElement<T: type>(
-      context: Context, receiver: JSReceiver, k: Number): Object {
+      context: Context, receiver: JSReceiver, k: Number): JSAny {
     return GetProperty(receiver, k);
   }
 
   transitioning LoadJoinElement<array::DictionaryElements>(
-      context: Context, receiver: JSReceiver, k: Number): Object {
+      context: Context, receiver: JSReceiver, k: Number): JSAny {
     const array: JSArray = UnsafeCast<JSArray>(receiver);
     const dict: NumberDictionary = UnsafeCast<NumberDictionary>(array.elements);
     try {
@@ -33,15 +33,15 @@ namespace array_join {
   }
 
   LoadJoinElement<array::FastSmiOrObjectElements>(
-      context: Context, receiver: JSReceiver, k: Number): Object {
+      context: Context, receiver: JSReceiver, k: Number): JSAny {
     const array: JSArray = UnsafeCast<JSArray>(receiver);
     const fixedArray: FixedArray = UnsafeCast<FixedArray>(array.elements);
     const element: Object = fixedArray.objects[UnsafeCast<Smi>(k)];
-    return element == TheHole ? kEmptyString : element;
+    return element == TheHole ? kEmptyString : UnsafeCast<JSAny>(element);
   }
 
   LoadJoinElement<array::FastDoubleElements>(
-      context: Context, receiver: JSReceiver, k: Number): Object {
+      context: Context, receiver: JSReceiver, k: Number): JSAny {
     const array: JSArray = UnsafeCast<JSArray>(receiver);
     const fixedDoubleArray: FixedDoubleArray =
         UnsafeCast<FixedDoubleArray>(array.elements);
@@ -51,7 +51,7 @@ namespace array_join {
   }
 
   builtin LoadJoinTypedElement<T: type>(
-      context: Context, receiver: JSReceiver, k: Number): Object {
+      context: Context, receiver: JSReceiver, k: Number): JSAny {
     const typedArray: JSTypedArray = UnsafeCast<JSTypedArray>(receiver);
     assert(!IsDetachedBuffer(typedArray.buffer));
     return typed_array::LoadFixedTypedArrayElementAsTagged(
@@ -60,14 +60,14 @@ namespace array_join {
   }
 
   transitioning builtin ConvertToLocaleString(
-      context: Context, element: Object, locales: Object,
-      options: Object): String {
+      context: Context, element: JSAny, locales: JSAny,
+      options: JSAny): String {
     if (IsNullOrUndefined(element)) return kEmptyString;
 
-    const prop: Object = GetProperty(element, 'toLocaleString');
+    const prop: JSAny = GetProperty(element, 'toLocaleString');
     try {
       const callable: Callable = Cast<Callable>(prop) otherwise TypeError;
-      let result: Object;
+      let result: JSAny;
       if (IsNullOrUndefined(locales)) {
         result = Call(context, callable, element);
       } else if (IsNullOrUndefined(options)) {
@@ -257,7 +257,7 @@ namespace array_join {
 
   transitioning macro ArrayJoinImpl<T: type>(implicit context: Context)(
       receiver: JSReceiver, sep: String, lengthNumber: Number,
-      useToLocaleString: constexpr bool, locales: Object, options: Object,
+      useToLocaleString: constexpr bool, locales: JSAny, options: JSAny,
       initialLoadFn: LoadJoinElementFn): String {
     const initialMap: Map = receiver.map;
     const len: uintptr = Convert<uintptr>(lengthNumber);
@@ -283,7 +283,7 @@ namespace array_join {
       }
 
       // b. Let element be ? Get(O, ! ToString(k)).
-      const element: Object = loadFn(context, receiver, Convert<Number>(k++));
+      const element: JSAny = loadFn(context, receiver, Convert<Number>(k++));
 
       // c. If element is undefined or null, let next be the empty String;
       //    otherwise, let next be ? ToString(element).
@@ -300,7 +300,7 @@ namespace array_join {
           case (num: Number): {
             next = NumberToString(num);
           }
-          case (obj: HeapObject): {
+          case (obj: JSAny): {
             if (IsNullOrUndefined(obj)) continue;
             next = ToString(context, obj);
           }
@@ -321,11 +321,11 @@ namespace array_join {
 
   transitioning macro ArrayJoin<T: type>(implicit context: Context)(
       useToLocaleString: constexpr bool, receiver: JSReceiver, sep: String,
-      lenNumber: Number, locales: Object, options: Object): Object;
+      lenNumber: Number, locales: JSAny, options: JSAny): JSAny;
 
   transitioning ArrayJoin<JSArray>(implicit context: Context)(
       useToLocaleString: constexpr bool, receiver: JSReceiver, sep: String,
-      lenNumber: Number, locales: Object, options: Object): Object {
+      lenNumber: Number, locales: JSAny, options: JSAny): JSAny {
     const map: Map = receiver.map;
     const kind: ElementsKind = map.elements_kind;
     let loadFn: LoadJoinElementFn;
@@ -372,7 +372,7 @@ namespace array_join {
 
   transitioning ArrayJoin<JSTypedArray>(implicit context: Context)(
       useToLocaleString: constexpr bool, receiver: JSReceiver, sep: String,
-      lenNumber: Number, locales: Object, options: Object): Object {
+      lenNumber: Number, locales: JSAny, options: JSAny): JSAny {
     const map: Map = receiver.map;
     const kind: ElementsKind = map.elements_kind;
     let loadFn: LoadJoinElementFn;
@@ -486,7 +486,7 @@ namespace array_join {
   // Removes a receiver from the stack. The FixedArray will automatically shrink
   // to Heap::kMinJoinStackSize once the stack becomes empty.
   builtin JoinStackPop(implicit context: Context)(
-      stack: FixedArray, receiver: JSReceiver): Object {
+      stack: FixedArray, receiver: JSReceiver): JSAny {
     const len: intptr = stack.length_intptr;
     for (let i: intptr = 0; i < len; i++) {
       if (stack.objects[i] == receiver) {
@@ -526,7 +526,7 @@ namespace array_join {
   transitioning macro CycleProtectedArrayJoin<T: type>(implicit context:
                                                             Context)(
       useToLocaleString: constexpr bool, o: JSReceiver, len: Number,
-      sepObj: Object, locales: Object, options: Object): Object {
+      sepObj: JSAny, locales: JSAny, options: JSAny): JSAny {
     // 3. If separator is undefined, let sep be the single-element String ",".
     // 4. Else, let sep be ? ToString(separator).
     const sep: String =
@@ -536,7 +536,7 @@ namespace array_join {
     // the normal join algorithm.
     if (len > 0 && JoinStackPushInline(o)) {
       try {
-        const result: Object =
+        const result: JSAny =
             ArrayJoin<T>(useToLocaleString, o, sep, len, locales, options);
         JoinStackPopInline(o);
         return result;
@@ -551,9 +551,9 @@ namespace array_join {
 
   // https://tc39.github.io/ecma262/#sec-array.prototype.join
   transitioning javascript builtin
-  ArrayPrototypeJoin(js-implicit context: Context, receiver: Object)(
-      ...arguments): Object {
-    const separator: Object = arguments[0];
+  ArrayPrototypeJoin(js-implicit context: Context, receiver: JSAny)(
+      ...arguments): JSAny {
+    const separator: JSAny = arguments[0];
 
     // 1. Let O be ? ToObject(this value).
     const o: JSReceiver = ToObject_Inline(context, receiver);
@@ -571,9 +571,9 @@ namespace array_join {
 
   // https://tc39.github.io/ecma262/#sec-array.prototype.tolocalestring
   transitioning javascript builtin ArrayPrototypeToLocaleString(
-      js-implicit context: Context, receiver: Object)(...arguments): Object {
-    const locales: Object = arguments[0];
-    const options: Object = arguments[1];
+      js-implicit context: Context, receiver: JSAny)(...arguments): JSAny {
+    const locales: JSAny = arguments[0];
+    const options: JSAny = arguments[1];
 
     // 1. Let O be ? ToObject(this value).
     const o: JSReceiver = ToObject_Inline(context, receiver);
@@ -591,12 +591,12 @@ namespace array_join {
 
   // https://tc39.github.io/ecma262/#sec-array.prototype.tostring
   transitioning javascript builtin ArrayPrototypeToString(
-      js-implicit context: Context, receiver: Object)(...arguments): Object {
+      js-implicit context: Context, receiver: JSAny)(...arguments): JSAny {
     // 1. Let array be ? ToObject(this value).
     const array: JSReceiver = ToObject_Inline(context, receiver);
 
     // 2. Let func be ? Get(array, "join").
-    const prop: Object = GetProperty(array, 'join');
+    const prop: JSAny = GetProperty(array, 'join');
     try {
       // 3. If IsCallable(func) is false, let func be the intrinsic function
       //    %ObjProto_toString%.
@@ -612,8 +612,8 @@ namespace array_join {
 
   // https://tc39.github.io/ecma262/#sec-%typedarray%.prototype.join
   transitioning javascript builtin TypedArrayPrototypeJoin(
-      js-implicit context: Context, receiver: Object)(...arguments): Object {
-    const separator: Object = arguments[0];
+      js-implicit context: Context, receiver: JSAny)(...arguments): JSAny {
+    const separator: JSAny = arguments[0];
 
     // Spec: ValidateTypedArray is applied to the this value prior to evaluating
     // the algorithm.
@@ -627,9 +627,9 @@ namespace array_join {
 
   // https://tc39.github.io/ecma262/#sec-%typedarray%.prototype.tolocalestring
   transitioning javascript builtin TypedArrayPrototypeToLocaleString(
-      js-implicit context: Context, receiver: Object)(...arguments): Object {
-    const locales: Object = arguments[0];
-    const options: Object = arguments[1];
+      js-implicit context: Context, receiver: JSAny)(...arguments): JSAny {
+    const locales: JSAny = arguments[0];
+    const options: JSAny = arguments[1];
 
     // Spec: ValidateTypedArray is applied to the this value prior to evaluating
     // the algorithm.

src/builtins/array-lastindexof.tq

@@ -4,20 +4,20 @@
 
 namespace array_lastindexof {
   macro LoadWithHoleCheck<Elements: type>(
-      elements: FixedArrayBase, index: Smi): Object
+      elements: FixedArrayBase, index: Smi): JSAny
       labels IfHole;
 
   LoadWithHoleCheck<FixedArray>(implicit context: Context)(
-      elements: FixedArrayBase, index: Smi): Object
+      elements: FixedArrayBase, index: Smi): JSAny
       labels IfHole {
     const elements: FixedArray = UnsafeCast<FixedArray>(elements);
     const element: Object = elements.objects[index];
     if (element == TheHole) goto IfHole;
-    return element;
+    return UnsafeCast<JSAny>(element);
   }
 
   LoadWithHoleCheck<FixedDoubleArray>(implicit context: Context)(
-      elements: FixedArrayBase, index: Smi): Object
+      elements: FixedArrayBase, index: Smi): JSAny
       labels IfHole {
     const elements: FixedDoubleArray = UnsafeCast<FixedDoubleArray>(elements);
     const element: float64 = LoadDoubleWithHoleCheck(elements, index)
@@ -26,7 +26,7 @@ namespace array_lastindexof {
   }
 
   macro FastArrayLastIndexOf<Elements: type>(
-      context: Context, array: JSArray, from: Smi, searchElement: Object): Smi {
+      context: Context, array: JSArray, from: Smi, searchElement: JSAny): Smi {
     const elements: FixedArrayBase = array.elements;
     let k: Smi = from;
 
@@ -40,7 +40,7 @@ namespace array_lastindexof {
 
     while (k >= 0) {
       try {
-        const element: Object = LoadWithHoleCheck<Elements>(elements, k)
+        const element: JSAny = LoadWithHoleCheck<Elements>(elements, k)
             otherwise Hole;
 
         const same: Boolean = StrictEqual(searchElement, element);
@@ -80,8 +80,8 @@ namespace array_lastindexof {
   }
 
   macro TryFastArrayLastIndexOf(
-      context: Context, receiver: JSReceiver, searchElement: Object,
-      from: Number): Object
+      context: Context, receiver: JSReceiver, searchElement: JSAny,
+      from: Number): JSAny
       labels Slow {
     const array: FastJSArray = Cast<FastJSArray>(receiver) otherwise Slow;
     const length: Smi = array.length;
@@ -99,8 +99,8 @@ namespace array_lastindexof {
   }
 
   transitioning macro GenericArrayLastIndexOf(
-      context: Context, object: JSReceiver, searchElement: Object,
-      from: Number): Object {
+      context: Context, object: JSReceiver, searchElement: JSAny,
+      from: Number): JSAny {
     let k: Number = from;
 
     // 7. Repeat, while k >= 0.
@@ -111,7 +111,7 @@ namespace array_lastindexof {
       // b. If kPresent is true, then.
       if (kPresent == True) {
         // i. Let elementK be ? Get(O, ! ToString(k)).
-        const element: Object = GetProperty(object, k);
+        const element: JSAny = GetProperty(object, k);
 
         // ii. Let same be the result of performing Strict Equality Comparison
         //     searchElement === elementK.
@@ -131,7 +131,7 @@ namespace array_lastindexof {
 
   // https://tc39.github.io/ecma262/#sec-array.prototype.lastIndexOf
   transitioning javascript builtin ArrayPrototypeLastIndexOf(
-      js-implicit context: Context, receiver: Object)(...arguments): Object {
+      js-implicit context: Context, receiver: JSAny)(...arguments): JSAny {
     // 1. Let O be ? ToObject(this value).
     const object: JSReceiver = ToObject_Inline(context, receiver);
 
@@ -144,7 +144,7 @@ namespace array_lastindexof {
     // Step 4 - 6.
     const from: Number = GetFromIndex(context, length, arguments);
 
-    const searchElement: Object = arguments[0];
+    const searchElement: JSAny = arguments[0];
 
     try {
       return TryFastArrayLastIndexOf(context, object, searchElement, from)

src/builtins/array-map.tq

@@ -5,15 +5,15 @@
 namespace array_map {
   transitioning javascript builtin
   ArrayMapLoopEagerDeoptContinuation(
-      js-implicit context: Context, receiver: Object)(
-      callback: Object, thisArg: Object, array: Object, initialK: Object,
-      length: Object): Object {
+      js-implicit context: Context, receiver: JSAny)(
+      callback: JSAny, thisArg: JSAny, array: JSAny, initialK: JSAny,
+      length: JSAny): JSAny {
     // All continuation points in the optimized filter implementation are
     // after the ToObject(O) call that ensures we are dealing with a
     // JSReceiver.
     //
     // Also, this great mass of casts is necessary because the signature
-    // of Torque javascript builtins requires Object type for all parameters
+    // of Torque javascript builtins requires JSAny type for all parameters
     // other than {context}.
     const jsreceiver = Cast<JSReceiver>(receiver) otherwise unreachable;
     const callbackfn = Cast<Callable>(callback) otherwise unreachable;
@@ -28,9 +28,9 @@ namespace array_map {
 
   transitioning javascript builtin
   ArrayMapLoopLazyDeoptContinuation(
-      js-implicit context: Context, receiver: Object)(
-      callback: Object, thisArg: Object, array: Object, initialK: Object,
-      length: Object, result: Object): Object {
+      js-implicit context: Context, receiver: JSAny)(
+      callback: JSAny, thisArg: JSAny, array: JSAny, initialK: JSAny,
+      length: JSAny, result: JSAny): JSAny {
     // All continuation points in the optimized filter implementation are
     // after the ToObject(O) call that ensures we are dealing with a
     // JSReceiver.
@@ -57,9 +57,9 @@ namespace array_map {
   }
 
   transitioning builtin ArrayMapLoopContinuation(implicit context: Context)(
-      _receiver: JSReceiver, callbackfn: Callable, thisArg: Object,
+      _receiver: JSReceiver, callbackfn: Callable, thisArg: JSAny,
       array: JSReceiver, o: JSReceiver, initialK: Number,
-      length: Number): Object {
+      length: Number): JSAny {
     // 6. Let k be 0.
     // 7. Repeat, while k < len
     for (let k: Number = initialK; k < length; k++) {
@@ -73,10 +73,10 @@ namespace array_map {
       // 7c. If kPresent is true, then:
       if (kPresent == True) {
         //  i. Let kValue be ? Get(O, Pk).
-        const kValue: Object = GetProperty(o, k);
+        const kValue: JSAny = GetProperty(o, k);
 
         // ii. Let mapped_value be ? Call(callbackfn, T, kValue, k, O).
-        const mappedValue: Object =
+        const mappedValue: JSAny =
             Call(context, callbackfn, thisArg, kValue, k, o);
 
         // iii. Perform ? CreateDataPropertyOrThrow(A, Pk, mapped_value).
@@ -127,12 +127,12 @@ namespace array_map {
             SmiUntag(length), kAllowLargeObjectAllocation);
         a = NewJSArray(map, this.fixedArray);
         for (let i: Smi = 0; i < validLength; i++) {
-          typeswitch (this.fixedArray.objects[i]) {
+          typeswitch (
+              UnsafeCast<(Number | TheHole)>(this.fixedArray.objects[i])) {
             case (n: Number): {
               elements.floats[i] = Convert<float64>(n);
             }
-            case (h: HeapObject): {
-              assert(h == TheHole);
+            case (TheHole): {
             }
           }
         }
@@ -147,7 +147,7 @@ namespace array_map {
       return a;
     }
 
-    StoreResult(implicit context: Context)(index: Smi, result: Object) {
+    StoreResult(implicit context: Context)(index: Smi, result: JSAny) {
       typeswitch (result) {
         case (s: Smi): {
           this.fixedArray.objects[index] = s;
@@ -156,7 +156,7 @@ namespace array_map {
           this.onlySmis = false;
           this.fixedArray.objects[index] = s;
         }
-        case (s: HeapObject): {
+        case (s: JSAnyNotNumber): {
           this.onlySmis = false;
           this.onlyNumbers = false;
           this.fixedArray.objects[index] = s;
@@ -185,7 +185,7 @@ namespace array_map {
 
   transitioning macro FastArrayMap(implicit context: Context)(
       fastO: FastJSArrayForRead, len: Smi, callbackfn: Callable,
-      thisArg: Object): JSArray
+      thisArg: JSAny): JSArray
       labels Bailout(JSArray, Smi) {
     let k: Smi = 0;
     let fastOW = NewFastJSArrayForReadWitness(fastO);
@@ -201,9 +201,9 @@ namespace array_map {
         if (k >= fastOW.Get().length) goto PrepareBailout(k);
 
         try {
-          const value: Object = fastOW.LoadElementNoHole(k)
+          const value: JSAny = fastOW.LoadElementNoHole(k)
               otherwise FoundHole;
-          const result: Object =
+          const result: JSAny =
               Call(context, callbackfn, thisArg, value, k, fastOW.Get());
           vector.StoreResult(k, result);
         }
@@ -224,8 +224,7 @@ namespace array_map {
 
   // https://tc39.github.io/ecma262/#sec-array.prototype.map
   transitioning javascript builtin
-  ArrayMap(js-implicit context: Context, receiver: Object)(...arguments):
-      Object {
+  ArrayMap(js-implicit context: Context, receiver: JSAny)(...arguments): JSAny {
     try {
       RequireObjectCoercible(receiver, 'Array.prototype.map');
 
@@ -241,7 +240,7 @@ namespace array_map {
       const callbackfn = Cast<Callable>(arguments[0]) otherwise TypeError;
 
       // 4. If thisArg is present, let T be thisArg; else let T be undefined.
-      const thisArg: Object = arguments.length > 1 ? arguments[1] : Undefined;
+      const thisArg: JSAny = arguments.length > 1 ? arguments[1] : Undefined;
 
       let array: JSReceiver;
       let k: Number = 0;

src/builtins/array-of.tq

@@ -5,8 +5,7 @@
 namespace array_of {
   // https://tc39.github.io/ecma262/#sec-array.of
   transitioning javascript builtin
-  ArrayOf(js-implicit context: Context, receiver: Object)(...arguments):
-      Object {
+  ArrayOf(js-implicit context: Context, receiver: JSAny)(...arguments): JSAny {
     // 1. Let len be the actual number of arguments passed to this function.
     const len: Smi = Convert<Smi>(arguments.length);
 
@@ -14,7 +13,7 @@ namespace array_of {
     const items: Arguments = arguments;
 
     // 3. Let C be the this value.
-    const c: Object = receiver;
+    const c: JSAny = receiver;
 
     let a: JSReceiver;
 
@@ -24,7 +23,7 @@ namespace array_of {
         // a. Let A be ? Construct(C, « len »).
         a = Construct(c, len);
       }
-      case (Object): {
+      case (JSAny): {
         // a. Let A be ? ArrayCreate(len).
         a = ArrayCreate(len);
       }
@@ -36,7 +35,7 @@ namespace array_of {
     // 7. Repeat, while k < len
     while (k < len) {
       // a. Let kValue be items[k].
-      const kValue: Object = items[Convert<intptr>(k)];
+      const kValue: JSAny = items[Convert<intptr>(k)];
 
       // b. Let Pk be ! ToString(k).
       // c. Perform ? CreateDataPropertyOrThrow(A, Pk, kValue).

src/builtins/array-reduce-right.tq

@@ -6,13 +6,13 @@ namespace array {
   transitioning javascript builtin
   ArrayReduceRightPreLoopEagerDeoptContinuation(
       js-implicit context: Context,
-      receiver: Object)(callback: Object, length: Object): Object {
+      receiver: JSAny)(callback: JSAny, length: JSAny): JSAny {
     // All continuation points in the optimized every implementation are
     // after the ToObject(O) call that ensures we are dealing with a
     // JSReceiver.
     //
     // Also, this great mass of casts is necessary because the signature
-    // of Torque javascript builtins requires Object type for all parameters
+    // of Torque javascript builtins requires JSAny type for all parameters
     // other than {context}.
     const jsreceiver = Cast<JSReceiver>(receiver) otherwise unreachable;
     const callbackfn = Cast<Callable>(callback) otherwise unreachable;
@@ -27,15 +27,15 @@ namespace array {
 
   transitioning javascript builtin
   ArrayReduceRightLoopEagerDeoptContinuation(
-      js-implicit context: Context, receiver: Object)(
-      callback: Object, initialK: Object, length: Object,
-      accumulator: Object): Object {
+      js-implicit context: Context, receiver: JSAny)(
+      callback: JSAny, initialK: JSAny, length: JSAny,
+      accumulator: JSAny): JSAny {
     // All continuation points in the optimized every implementation are
     // after the ToObject(O) call that ensures we are dealing with a
     // JSReceiver.
     //
     // Also, this great mass of casts is necessary because the signature
-    // of Torque javascript builtins requires Object type for all parameters
+    // of Torque javascript builtins requires JSAny type for all parameters
     // other than {context}.
     const jsreceiver = Cast<JSReceiver>(receiver) otherwise unreachable;
     const callbackfn = Cast<Callable>(callback) otherwise unreachable;
@@ -48,9 +48,8 @@ namespace array {
 
   transitioning javascript builtin
   ArrayReduceRightLoopLazyDeoptContinuation(
-      js-implicit context: Context, receiver: Object)(
-      callback: Object, initialK: Object, length: Object,
-      result: Object): Object {
+      js-implicit context: Context, receiver: JSAny)(
+      callback: JSAny, initialK: JSAny, length: JSAny, result: JSAny): JSAny {
     // All continuation points in the optimized every implementation are
     // after the ToObject(O) call that ensures we are dealing with a
     // JSReceiver.
@@ -67,8 +66,9 @@ namespace array {
 
   transitioning builtin ArrayReduceRightLoopContinuation(implicit context:
                                                              Context)(
-      _receiver: JSReceiver, callbackfn: Callable, initialAccumulator: Object,
-      o: JSReceiver, initialK: Number, _length: Number): Object {
+      _receiver: JSReceiver, callbackfn: Callable,
+      initialAccumulator: JSAny | TheHole, o: JSReceiver, initialK: Number,
+      _length: Number): JSAny {
     let accumulator = initialAccumulator;
 
     // 8b and 9. Repeat, while k >= 0
@@ -83,16 +83,20 @@ namespace array {
       // 8b iii and 9c. If kPresent is true, then
       if (present == True) {
         // 8b iii and 9c i. Let kValue be ? Get(O, Pk).
-        const value: Object = GetProperty(o, k);
-
-        if (accumulator == TheHole) {
-          // 8b iii 1.
-          accumulator = value;
-        } else {
-          // 9c. ii. Set accumulator to ? Call(callbackfn, undefined,
-          //         <accumulator, kValue, k, O>).
-          accumulator =
-              Call(context, callbackfn, Undefined, accumulator, value, k, o);
+        const value: JSAny = GetProperty(o, k);
+
+        typeswitch (accumulator) {
+          case (TheHole): {
+            // 8b iii 1.
+            accumulator = value;
+          }
+          case (accumulatorNotHole: JSAny): {
+            // 9c. ii. Set accumulator to ? Call(callbackfn, undefined,
+            //         <accumulator, kValue, k, O>).
+            accumulator = Call(
+                context, callbackfn, Undefined, accumulatorNotHole, value, k,
+                o);
+          }
         }
       }
 
@@ -102,16 +106,20 @@ namespace array {
     // 8c. if kPresent is false, throw a TypeError exception.
     // If the accumulator is discovered with the sentinel hole value,
     // this means kPresent is false.
-    if (accumulator == TheHole) {
-      ThrowTypeError(kReduceNoInitial, 'Array.prototype.reduceRight');
+    typeswitch (accumulator) {
+      case (TheHole): {
+        ThrowTypeError(kReduceNoInitial, 'Array.prototype.reduceRight');
+      }
+      case (accumulator: JSAny): {
+        return accumulator;
+      }
     }
-    return accumulator;
   }
 
   transitioning macro FastArrayReduceRight(implicit context: Context)(
       o: JSReceiver, len: Number, callbackfn: Callable,
-      initialAccumulator: Object): Object
-      labels Bailout(Number, Object) {
+      initialAccumulator: JSAny | TheHole): JSAny
+      labels Bailout(Number, JSAny | TheHole) {
     let accumulator = initialAccumulator;
     const smiLen = Cast<Smi>(len) otherwise goto Bailout(len - 1, accumulator);
     const fastO = Cast<FastJSArrayForRead>(o)
@@ -125,25 +133,32 @@ namespace array {
       // Ensure that we haven't walked beyond a possibly updated length.
       if (k >= fastOW.Get().length) goto Bailout(k, accumulator);
 
-      const value: Object = fastOW.LoadElementNoHole(k) otherwise continue;
-      if (accumulator == TheHole) {
-        accumulator = value;
-      } else {
-        accumulator = Call(
-            context, callbackfn, Undefined, accumulator, value, k,
-            fastOW.Get());
+      const value: JSAny = fastOW.LoadElementNoHole(k) otherwise continue;
+      typeswitch (accumulator) {
+        case (TheHole): {
+          accumulator = value;
+        }
+        case (accumulatorNotHole: JSAny): {
+          accumulator = Call(
+              context, callbackfn, Undefined, accumulatorNotHole, value, k,
+              fastOW.Get());
+        }
       }
     }
-    if (accumulator == TheHole) {
-      ThrowTypeError(kReduceNoInitial, 'Array.prototype.reduceRight');
+    typeswitch (accumulator) {
+      case (TheHole): {
+        ThrowTypeError(kReduceNoInitial, 'Array.prototype.reduceRight');
+      }
+      case (accumulator: JSAny): {
+        return accumulator;
+      }
     }
-    return accumulator;
   }
 
   // https://tc39.github.io/ecma262/#sec-array.prototype.reduceRight
   transitioning javascript builtin
-  ArrayReduceRight(js-implicit context: Context, receiver: Object)(
-      ...arguments): Object {
+  ArrayReduceRight(js-implicit context: Context, receiver: JSAny)(...arguments):
+      JSAny {
     try {
       RequireObjectCoercible(receiver, 'Array.prototype.reduceRight');
 
@@ -163,14 +178,14 @@ namespace array {
       // exception. (This case is handled at the end of
       // ArrayReduceRightLoopContinuation).
 
-      const initialValue: Object =
+      const initialValue: JSAny | TheHole =
           arguments.length > 1 ? arguments[1] : TheHole;
 
       try {
         return FastArrayReduceRight(o, len, callbackfn, initialValue)
             otherwise Bailout;
       }
-      label Bailout(value: Number, accumulator: Object) {
+      label Bailout(value: Number, accumulator: JSAny | TheHole) {
         return ArrayReduceRightLoopContinuation(
             o, callbackfn, accumulator, o, value, len);
       }

src/builtins/array-reduce.tq

@@ -6,13 +6,13 @@ namespace array {
   transitioning javascript builtin
   ArrayReducePreLoopEagerDeoptContinuation(
       js-implicit context: Context,
-      receiver: Object)(callback: Object, length: Object): Object {
+      receiver: JSAny)(callback: JSAny, length: JSAny): JSAny {
     // All continuation points in the optimized every implementation are
     // after the ToObject(O) call that ensures we are dealing with a
     // JSReceiver.
     //
     // Also, this great mass of casts is necessary because the signature
-    // of Torque javascript builtins requires Object type for all parameters
+    // of Torque javascript builtins requires JSAny type for all parameters
     // other than {context}.
     const jsreceiver = Cast<JSReceiver>(receiver) otherwise unreachable;
     const callbackfn = Cast<Callable>(callback) otherwise unreachable;
@@ -27,15 +27,15 @@ namespace array {
 
   transitioning javascript builtin
   ArrayReduceLoopEagerDeoptContinuation(
-      js-implicit context: Context, receiver: Object)(
-      callback: Object, initialK: Object, length: Object,
-      accumulator: Object): Object {
+      js-implicit context: Context, receiver: JSAny)(
+      callback: JSAny, initialK: JSAny, length: JSAny,
+      accumulator: JSAny): JSAny {
     // All continuation points in the optimized every implementation are
     // after the ToObject(O) call that ensures we are dealing with a
     // JSReceiver.
     //
     // Also, this great mass of casts is necessary because the signature
-    // of Torque javascript builtins requires Object type for all parameters
+    // of Torque javascript builtins requires JSAny type for all parameters
     // other than {context}.
     const jsreceiver = Cast<JSReceiver>(receiver) otherwise unreachable;
     const callbackfn = Cast<Callable>(callback) otherwise unreachable;
@@ -48,9 +48,8 @@ namespace array {
 
   transitioning javascript builtin
   ArrayReduceLoopLazyDeoptContinuation(
-      js-implicit context: Context, receiver: Object)(
-      callback: Object, initialK: Object, length: Object,
-      result: Object): Object {
+      js-implicit context: Context, receiver: JSAny)(
+      callback: JSAny, initialK: JSAny, length: JSAny, result: JSAny): JSAny {
     // All continuation points in the optimized every implementation are
     // after the ToObject(O) call that ensures we are dealing with a
     // JSReceiver.
@@ -66,8 +65,9 @@ namespace array {
   }
 
   transitioning builtin ArrayReduceLoopContinuation(implicit context: Context)(
-      _receiver: JSReceiver, callbackfn: Callable, initialAccumulator: Object,
-      o: JSReceiver, initialK: Number, length: Number): Object {
+      _receiver: JSReceiver, callbackfn: Callable,
+      initialAccumulator: JSAny | TheHole, o: JSReceiver, initialK: Number,
+      length: Number): JSAny {
     let accumulator = initialAccumulator;
 
     // 8b and 9. Repeat, while k < len
@@ -82,16 +82,20 @@ namespace array {
       // 6c. If kPresent is true, then
       if (present == True) {
         // 6c. i. Let kValue be ? Get(O, Pk).
-        const value: Object = GetProperty(o, k);
-
-        if (accumulator == TheHole) {
-          // 8b.
-          accumulator = value;
-        } else {
-          // 9c. ii. Set accumulator to ? Call(callbackfn, undefined,
-          //         <accumulator, kValue, k, O>).
-          accumulator =
-              Call(context, callbackfn, Undefined, accumulator, value, k, o);
+        const value: JSAny = GetProperty(o, k);
+
+        typeswitch (accumulator) {
+          case (TheHole): {
+            // 8b.
+            accumulator = value;
+          }
+          case (accumulatorNotHole: JSAny): {
+            // 9c. ii. Set accumulator to ? Call(callbackfn, undefined,
+            //         <accumulator, kValue, k, O>).
+            accumulator = Call(
+                context, callbackfn, Undefined, accumulatorNotHole, value, k,
+                o);
+          }
         }
       }
 
@@ -101,16 +105,20 @@ namespace array {
     // 8c. if kPresent is false, throw a TypeError exception.
     // If the accumulator is discovered with the sentinel hole value,
     // this means kPresent is false.
-    if (accumulator == TheHole) {
-      ThrowTypeError(kReduceNoInitial, 'Array.prototype.reduce');
+    typeswitch (accumulator) {
+      case (TheHole): {
+        ThrowTypeError(kReduceNoInitial, 'Array.prototype.reduce');
+      }
+      case (accumulator: JSAny): {
+        return accumulator;
+      }
     }
-    return accumulator;
   }
 
   transitioning macro FastArrayReduce(implicit context: Context)(
       o: JSReceiver, len: Number, callbackfn: Callable,
-      initialAccumulator: Object): Object
-      labels Bailout(Number, Object) {
+      initialAccumulator: JSAny | TheHole): JSAny
+      labels Bailout(Number, JSAny | TheHole) {
     const k = 0;
     let accumulator = initialAccumulator;
     Cast<Smi>(len) otherwise goto Bailout(k, accumulator);
@@ -125,25 +133,32 @@ namespace array {
       // Ensure that we haven't walked beyond a possibly updated length.
       if (k >= fastOW.Get().length) goto Bailout(k, accumulator);
 
-      const value: Object = fastOW.LoadElementNoHole(k) otherwise continue;
-      if (accumulator == TheHole) {
-        accumulator = value;
-      } else {
-        accumulator = Call(
-            context, callbackfn, Undefined, accumulator, value, k,
-            fastOW.Get());
+      const value: JSAny = fastOW.LoadElementNoHole(k) otherwise continue;
+      typeswitch (accumulator) {
+        case (TheHole): {
+          accumulator = value;
+        }
+        case (accumulatorNotHole: JSAny): {
+          accumulator = Call(
+              context, callbackfn, Undefined, accumulatorNotHole, value, k,
+              fastOW.Get());
+        }
       }
     }
-    if (accumulator == TheHole) {
-      ThrowTypeError(kReduceNoInitial, 'Array.prototype.reduce');
+    typeswitch (accumulator) {
+      case (TheHole): {
+        ThrowTypeError(kReduceNoInitial, 'Array.prototype.reduce');
+      }
+      case (accumulator: JSAny): {
+        return accumulator;
+      }
     }
-    return accumulator;
   }
 
   // https://tc39.github.io/ecma262/#sec-array.prototype.reduce
   transitioning javascript builtin
-  ArrayReduce(js-implicit context: Context, receiver: Object)(...arguments):
-      Object {
+  ArrayReduce(js-implicit context: Context, receiver: JSAny)(...arguments):
+      JSAny {
     try {
       RequireObjectCoercible(receiver, 'Array.prototype.reduce');
 
@@ -163,14 +178,14 @@ namespace array {
       // exception. (This case is handled at the end of
       // ArrayReduceLoopContinuation).
 
-      const initialValue: Object =
+      const initialValue: JSAny | TheHole =
           arguments.length > 1 ? arguments[1] : TheHole;
 
       try {
         return FastArrayReduce(o, len, callbackfn, initialValue)
             otherwise Bailout;
       }
-      label Bailout(value: Number, accumulator: Object) {
+      label Bailout(value: Number, accumulator: JSAny | TheHole) {
         return ArrayReduceLoopContinuation(
             o, callbackfn, accumulator, o, value, len);
       }

src/builtins/array-reverse.tq

@@ -12,10 +12,10 @@ namespace array_reverse {
     return UnsafeCast<Smi>(elements.objects[index]);
   }
 
-  LoadElement<array::FastPackedObjectElements, Object>(
-      implicit context: Context)(elements: FixedArrayBase, index: Smi): Object {
+  LoadElement<array::FastPackedObjectElements, JSAny>(
+      implicit context: Context)(elements: FixedArrayBase, index: Smi): JSAny {
     const elements: FixedArray = UnsafeCast<FixedArray>(elements);
-    return elements.objects[index];
+    return UnsafeCast<JSAny>(elements.objects[index]);
   }
 
   LoadElement<array::FastPackedDoubleElements, float64>(
@@ -38,9 +38,9 @@ namespace array_reverse {
     StoreFixedArrayElement(elems, index, value, SKIP_WRITE_BARRIER);
   }
 
-  StoreElement<array::FastPackedObjectElements, Object>(
+  StoreElement<array::FastPackedObjectElements, JSAny>(
       implicit context:
-          Context)(elements: FixedArrayBase, index: Smi, value: Object) {
+          Context)(elements: FixedArrayBase, index: Smi, value: JSAny) {
     const elements: FixedArray = UnsafeCast<FixedArray>(elements);
     elements.objects[index] = value;
   }
@@ -70,8 +70,8 @@ namespace array_reverse {
     }
   }
 
-  transitioning macro GenericArrayReverse(context: Context, receiver: Object):
-      Object {
+  transitioning macro GenericArrayReverse(context: Context, receiver: JSAny):
+      JSAny {
     // 1. Let O be ? ToObject(this value).
     const object: JSReceiver = ToObject_Inline(context, receiver);
 
@@ -89,8 +89,8 @@ namespace array_reverse {
     let upper: Number = length - 1;
 
     while (lower < upper) {
-      let lowerValue: Object = Undefined;
-      let upperValue: Object = Undefined;
+      let lowerValue: JSAny = Undefined;
+      let upperValue: JSAny = Undefined;
 
       // b. Let upperP be ! ToString(upper).
       // c. Let lowerP be ! ToString(lower).
@@ -142,7 +142,7 @@ namespace array_reverse {
     return object;
   }
 
-  macro TryFastPackedArrayReverse(implicit context: Context)(receiver: Object)
+  macro TryFastPackedArrayReverse(implicit context: Context)(receiver: JSAny)
       labels Slow {
     const array: FastJSArray = Cast<FastJSArray>(receiver) otherwise Slow;
 
@@ -153,7 +153,7 @@ namespace array_reverse {
           array.elements, array.length);
     } else if (kind == PACKED_ELEMENTS) {
       array::EnsureWriteableFastElements(array);
-      FastPackedArrayReverse<array::FastPackedObjectElements, Object>(
+      FastPackedArrayReverse<array::FastPackedObjectElements, JSAny>(
           array.elements, array.length);
     } else if (kind == PACKED_DOUBLE_ELEMENTS) {
       FastPackedArrayReverse<array::FastPackedDoubleElements, float64>(
@@ -165,7 +165,7 @@ namespace array_reverse {
 
   // https://tc39.github.io/ecma262/#sec-array.prototype.reverse
   transitioning javascript builtin ArrayPrototypeReverse(
-      js-implicit context: Context, receiver: Object)(...arguments): Object {
+      js-implicit context: Context, receiver: JSAny)(...arguments): JSAny {
     try {
       TryFastPackedArrayReverse(receiver) otherwise Baseline;
       return receiver;

src/builtins/array-shift.tq

@@ -3,9 +3,9 @@
 // found in the LICENSE file.
 
 namespace array_shift {
-  extern builtin ArrayShift(Context, JSFunction, Object, int32): Object;
+  extern builtin ArrayShift(Context, JSFunction, JSAny, int32): JSAny;
 
-  macro TryFastArrayShift(implicit context: Context)(receiver: Object): Object
+  macro TryFastArrayShift(implicit context: Context)(receiver: JSAny): JSAny
       labels Slow, Runtime {
     const array: FastJSArray = Cast<FastJSArray>(receiver) otherwise Slow;
     let witness = NewFastJSArrayWitness(array);
@@ -37,7 +37,7 @@ namespace array_shift {
   }
 
   transitioning macro GenericArrayShift(implicit context:
-                                            Context)(receiver: Object): Object {
+                                            Context)(receiver: JSAny): JSAny {
     // 1. Let O be ? ToObject(this value).
     const object: JSReceiver = ToObject_Inline(context, receiver);
 
@@ -70,7 +70,7 @@ namespace array_shift {
       // d. If fromPresent is true, then
       if (fromPresent == True) {
         // i. Let fromVal be ? Get(O, from).
-        const fromValue: Object = GetProperty(object, from);
+        const fromValue: JSAny = GetProperty(object, from);
 
         // ii. Perform ? Set(O, to, fromValue, true).
         SetProperty(object, to, fromValue);
@@ -95,7 +95,7 @@ namespace array_shift {
 
   // https://tc39.github.io/ecma262/#sec-array.prototype.shift
   transitioning javascript builtin ArrayPrototypeShift(
-      js-implicit context: Context, receiver: Object)(...arguments): Object {
+      js-implicit context: Context, receiver: JSAny)(...arguments): JSAny {
     try {
       return TryFastArrayShift(receiver) otherwise Slow, Runtime;
     }

src/builtins/array-slice.tq

@@ -63,9 +63,9 @@ namespace array_slice {
     for (let current: Smi = start; current < to; ++current) {
       const e: Object =
           sloppyElements.objects[current + kSloppyArgumentsParameterMapStart];
-      const newElement: Object = e != TheHole ?
-          argumentsContext[UnsafeCast<Smi>(e)] :
-          unmappedElements.objects[current];
+      const newElement: JSAny = UnsafeCast<JSAny>(
+          e != TheHole ? argumentsContext[UnsafeCast<Smi>(e)] :
+                         unmappedElements.objects[current]);
       // It is safe to skip the write barrier here because resultElements was
       // allocated together with result in a folded allocation.
       // TODO(tebbi): The verification of this fails at the moment due to
@@ -86,7 +86,7 @@ namespace array_slice {
   }
 
   macro HandleFastSlice(
-      context: Context, o: Object, startNumber: Number,
+      context: Context, o: JSAny, startNumber: Number,
       countNumber: Number): JSArray
       labels Bailout {
     const start: Smi = Cast<Smi>(startNumber) otherwise Bailout;
@@ -114,7 +114,7 @@ namespace array_slice {
               otherwise Bailout;
         }
       }
-      case (Object): {
+      case (JSAny): {
       }
     }
     goto Bailout;
@@ -122,15 +122,15 @@ namespace array_slice {
 
   // https://tc39.github.io/ecma262/#sec-array.prototype.slice
   transitioning javascript builtin
-  ArrayPrototypeSlice(js-implicit context: Context, receiver: Object)(
-      ...arguments): Object {
+  ArrayPrototypeSlice(js-implicit context: Context, receiver: JSAny)(
+      ...arguments): JSAny {
     // Handle array cloning case if the receiver is a fast array.
     if (arguments.length == 0) {
       typeswitch (receiver) {
         case (a: FastJSArrayForCopy): {
           return CloneFastJSArray(context, a);
         }
-        case (Object): {
+        case (JSAny): {
         }
       }
     }
@@ -142,7 +142,7 @@ namespace array_slice {
     const len: Number = GetLengthProperty(o);
 
     // 3. Let relativeStart be ? ToInteger(start).
-    const start: Object = arguments[0];
+    const start: JSAny = arguments[0];
     const relativeStart: Number = ToInteger_Inline(context, start);
 
     // 4. If relativeStart < 0, let k be max((len + relativeStart), 0);
@@ -152,7 +152,7 @@ namespace array_slice {
 
     // 5. If end is undefined, let relativeEnd be len;
     //    else let relativeEnd be ? ToInteger(end).
-    const end: Object = arguments[1];
+    const end: JSAny = arguments[1];
     const relativeEnd: Number =
         end == Undefined ? len : ToInteger_Inline(context, end);
 
@@ -193,7 +193,7 @@ namespace array_slice {
       // c. If kPresent is true, then
       if (fromPresent == True) {
         // i. Let kValue be ? Get(O, Pk).
-        const kValue: Object = GetProperty(o, pK);
+        const kValue: JSAny = GetProperty(o, pK);
 
         // ii. Perform ? CreateDataPropertyOrThrow(A, ! ToString(n), kValue).
         FastCreateDataProperty(a, n, kValue);

src/builtins/array-some.tq

@@ -5,15 +5,14 @@
 namespace array {
   transitioning javascript builtin
   ArraySomeLoopEagerDeoptContinuation(
-      js-implicit context: Context, receiver: Object)(
-      callback: Object, thisArg: Object, initialK: Object,
-      length: Object): Object {
+      js-implicit context: Context, receiver: JSAny)(
+      callback: JSAny, thisArg: JSAny, initialK: JSAny, length: JSAny): JSAny {
     // All continuation points in the optimized some implementation are
     // after the ToObject(O) call that ensures we are dealing with a
     // JSReceiver.
     //
     // Also, this great mass of casts is necessary because the signature
-    // of Torque javascript builtins requires Object type for all parameters
+    // of Torque javascript builtins requires JSAny type for all parameters
     // other than {context}.
     const jsreceiver = Cast<JSReceiver>(receiver) otherwise unreachable;
     const callbackfn = Cast<Callable>(callback) otherwise unreachable;
@@ -27,9 +26,9 @@ namespace array {
 
   transitioning javascript builtin
   ArraySomeLoopLazyDeoptContinuation(
-      js-implicit context: Context, receiver: Object)(
-      callback: Object, thisArg: Object, initialK: Object, length: Object,
-      result: Object): Object {
+      js-implicit context: Context, receiver: JSAny)(
+      callback: JSAny, thisArg: JSAny, initialK: JSAny, length: JSAny,
+      result: JSAny): JSAny {
     // All continuation points in the optimized some implementation are
     // after the ToObject(O) call that ensures we are dealing with a
     // JSReceiver.
@@ -53,9 +52,9 @@ namespace array {
   }
 
   transitioning builtin ArraySomeLoopContinuation(implicit context: Context)(
-      _receiver: JSReceiver, callbackfn: Callable, thisArg: Object,
-      _array: Object, o: JSReceiver, initialK: Number, length: Number,
-      _initialTo: Object): Object {
+      _receiver: JSReceiver, callbackfn: Callable, thisArg: JSAny,
+      _array: JSAny, o: JSReceiver, initialK: Number, length: Number,
+      _initialTo: JSAny): JSAny {
     // 5. Let k be 0.
     // 6. Repeat, while k < len
     for (let k: Number = initialK; k < length; k++) {
@@ -69,10 +68,10 @@ namespace array {
       // 6c. If kPresent is true, then
       if (kPresent == True) {
         // 6c. i. Let kValue be ? Get(O, Pk).
-        const kValue: Object = GetProperty(o, k);
+        const kValue: JSAny = GetProperty(o, k);
 
         // 6c. ii. Perform ? Call(callbackfn, T, <kValue, k, O>).
-        const result: Object = Call(context, callbackfn, thisArg, kValue, k, o);
+        const result: JSAny = Call(context, callbackfn, thisArg, kValue, k, o);
 
         // iii. If selected is true, then...
         if (ToBoolean(result)) {
@@ -86,7 +85,7 @@ namespace array {
   }
 
   transitioning macro FastArraySome(implicit context: Context)(
-      o: JSReceiver, len: Number, callbackfn: Callable, thisArg: Object): Object
+      o: JSReceiver, len: Number, callbackfn: Callable, thisArg: JSAny): JSAny
       labels Bailout(Smi) {
     let k: Smi = 0;
     const smiLen = Cast<Smi>(len) otherwise goto Bailout(k);
@@ -99,8 +98,8 @@ namespace array {
 
       // Ensure that we haven't walked beyond a possibly updated length.
       if (k >= fastOW.Get().length) goto Bailout(k);
-      const value: Object = fastOW.LoadElementNoHole(k) otherwise continue;
-      const result: Object =
+      const value: JSAny = fastOW.LoadElementNoHole(k) otherwise continue;
+      const result: JSAny =
           Call(context, callbackfn, thisArg, value, k, fastOW.Get());
       if (ToBoolean(result)) {
         return True;
@@ -111,8 +110,8 @@ namespace array {
 
   // https://tc39.github.io/ecma262/#sec-array.prototype.some
   transitioning javascript builtin
-  ArraySome(js-implicit context: Context, receiver: Object)(...arguments):
-      Object {
+  ArraySome(js-implicit context: Context, receiver: JSAny)(...arguments):
+      JSAny {
     try {
       RequireObjectCoercible(receiver, 'Array.prototype.some');
 
@@ -129,7 +128,7 @@ namespace array {
       const callbackfn = Cast<Callable>(arguments[0]) otherwise TypeError;
 
       // 4. If thisArg is present, let T be thisArg; else let T be undefined.
-      const thisArg: Object = arguments.length > 1 ? arguments[1] : Undefined;
+      const thisArg: JSAny = arguments.length > 1 ? arguments[1] : Undefined;
 
       // Special cases.
       try {

src/builtins/array-splice.tq

@@ -95,7 +95,7 @@ namespace array_splice {
       const typedNewElements: FixedArrayType =
           UnsafeCast<FixedArrayType>(a.elements);
       for (let i: intptr = 2; i < args.length; ++i) {
-        const e: Object = args[i];
+        const e: JSAny = args[i];
         // The argument elements were already validated to be an appropriate
         // {ElementType} to store in {FixedArrayType}.
         typedNewElements[k++] = UnsafeCast<ElementType>(e);
@@ -109,7 +109,7 @@ namespace array_splice {
   transitioning macro FastArraySplice(
       context: Context, args: Arguments, o: JSReceiver,
       originalLengthNumber: Number, actualStartNumber: Number, insertCount: Smi,
-      actualDeleteCountNumber: Number): Object
+      actualDeleteCountNumber: Number): JSAny
       labels Bailout {
     const originalLength: Smi =
         Cast<Smi>(originalLengthNumber) otherwise Bailout;
@@ -132,7 +132,7 @@ namespace array_splice {
 
     const oldElementsKind: ElementsKind = elementsKind;
     for (let i: intptr = 2; i < args.length; ++i) {
-      const e: Object = args[i];
+      const e: JSAny = args[i];
       if (IsFastSmiElementsKind(elementsKind)) {
         if (TaggedIsNotSmi(e)) {
           const heapObject: HeapObject = UnsafeCast<HeapObject>(e);
@@ -166,7 +166,7 @@ namespace array_splice {
     }
 
     if (IsFastSmiOrTaggedElementsKind(elementsKind)) {
-      FastSplice<FixedArray, Object>(
+      FastSplice<FixedArray, JSAny>(
           args, a, length, newLength, actualStart, insertCount,
           actualDeleteCount);
     } else {
@@ -180,7 +180,7 @@ namespace array_splice {
 
   transitioning macro FillDeletedElementsArray(
       context: Context, o: JSReceiver, actualStart: Number,
-      actualDeleteCount: Number, a: JSReceiver): Object {
+      actualDeleteCount: Number, a: JSReceiver): JSAny {
     // 10. Let k be 0.
     let k: Number = 0;
 
@@ -195,7 +195,7 @@ namespace array_splice {
       // c. If fromPresent is true, then
       if (fromPresent == True) {
         // i. Let fromValue be ? Get(O, from).
-        const fromValue: Object = GetProperty(o, from);
+        const fromValue: JSAny = GetProperty(o, from);
 
         // ii. Perform ? CreateDataPropertyOrThrow(A, ! ToString(k), fromValue).
         FastCreateDataProperty(a, k, fromValue);
@@ -231,7 +231,7 @@ namespace array_splice {
       // iv. If fromPresent is true, then
       if (fromPresent == True) {
         // 1. Let fromValue be ? Get(O, from).
-        const fromValue: Object = GetProperty(o, from);
+        const fromValue: JSAny = GetProperty(o, from);
 
         // 2. Perform ? Set(O, to, fromValue, true).
         SetProperty(o, to, fromValue);
@@ -280,7 +280,7 @@ namespace array_splice {
       // iv. If fromPresent is true, then
       if (fromPresent == True) {
         // 1. Let fromValue be ? Get(O, from).
-        const fromValue: Object = GetProperty(o, from);
+        const fromValue: JSAny = GetProperty(o, from);
 
         // 2. Perform ? Set(O, to, fromValue, true).
         SetProperty(o, to, fromValue);
@@ -298,8 +298,7 @@ namespace array_splice {
 
   transitioning macro SlowSplice(
       context: Context, arguments: Arguments, o: JSReceiver, len: Number,
-      actualStart: Number, insertCount: Smi,
-      actualDeleteCount: Number): Object {
+      actualStart: Number, insertCount: Smi, actualDeleteCount: Number): JSAny {
     // 9. Let A be ? ArraySpeciesCreate(O, actualDeleteCount).
     const a: JSReceiver = ArraySpeciesCreate(context, o, actualDeleteCount);
     const itemCount: Number = insertCount;
@@ -332,7 +331,7 @@ namespace array_splice {
     //   element.
     if (arguments.length > 2) {
       for (let i: intptr = 2; i < arguments.length; ++i) {
-        const e: Object = arguments[i];
+        const e: JSAny = arguments[i];
         // b. Perform ? Set(O, ! ToString(k), E, true).
         SetProperty(o, k, e);
 
@@ -350,8 +349,8 @@ namespace array_splice {
 
   // https://tc39.github.io/ecma262/#sec-array.prototype.splice
   transitioning javascript builtin
-  ArrayPrototypeSplice(js-implicit context: Context, receiver: Object)(
-      ...arguments): Object {
+  ArrayPrototypeSplice(js-implicit context: Context, receiver: JSAny)(
+      ...arguments): JSAny {
     // 1. Let O be ? ToObject(this value).
     const o: JSReceiver = ToObject(context, receiver);
 
@@ -359,7 +358,7 @@ namespace array_splice {
     const len: Number = GetLengthProperty(o);
 
     // 3. Let relativeStart be ? ToInteger(start).
-    const start: Object = arguments[0];
+    const start: JSAny = arguments[0];
     const relativeStart: Number = ToInteger_Inline(context, start);
 
     // 4. If relativeStart < 0, let actualStart be max((len + relativeStart),
@@ -388,7 +387,7 @@ namespace array_splice {
       // a. Let insertCount be the Number of actual arguments minus 2.
       insertCount = Convert<Smi>(arguments.length) - 2;
       // b. Let dc be ? ToInteger(deleteCount).
-      const deleteCount: Object = arguments[1];
+      const deleteCount: JSAny = arguments[1];
       const dc: Number = ToInteger_Inline(context, deleteCount);
       // c. Let actualDeleteCount be min(max(dc, 0), len - actualStart).
       actualDeleteCount = Min(Max(dc, 0), len - actualStart);

src/builtins/array-unshift.tq

@@ -3,10 +3,10 @@
 // found in the LICENSE file.
 
 namespace array_unshift {
-  extern builtin ArrayUnshift(Context, JSFunction, Object, int32): Object;
+  extern builtin ArrayUnshift(Context, JSFunction, JSAny, int32): JSAny;
 
   transitioning macro GenericArrayUnshift(
-      context: Context, receiver: Object, arguments: Arguments): Number {
+      context: Context, receiver: JSAny, arguments: Arguments): Number {
     // 1. Let O be ? ToObject(this value).
     const object: JSReceiver = ToObject_Inline(context, receiver);
 
@@ -40,7 +40,7 @@ namespace array_unshift {
         // iv. If fromPresent is true, then
         if (fromPresent == True) {
           // 1. Let fromValue be ? Get(O, from).
-          const fromValue: Object = GetProperty(object, from);
+          const fromValue: JSAny = GetProperty(object, from);
 
           // 2. Perform ? Set(O, to, fromValue, true).
           SetProperty(object, to, fromValue);
@@ -78,7 +78,7 @@ namespace array_unshift {
 
   // https://tc39.github.io/ecma262/#sec-array.prototype.unshift
   transitioning javascript builtin ArrayPrototypeUnshift(
-      js-implicit context: Context, receiver: Object)(...arguments): Object {
+      js-implicit context: Context, receiver: JSAny)(...arguments): JSAny {
     try {
       const array: FastJSArray = Cast<FastJSArray>(receiver) otherwise Slow;
       array::EnsureWriteableFastElements(array);

src/builtins/array.tq

@@ -32,30 +32,15 @@ namespace array {
     assert(array.elements.map != kCOWMap);
   }
 
-  macro IsJSArray(implicit context: Context)(o: Object): bool {
-    typeswitch (o) {
-      case (JSArray): {
-        return true;
-      }
-      case (Object): {
-        return false;
-      }
-    }
-  }
-
-  macro LoadElementOrUndefined(a: FixedArray, i: Smi): Object {
-    const e: Object = a.objects[i];
-    return e == TheHole ? Undefined : e;
+  macro LoadElementOrUndefined(implicit context:
+                                   Context)(a: FixedArray, i: Smi): JSAny {
+    const e = UnsafeCast<(JSAny | TheHole)>(a.objects[i]);
+    return ReplaceTheHoleWithUndefined(e);
   }
 
   macro LoadElementOrUndefined(a: FixedDoubleArray, i: Smi): NumberOrUndefined {
-    try {
-      const f: float64 = LoadDoubleWithHoleCheck(a, i) otherwise IfHole;
-      return AllocateHeapNumberWithValue(f);
-    }
-    label IfHole {
-      return Undefined;
-    }
+    const f: float64 = LoadDoubleWithHoleCheck(a, i) otherwise return Undefined;
+    return AllocateHeapNumberWithValue(f);
   }
 
   macro StoreArrayHole(elements: FixedDoubleArray, k: Smi): void {
@@ -66,5 +51,5 @@ namespace array {
     elements.objects[k] = TheHole;
   }
 
-  extern macro SetPropertyLength(implicit context: Context)(Object, Number);
+  extern macro SetPropertyLength(implicit context: Context)(JSAny, Number);
 }

src/builtins/boolean.tq

@@ -5,8 +5,8 @@
 namespace boolean {
   javascript builtin
   BooleanConstructor(
-      js-implicit context: Context, receiver: Object, newTarget: Object,
-      target: JSFunction)(...arguments): Object {
+      js-implicit context: Context, receiver: JSAny, newTarget: JSAny,
+      target: JSFunction)(...arguments): JSAny {
     const value = SelectBooleanConstant(ToBoolean(arguments[0]));
 
     if (newTarget == Undefined) {

src/builtins/collections.tq

@@ -6,7 +6,7 @@
 
 namespace collections {
   @export
-  macro LoadKeyValuePairNoSideEffects(implicit context: Context)(o: Object):
+  macro LoadKeyValuePairNoSideEffects(implicit context: Context)(o: JSAny):
       KeyValuePair labels MayHaveSideEffects {
     typeswitch (o) {
       case (a: FastJSArray): {
@@ -28,7 +28,7 @@ namespace collections {
                                   Undefined
             };
           }
-          case (Object): deferred {
+          case (FixedArrayBase): deferred {
             unreachable;
           }
         }
@@ -36,14 +36,14 @@ namespace collections {
       case (JSReceiver): {
         goto MayHaveSideEffects;
       }
-      case (o: Object): deferred {
+      case (o: JSAny): deferred {
         ThrowTypeError(kIteratorValueNotAnObject, o);
       }
     }
   }
 
   @export
-  transitioning macro LoadKeyValuePair(implicit context: Context)(o: Object):
+  transitioning macro LoadKeyValuePair(implicit context: Context)(o: JSAny):
       KeyValuePair {
     try {
       return LoadKeyValuePairNoSideEffects(o) otherwise Generic;

src/builtins/extras-utils.tq

@@ -3,23 +3,22 @@
 // found in the LICENSE file.
 
 namespace extras_utils {
-  extern runtime CreatePrivateSymbol(Context, Object): HeapObject;
-  extern runtime PromiseMarkAsHandled(Context, Object): Undefined;
-  extern runtime PromiseStatus(Context, Object): Smi;
+  extern runtime CreatePrivateSymbol(Context, JSAny): HeapObject;
+  extern runtime PromiseMarkAsHandled(Context, JSAny): Undefined;
+  extern runtime PromiseStatus(Context, JSAny): Smi;
 
   javascript builtin ExtrasUtilsCreatePrivateSymbol(
-      js-implicit context: Context,
-      receiver: Object)(...arguments): HeapObject {
+      js-implicit context: Context, receiver: JSAny)(...arguments): HeapObject {
     return CreatePrivateSymbol(context, arguments[0]);
   }
 
   javascript builtin ExtrasUtilsMarkPromiseAsHandled(
-      js-implicit context: Context, receiver: Object)(...arguments): Undefined {
+      js-implicit context: Context, receiver: JSAny)(...arguments): Undefined {
     return PromiseMarkAsHandled(context, arguments[0]);
   }
 
   javascript builtin ExtrasUtilsPromiseState(
-      js-implicit context: Context, receiver: Object)(...arguments): Smi {
+      js-implicit context: Context, receiver: JSAny)(...arguments): Smi {
     return PromiseStatus(context, arguments[0]);
   }
 }

src/builtins/internal-coverage.tq

@@ -51,7 +51,7 @@ namespace internal_coverage {
   }
 
   builtin IncBlockCounter(implicit context: Context)(
-      function: JSFunction, coverageArraySlotIndex: Smi): Object {
+      function: JSFunction, coverageArraySlotIndex: Smi): Undefined {
     // It's quite possible that a function contains IncBlockCounter bytecodes,
     // but no coverage info exists. This happens e.g. by selecting the
     // best-effort coverage collection mode, which triggers deletion of all

src/builtins/iterator.tq

@@ -11,13 +11,13 @@ namespace iterator {
     object: JSReceiver;
 
     // iteratorRecord.[[NextMethod]]
-    next: Object;
+    next: JSAny;
   }
 
   extern macro IteratorBuiltinsAssembler::GetIteratorMethod(
-      implicit context: Context)(Object): Object;
+      implicit context: Context)(JSAny): JSAny;
   extern macro IteratorBuiltinsAssembler::GetIterator(
-      implicit context: Context)(Object): IteratorRecord;
+      implicit context: Context)(JSAny): IteratorRecord;
 
   extern macro IteratorBuiltinsAssembler::IteratorStep(
       implicit context: Context)(IteratorRecord): JSReceiver
@@ -27,18 +27,18 @@ namespace iterator {
       labels Done;
 
   extern macro IteratorBuiltinsAssembler::IteratorValue(
-      implicit context: Context)(JSReceiver): Object;
+      implicit context: Context)(JSReceiver): JSAny;
   extern macro IteratorBuiltinsAssembler::IteratorValue(
-      implicit context: Context)(JSReceiver, Map): Object;
+      implicit context: Context)(JSReceiver, Map): JSAny;
 
   extern macro IteratorBuiltinsAssembler::IteratorCloseOnException(
-      implicit context: Context)(IteratorRecord, Object): never;
+      implicit context: Context)(IteratorRecord, JSAny): never;
 
   extern macro IteratorBuiltinsAssembler::IterableToList(
-      implicit context: Context)(Object, Object): JSArray;
+      implicit context: Context)(JSAny, JSAny): JSArray;
 
   extern builtin IterableToListMayPreserveHoles(implicit context:
-                                                    Context)(Object, Object);
+                                                    Context)(JSAny, JSAny);
   extern builtin IterableToListWithSymbolLookup(implicit context:
-                                                    Context)(Object);
+                                                    Context)(JSAny);
 }

src/builtins/math.tq

@@ -7,7 +7,7 @@ namespace math {
   extern macro Float64Acos(float64): float64;
 
   transitioning javascript builtin
-  MathAcos(context: Context, _receiver: Object, x: Object): Number {
+  MathAcos(context: Context, _receiver: JSAny, x: JSAny): Number {
     const value = Convert<float64>(ToNumber_Inline(context, x));
     return Convert<Number>(Float64Acos(value));
   }
@@ -16,7 +16,7 @@ namespace math {
   extern macro Float64Acosh(float64): float64;
 
   transitioning javascript builtin
-  MathAcosh(context: Context, _receiver: Object, x: Object): Number {
+  MathAcosh(context: Context, _receiver: JSAny, x: JSAny): Number {
     const value = Convert<float64>(ToNumber_Inline(context, x));
     return Convert<Number>(Float64Acosh(value));
   }
@@ -25,7 +25,7 @@ namespace math {
   extern macro Float64Asin(float64): float64;
 
   transitioning javascript builtin
-  MathAsin(context: Context, _receiver: Object, x: Object): Number {
+  MathAsin(context: Context, _receiver: JSAny, x: JSAny): Number {
     const value = Convert<float64>(ToNumber_Inline(context, x));
     return Convert<Number>(Float64Asin(value));
   }
@@ -34,7 +34,7 @@ namespace math {
   extern macro Float64Asinh(float64): float64;
 
   transitioning javascript builtin
-  MathAsinh(context: Context, _receiver: Object, x: Object): Number {
+  MathAsinh(context: Context, _receiver: JSAny, x: JSAny): Number {
     const value = Convert<float64>(ToNumber_Inline(context, x));
     return Convert<Number>(Float64Asinh(value));
   }
@@ -43,7 +43,7 @@ namespace math {
   extern macro Float64Atan(float64): float64;
 
   transitioning javascript builtin
-  MathAtan(context: Context, _receiver: Object, x: Object): Number {
+  MathAtan(context: Context, _receiver: JSAny, x: JSAny): Number {
     const value = Convert<float64>(ToNumber_Inline(context, x));
     return Convert<Number>(Float64Atan(value));
   }
@@ -52,7 +52,7 @@ namespace math {
   extern macro Float64Atan2(float64, float64): float64;
 
   transitioning javascript builtin
-  MathAtan2(context: Context, _receiver: Object, y: Object, x: Object): Number {
+  MathAtan2(context: Context, _receiver: JSAny, y: JSAny, x: JSAny): Number {
     const yValue = Convert<float64>(ToNumber_Inline(context, y));
     const xValue = Convert<float64>(ToNumber_Inline(context, x));
     return Convert<Number>(Float64Atan2(yValue, xValue));
@@ -62,7 +62,7 @@ namespace math {
   extern macro Float64Atanh(float64): float64;
 
   transitioning javascript builtin
-  MathAtanh(context: Context, _receiver: Object, x: Object): Number {
+  MathAtanh(context: Context, _receiver: JSAny, x: JSAny): Number {
     const value = Convert<float64>(ToNumber_Inline(context, x));
     return Convert<Number>(Float64Atanh(value));
   }
@@ -71,7 +71,7 @@ namespace math {
   extern macro Float64Cbrt(float64): float64;
 
   transitioning javascript builtin
-  MathCbrt(context: Context, _receiver: Object, x: Object): Number {
+  MathCbrt(context: Context, _receiver: JSAny, x: JSAny): Number {
     const value = Convert<float64>(ToNumber_Inline(context, x));
     return Convert<Number>(Float64Cbrt(value));
   }
@@ -80,7 +80,7 @@ namespace math {
   extern macro Word32Clz(int32): int32;
 
   transitioning javascript builtin
-  MathClz32(context: Context, _receiver: Object, x: Object): Number {
+  MathClz32(context: Context, _receiver: JSAny, x: JSAny): Number {
     const num = ToNumber_Inline(context, x);
 
     let value: int32;
@@ -100,7 +100,7 @@ namespace math {
   extern macro Float64Cos(float64): float64;
 
   transitioning javascript builtin
-  MathCos(context: Context, _receiver: Object, x: Object): Number {
+  MathCos(context: Context, _receiver: JSAny, x: JSAny): Number {
     const value = Convert<float64>(ToNumber_Inline(context, x));
     return Convert<Number>(Float64Cos(value));
   }
@@ -109,7 +109,7 @@ namespace math {
   extern macro Float64Cosh(float64): float64;
 
   transitioning javascript builtin
-  MathCosh(context: Context, _receiver: Object, x: Object): Number {
+  MathCosh(context: Context, _receiver: JSAny, x: JSAny): Number {
     const value = Convert<float64>(ToNumber_Inline(context, x));
     return Convert<Number>(Float64Cosh(value));
   }
@@ -118,7 +118,7 @@ namespace math {
   extern macro Float64Exp(float64): float64;
 
   transitioning javascript builtin
-  MathExp(context: Context, _receiver: Object, x: Object): Number {
+  MathExp(context: Context, _receiver: JSAny, x: JSAny): Number {
     const value = Convert<float64>(ToNumber_Inline(context, x));
     return Convert<Number>(Float64Exp(value));
   }
@@ -127,14 +127,14 @@ namespace math {
   extern macro Float64Expm1(float64): float64;
 
   transitioning javascript builtin
-  MathExpm1(context: Context, _receiver: Object, x: Object): Number {
+  MathExpm1(context: Context, _receiver: JSAny, x: JSAny): Number {
     const value = Convert<float64>(ToNumber_Inline(context, x));
     return Convert<Number>(Float64Expm1(value));
   }
 
   // ES6 #sec-math.fround
   transitioning javascript builtin
-  MathFround(context: Context, _receiver: Object, x: Object): Number {
+  MathFround(context: Context, _receiver: JSAny, x: JSAny): Number {
     const x32 = Convert<float32>(ToNumber_Inline(context, x));
     const x64 = Convert<float64>(x32);
     return Convert<Number>(x64);
@@ -144,7 +144,7 @@ namespace math {
   extern macro Float64Log(float64): float64;
 
   transitioning javascript builtin
-  MathLog(context: Context, _receiver: Object, x: Object): Number {
+  MathLog(context: Context, _receiver: JSAny, x: JSAny): Number {
     const value = Convert<float64>(ToNumber_Inline(context, x));
     return Convert<Number>(Float64Log(value));
   }
@@ -153,7 +153,7 @@ namespace math {
   extern macro Float64Log1p(float64): float64;
 
   transitioning javascript builtin
-  MathLog1p(context: Context, _receiver: Object, x: Object): Number {
+  MathLog1p(context: Context, _receiver: JSAny, x: JSAny): Number {
     const value = Convert<float64>(ToNumber_Inline(context, x));
     return Convert<Number>(Float64Log1p(value));
   }
@@ -162,7 +162,7 @@ namespace math {
   extern macro Float64Log10(float64): float64;
 
   transitioning javascript builtin
-  MathLog10(context: Context, _receiver: Object, x: Object): Number {
+  MathLog10(context: Context, _receiver: JSAny, x: JSAny): Number {
     const value = Convert<float64>(ToNumber_Inline(context, x));
     return Convert<Number>(Float64Log10(value));
   }
@@ -171,7 +171,7 @@ namespace math {
   extern macro Float64Log2(float64): float64;
 
   transitioning javascript builtin
-  MathLog2(context: Context, _receiver: Object, x: Object): Number {
+  MathLog2(context: Context, _receiver: JSAny, x: JSAny): Number {
     const value = Convert<float64>(ToNumber_Inline(context, x));
     return Convert<Number>(Float64Log2(value));
   }
@@ -180,14 +180,14 @@ namespace math {
   extern macro Float64Sin(float64): float64;
 
   transitioning javascript builtin
-  MathSin(context: Context, _receiver: Object, x: Object): Number {
+  MathSin(context: Context, _receiver: JSAny, x: JSAny): Number {
     const value = Convert<float64>(ToNumber_Inline(context, x));
     return Convert<Number>(Float64Sin(value));
   }
 
   // ES6 #sec-math.sign
   transitioning javascript builtin
-  MathSign(context: Context, _receiver: Object, x: Object): Number {
+  MathSign(context: Context, _receiver: JSAny, x: JSAny): Number {
     const num = ToNumber_Inline(context, x);
     const value = Convert<float64>(num);
 
@@ -204,7 +204,7 @@ namespace math {
   extern macro Float64Sinh(float64): float64;
 
   transitioning javascript builtin
-  MathSinh(context: Context, _receiver: Object, x: Object): Number {
+  MathSinh(context: Context, _receiver: JSAny, x: JSAny): Number {
     const value = Convert<float64>(ToNumber_Inline(context, x));
     return Convert<Number>(Float64Sinh(value));
   }
@@ -213,7 +213,7 @@ namespace math {
   extern macro Float64Sqrt(float64): float64;
 
   transitioning javascript builtin
-  MathSqrt(context: Context, _receiver: Object, x: Object): Number {
+  MathSqrt(context: Context, _receiver: JSAny, x: JSAny): Number {
     const value = Convert<float64>(ToNumber_Inline(context, x));
     return Convert<Number>(Float64Sqrt(value));
   }
@@ -222,7 +222,7 @@ namespace math {
   extern macro Float64Tan(float64): float64;
 
   transitioning javascript builtin
-  MathTan(context: Context, _receiver: Object, x: Object): Number {
+  MathTan(context: Context, _receiver: JSAny, x: JSAny): Number {
     const value = Convert<float64>(ToNumber_Inline(context, x));
     return Convert<Number>(Float64Tan(value));
   }
@@ -231,7 +231,7 @@ namespace math {
   extern macro Float64Tanh(float64): float64;
 
   transitioning javascript builtin
-  MathTanh(context: Context, _receiver: Object, x: Object): Number {
+  MathTanh(context: Context, _receiver: JSAny, x: JSAny): Number {
     const value = Convert<float64>(ToNumber_Inline(context, x));
     return Convert<Number>(Float64Tanh(value));
   }
@@ -240,7 +240,7 @@ namespace math {
 
   // ES6 #sec-math.hypot
   transitioning javascript builtin
-  MathHypot(js-implicit context: Context, receiver: Object)(...arguments):
+  MathHypot(js-implicit context: Context, receiver: JSAny)(...arguments):
       Number {
     const length = arguments.length;
     if (length == 0) {

src/builtins/object-fromentries.tq

@@ -5,7 +5,7 @@
 namespace object {
 
   transitioning macro ObjectFromEntriesFastCase(implicit context: Context)(
-      iterable: Object): JSObject labels IfSlow {
+      iterable: JSAny): JSObject labels IfSlow {
     typeswitch (iterable) {
       case (array: FastJSArrayWithNoCustomIteration): {
         const elements: FixedArray =
@@ -14,7 +14,7 @@ namespace object {
         const result: JSObject = NewJSObject();
 
         for (let k: Smi = 0; k < length; ++k) {
-          const value: Object = array::LoadElementOrUndefined(elements, k);
+          const value: JSAny = array::LoadElementOrUndefined(elements, k);
           const pair: KeyValuePair =
               collections::LoadKeyValuePairNoSideEffects(value)
               otherwise IfSlow;
@@ -26,16 +26,16 @@ namespace object {
         }
         return result;
       }
-      case (Object): {
+      case (JSAny): {
         goto IfSlow;
       }
     }
   }
 
   transitioning javascript builtin
-  ObjectFromEntries(js-implicit context: Context, receiver: Object)(
-      ...arguments): Object {
-    const iterable: Object = arguments[0];
+  ObjectFromEntries(js-implicit context: Context, receiver: JSAny)(
+      ...arguments): JSAny {
+    const iterable: JSAny = arguments[0];
     try {
       if (IsNullOrUndefined(iterable)) goto Throw;
       return ObjectFromEntriesFastCase(iterable) otherwise IfSlow;
@@ -50,7 +50,7 @@ namespace object {
           const step: JSReceiver =
               iterator::IteratorStep(i, fastIteratorResultMap)
               otherwise return result;
-          const iteratorValue: Object =
+          const iteratorValue: JSAny =
               iterator::IteratorValue(step, fastIteratorResultMap);
           const pair: KeyValuePair =
               collections::LoadKeyValuePair(iteratorValue);

src/builtins/object.tq

@@ -4,31 +4,31 @@
 
 namespace runtime {
   extern transitioning runtime
-  ObjectIsExtensible(implicit context: Context)(Object): Object;
+  ObjectIsExtensible(implicit context: Context)(JSAny): JSAny;
 
   extern transitioning runtime
   JSReceiverPreventExtensionsThrow(implicit context: Context)(JSReceiver):
-      Object;
+      JSAny;
 
   extern transitioning runtime
   JSReceiverPreventExtensionsDontThrow(implicit context: Context)(JSReceiver):
-      Object;
+      JSAny;
 
   extern transitioning runtime
-  JSReceiverGetPrototypeOf(implicit context: Context)(JSReceiver): Object;
+  JSReceiverGetPrototypeOf(implicit context: Context)(JSReceiver): JSAny;
 
   extern transitioning runtime
-  JSReceiverSetPrototypeOfThrow(implicit context: Context)(JSReceiver, Object):
-      Object;
+  JSReceiverSetPrototypeOfThrow(implicit context: Context)(JSReceiver, JSAny):
+      JSAny;
 
   extern transitioning runtime
   JSReceiverSetPrototypeOfDontThrow(implicit context:
-                                        Context)(JSReceiver, Object): Object;
+                                        Context)(JSReceiver, JSAny): JSAny;
 }  // namespace runtime
 
 namespace object {
   transitioning macro
-  ObjectIsExtensible(implicit context: Context)(object: Object): Object {
+  ObjectIsExtensible(implicit context: Context)(object: JSAny): JSAny {
     const objectJSReceiver = Cast<JSReceiver>(object) otherwise return False;
     const objectJSProxy = Cast<JSProxy>(objectJSReceiver)
         otherwise return runtime::ObjectIsExtensible(objectJSReceiver);
@@ -36,8 +36,8 @@ namespace object {
   }
 
   transitioning macro
-  ObjectPreventExtensionsThrow(implicit context: Context)(object: Object):
-      Object {
+  ObjectPreventExtensionsThrow(implicit context: Context)(object: JSAny):
+      JSAny {
     const objectJSReceiver = Cast<JSReceiver>(object) otherwise return object;
     const objectJSProxy = Cast<JSProxy>(objectJSReceiver)
         otherwise return runtime::JSReceiverPreventExtensionsThrow(
@@ -47,8 +47,8 @@ namespace object {
   }
 
   transitioning macro
-  ObjectPreventExtensionsDontThrow(implicit context: Context)(object: Object):
-      Object {
+  ObjectPreventExtensionsDontThrow(implicit context: Context)(object: JSAny):
+      JSAny {
     const objectJSReceiver = Cast<JSReceiver>(object) otherwise return False;
     const objectJSProxy = Cast<JSProxy>(objectJSReceiver)
         otherwise return runtime::JSReceiverPreventExtensionsDontThrow(
@@ -57,14 +57,14 @@ namespace object {
   }
 
   transitioning macro
-  ObjectGetPrototypeOf(implicit context: Context)(object: Object): Object {
+  ObjectGetPrototypeOf(implicit context: Context)(object: JSAny): JSAny {
     const objectJSReceiver: JSReceiver = ToObject_Inline(context, object);
     return object::JSReceiverGetPrototypeOf(objectJSReceiver);
   }
 
   transitioning macro
   JSReceiverGetPrototypeOf(implicit context: Context)(object: JSReceiver):
-      Object {
+      JSAny {
     const objectJSProxy = Cast<JSProxy>(object)
         otherwise return runtime::JSReceiverGetPrototypeOf(object);
     return proxy::ProxyGetPrototypeOf(objectJSProxy);
@@ -72,7 +72,7 @@ namespace object {
 
   transitioning macro
   ObjectSetPrototypeOfThrow(implicit context: Context)(
-      object: Object, proto: Object): Object {
+      object: JSAny, proto: JSReceiver | Null): JSAny {
     const objectJSReceiver = Cast<JSReceiver>(object) otherwise return object;
     const objectJSProxy = Cast<JSProxy>(objectJSReceiver)
         otherwise return runtime::JSReceiverSetPrototypeOfThrow(
@@ -83,7 +83,7 @@ namespace object {
 
   transitioning macro
   ObjectSetPrototypeOfDontThrow(implicit context: Context)(
-      object: Object, proto: Object): Object {
+      object: JSAny, proto: JSReceiver | Null): JSAny {
     const objectJSReceiver = Cast<JSReceiver>(object) otherwise return False;
     const objectJSProxy = Cast<JSProxy>(objectJSReceiver)
         otherwise return runtime::JSReceiverSetPrototypeOfDontThrow(
@@ -95,7 +95,7 @@ namespace object {
 namespace object_isextensible {
   // ES6 section 19.1.2.11 Object.isExtensible ( O )
   transitioning javascript builtin ObjectIsExtensible(
-      js-implicit context: Context)(_receiver: Object, object: Object): Object {
+      js-implicit context: Context)(_receiver: JSAny, object: JSAny): JSAny {
     return object::ObjectIsExtensible(object);
   }
 }  // namespace object_isextensible
@@ -103,7 +103,7 @@ namespace object_isextensible {
 namespace object_preventextensions {
   // ES6 section 19.1.2.11 Object.isExtensible ( O )
   transitioning javascript builtin ObjectPreventExtensions(
-      js-implicit context: Context)(_receiver: Object, object: Object): Object {
+      js-implicit context: Context)(_receiver: JSAny, object: JSAny): JSAny {
     return object::ObjectPreventExtensionsThrow(object);
   }
 }  // namespace object_preventextensions
@@ -111,7 +111,7 @@ namespace object_preventextensions {
 namespace object_getprototypeof {
   // ES6 section 19.1.2.9 Object.getPrototypeOf ( O )
   transitioning javascript builtin ObjectGetPrototypeOf(
-      js-implicit context: Context)(_receiver: Object, object: Object): Object {
+      js-implicit context: Context)(_receiver: JSAny, object: JSAny): JSAny {
     return object::ObjectGetPrototypeOf(object);
   }
 }  // namespace object_getprototypeof
@@ -120,7 +120,7 @@ namespace object_setprototypeof {
   // ES6 section 19.1.2.21 Object.setPrototypeOf ( O, proto )
   transitioning javascript builtin ObjectSetPrototypeOf(
       js-implicit context:
-          Context)(_receiver: Object, object: Object, proto: Object): Object {
+          Context)(_receiver: JSAny, object: JSAny, proto: JSAny): JSAny {
     // 1. Set O to ? RequireObjectCoercible(O).
     RequireObjectCoercible(object, 'Object.setPrototypeOf');
 
@@ -130,9 +130,13 @@ namespace object_setprototypeof {
     // 4. Let status be ? O.[[SetPrototypeOf]](proto).
     // 5. If status is false, throw a TypeError exception.
     // 6. Return O.
-    if (proto == Null || Is<JSReceiver>(proto)) {
-      return object::ObjectSetPrototypeOfThrow(object, proto);
+    typeswitch (proto) {
+      case (proto: JSReceiver | Null): {
+        return object::ObjectSetPrototypeOfThrow(object, proto);
+      }
+      case (JSAny): {
+        ThrowTypeError(kProtoObjectOrNull, proto);
+      }
     }
-    ThrowTypeError(kProtoObjectOrNull, proto);
   }
 }  // namespace object_setprototypeof

src/builtins/proxy-constructor.tq

@@ -10,8 +10,8 @@ namespace proxy {
   // https://tc39.github.io/ecma262/#sec-proxy-constructor
   transitioning javascript builtin
   ProxyConstructor(
-      js-implicit context: Context, receiver: Object,
-      newTarget: Object)(target: Object, handler: Object): JSProxy {
+      js-implicit context: Context, receiver: JSAny,
+      newTarget: JSAny)(target: JSAny, handler: JSAny): JSProxy {
     try {
       // 1. If NewTarget is undefined, throw a TypeError exception.
       if (newTarget == Undefined) {

src/builtins/proxy-delete-property.tq

@@ -10,7 +10,7 @@ namespace proxy {
   // https://tc39.es/ecma262/#sec-proxy-object-internal-methods-and-internal-slots-delete-p
   transitioning builtin
   ProxyDeleteProperty(implicit context: Context)(
-      proxy: JSProxy, name: Name, languageMode: LanguageMode): Object {
+      proxy: JSProxy, name: PropertyKey, languageMode: LanguageMode): JSAny {
     const kTrapName: constexpr string = 'deleteProperty';
     // Handle deeply nested proxy.
     PerformStackCheck();
@@ -58,7 +58,7 @@ namespace proxy {
       // 15. Return true.
       return True;
     }
-    label TrapUndefined(target: Object) {
+    label TrapUndefined(target: JSAny) {
       // 7.a. Return ? target.[[Delete]](P).
       return DeleteProperty(target, name, languageMode);
     }

src/builtins/proxy-get-property.tq

@@ -7,14 +7,14 @@
 namespace proxy {
 
   extern transitioning builtin GetPropertyWithReceiver(
-      implicit context: Context)(Object, Name, Object, Smi): Object;
+      implicit context: Context)(JSAny, Name, JSAny, Smi): JSAny;
 
   // ES #sec-proxy-object-internal-methods-and-internal-slots-get-p-receiver
   // https://tc39.github.io/ecma262/#sec-proxy-object-internal-methods-and-internal-slots-get-p-receiver
   transitioning builtin
   ProxyGetProperty(implicit context: Context)(
-      proxy: JSProxy, name: Name, receiverValue: Object,
-      onNonExistent: Smi): Object {
+      proxy: JSProxy, name: PropertyKey, receiverValue: JSAny,
+      onNonExistent: Smi): JSAny {
     PerformStackCheck();
     // 1. Assert: IsPropertyKey(P) is true.
     assert(TaggedIsNotSmi(name));

src/builtins/proxy-get-prototype-of.tq

@@ -9,7 +9,7 @@ namespace proxy {
   // ES #sec-proxy-object-internal-methods-and-internal-slots-isextensible
   // https://tc39.github.io/ecma262/#sec-proxy-object-internal-methods-and-internal-slots-isextensible
   transitioning builtin
-  ProxyGetPrototypeOf(implicit context: Context)(proxy: JSProxy): Object {
+  ProxyGetPrototypeOf(implicit context: Context)(proxy: JSProxy): JSAny {
     PerformStackCheck();
     const kTrapName: constexpr string = 'getPrototypeOf';
     try {
@@ -39,7 +39,7 @@ namespace proxy {
 
       // 9. Let extensibleTarget be ? IsExtensible(target).
       // 10. If extensibleTarget is true, return handlerProto.
-      const extensibleTarget: Object = object::ObjectIsExtensible(target);
+      const extensibleTarget: JSAny = object::ObjectIsExtensible(target);
       assert(extensibleTarget == True || extensibleTarget == False);
       if (extensibleTarget == True) {
         return handlerProto;
@@ -56,7 +56,7 @@ namespace proxy {
       }
       ThrowTypeError(kProxyGetPrototypeOfNonExtensible);
     }
-    label TrapUndefined(target: Object) {
+    label TrapUndefined(target: JSAny) {
       // 6.a. Return ? target.[[GetPrototypeOf]]().
       return object::ObjectGetPrototypeOf(target);
     }

src/builtins/proxy-has-property.tq

@@ -9,7 +9,7 @@ namespace proxy {
   // ES #sec-proxy-object-internal-methods-and-internal-slots-hasproperty-p
   // https://tc39.github.io/ecma262/#sec-proxy-object-internal-methods-and-internal-slots-hasproperty-p
   transitioning builtin ProxyHasProperty(implicit context: Context)(
-      proxy: JSProxy, name: Name): Object {
+      proxy: JSProxy, name: PropertyKey): JSAny {
     assert(IsJSProxy(proxy));
 
     PerformStackCheck();
@@ -46,7 +46,7 @@ namespace proxy {
       CheckHasTrapResult(target, proxy, name);
       return False;
     }
-    label TrapUndefined(target: Object) {
+    label TrapUndefined(target: JSAny) {
       // 7.a. Return ? target.[[HasProperty]](P).
       tail HasProperty(target, name);
     }

src/builtins/proxy-is-extensible.tq

@@ -9,7 +9,7 @@ namespace proxy {
   // ES #sec-proxy-object-internal-methods-and-internal-slots-isextensible
   // https://tc39.github.io/ecma262/#sec-proxy-object-internal-methods-and-internal-slots-isextensible
   transitioning builtin ProxyIsExtensible(implicit context:
-                                              Context)(proxy: JSProxy): Object {
+                                              Context)(proxy: JSProxy): JSAny {
     PerformStackCheck();
     const kTrapName: constexpr string = 'isExtensible';
     try {
@@ -45,7 +45,7 @@ namespace proxy {
       // 10. Return booleanTrapResult.
       return SelectBooleanConstant(trapResult);
     }
-    label TrapUndefined(target: Object) {
+    label TrapUndefined(target: JSAny) {
       // 6.a. Return ? IsExtensible(target).
       return object::ObjectIsExtensible(target);
     }

src/builtins/proxy-prevent-extensions.tq

@@ -9,8 +9,8 @@ namespace proxy {
   // ES #sec-proxy-object-internal-methods-and-internal-slots-preventextensions
   // https://tc39.es/ecma262/#sec-proxy-object-internal-methods-and-internal-slots-preventextensions
   transitioning builtin
-  ProxyPreventExtensions(implicit context: Context)(
-      proxy: JSProxy, doThrow: Boolean): Object {
+  ProxyPreventExtensions(implicit context:
+                             Context)(proxy: JSProxy, doThrow: Boolean): JSAny {
     PerformStackCheck();
     const kTrapName: constexpr string = 'preventExtensions';
     try {
@@ -37,7 +37,7 @@ namespace proxy {
       //    8.a. Let extensibleTarget be ? IsExtensible(target).
       //    8.b If extensibleTarget is true, throw a TypeError exception.
       if (ToBoolean(trapResult)) {
-        const extensibleTarget: Object = object::ObjectIsExtensible(target);
+        const extensibleTarget: JSAny = object::ObjectIsExtensible(target);
         assert(extensibleTarget == True || extensibleTarget == False);
         if (extensibleTarget == True) {
           ThrowTypeError(kProxyPreventExtensionsExtensible);
@@ -52,7 +52,7 @@ namespace proxy {
       // 9. Return booleanTrapResult.
       return True;
     }
-    label TrapUndefined(target: Object) {
+    label TrapUndefined(target: JSAny) {
       // 6.a. Return ? target.[[PreventExtensions]]().
       if (doThrow == True) {
         return object::ObjectPreventExtensionsThrow(target);

src/builtins/proxy-revocable.tq

@@ -12,9 +12,8 @@ namespace proxy {
   // Proxy.revocable(target, handler)
   // https://tc39.github.io/ecma262/#sec-proxy.revocable
   transitioning javascript builtin
-  ProxyRevocable(
-      context: Context, _receiver: Object, target: Object,
-      handler: Object): JSProxyRevocableResult {
+  ProxyRevocable(js-implicit context: Context)(
+      _receiver: JSAny, target: JSAny, handler: JSAny): JSProxyRevocableResult {
     try {
       const targetJSReceiver =
           Cast<JSReceiver>(target) otherwise ThrowProxyNonObject;

src/builtins/proxy-set-property.tq

@@ -19,15 +19,21 @@ namespace proxy {
   // https://tc39.github.io/ecma262/#sec-proxy-object-internal-methods-and-internal-slots-set-p-v-receiver
   transitioning builtin
   ProxySetProperty(implicit context: Context)(
-      proxy: JSProxy, name: Name, value: Object,
-      receiverValue: Object): Object {
+      proxy: JSProxy, name: PropertyKey | PrivateSymbol, value: JSAny,
+      receiverValue: JSAny): JSAny {
     // 1. Assert: IsPropertyKey(P) is true.
     assert(TaggedIsNotSmi(name));
     assert(IsName(name));
 
-    if (IsPrivateSymbol(name)) {
-      CallThrowTypeErrorIfStrict(kProxyPrivate);
-      return Undefined;
+    let key: PropertyKey;
+    typeswitch (name) {
+      case (PrivateSymbol): {
+        CallThrowTypeErrorIfStrict(kProxyPrivate);
+        return Undefined;
+      }
+      case (name: PropertyKey): {
+        key = name;
+      }
     }
 
     try {
@@ -61,7 +67,7 @@ namespace proxy {
       //      exception.
       // 12. Return true.
       const trapResult =
-          Call(context, trap, handler, target, name, value, receiverValue);
+          Call(context, trap, handler, target, key, value, receiverValue);
       if (ToBoolean(trapResult)) {
         CheckGetSetTrapResult(target, proxy, name, value, kProxySet);
         return value;

src/builtins/proxy-set-prototype-of.tq

@@ -10,7 +10,7 @@ namespace proxy {
   // https://tc39.es/ecma262/#sec-proxy-object-internal-methods-and-internal-slots-setprototypeof-v
   transitioning builtin
   ProxySetPrototypeOf(implicit context: Context)(
-      proxy: JSProxy, proto: Object, doThrow: Boolean): Object {
+      proxy: JSProxy, proto: Null | JSReceiver, doThrow: Boolean): JSAny {
     PerformStackCheck();
     const kTrapName: constexpr string = 'setPrototypeOf';
     try {
@@ -63,7 +63,7 @@ namespace proxy {
       }
       ThrowTypeError(kProxySetPrototypeOfNonExtensible);
     }
-    label TrapUndefined(target: Object, proto: Object) {
+    label TrapUndefined(target: JSAny, proto: JSReceiver | Null) {
       // 7.a. Return ? target.[[SetPrototypeOf]]().
       if (doThrow == True) {
         return object::ObjectSetPrototypeOfThrow(target, proto);

src/builtins/reflect.tq

@@ -9,7 +9,7 @@ namespace reflect {
 
   // ES6 section 26.1.10 Reflect.isExtensible
   transitioning javascript builtin ReflectIsExtensible(
-      js-implicit context: Context)(_receiver: Object, object: Object): Object {
+      js-implicit context: Context)(_receiver: JSAny, object: Object): Object {
     const objectJSReceiver = Cast<JSReceiver>(object)
         otherwise ThrowTypeError(kCalledOnNonObject, 'Reflect.isExtensible');
     return object::ObjectIsExtensible(objectJSReceiver);
@@ -17,7 +17,7 @@ namespace reflect {
 
   // ES6 section 26.1.12 Reflect.preventExtensions
   transitioning javascript builtin ReflectPreventExtensions(
-      js-implicit context: Context)(_receiver: Object, object: Object): Object {
+      js-implicit context: Context)(_receiver: JSAny, object: Object): Object {
     const objectJSReceiver = Cast<JSReceiver>(object)
         otherwise ThrowTypeError(kCalledOnNonObject, 'Reflect.preventExtensions');
     return object::ObjectPreventExtensionsDontThrow(objectJSReceiver);
@@ -25,7 +25,7 @@ namespace reflect {
 
   // ES6 section 26.1.8 Reflect.getPrototypeOf
   transitioning javascript builtin ReflectGetPrototypeOf(
-      js-implicit context: Context)(_receiver: Object, object: Object): Object {
+      js-implicit context: Context)(_receiver: JSAny, object: Object): Object {
     const objectJSReceiver = Cast<JSReceiver>(object)
         otherwise ThrowTypeError(kCalledOnNonObject, 'Reflect.getPrototypeOf');
     return object::JSReceiverGetPrototypeOf(objectJSReceiver);
@@ -34,16 +34,21 @@ namespace reflect {
   // ES6 section 26.1.14 Reflect.setPrototypeOf
   transitioning javascript builtin ReflectSetPrototypeOf(
       js-implicit context:
-          Context)(_receiver: Object, object: Object, proto: Object): Object {
+          Context)(_receiver: JSAny, object: JSAny, proto: JSAny): JSAny {
     const objectJSReceiver = Cast<JSReceiver>(object)
         otherwise ThrowTypeError(kCalledOnNonObject, 'Reflect.setPrototypeOf');
-    if (proto == Null || Is<JSReceiver>(proto)) {
-      return object::ObjectSetPrototypeOfDontThrow(objectJSReceiver, proto);
+    typeswitch (proto) {
+      case (proto: JSReceiver | Null): {
+        return object::ObjectSetPrototypeOfDontThrow(objectJSReceiver, proto);
+      }
+      case (JSAny): {
+        ThrowTypeError(kProtoObjectOrNull, proto);
+      }
     }
-    ThrowTypeError(kProtoObjectOrNull, proto);
   }
 
-  extern transitioning builtin ToName(implicit context: Context)(Object): Name;
+  extern transitioning builtin ToName(implicit context: Context)(Object):
+      AnyName;
   type OnNonExistent constexpr 'OnNonExistent';
   const kReturnUndefined: constexpr OnNonExistent
   generates 'OnNonExistent::kReturnUndefined';
@@ -59,8 +64,8 @@ namespace reflect {
     const objectJSReceiver = Cast<JSReceiver>(object)
         otherwise ThrowTypeError(kCalledOnNonObject, 'Reflect.get');
     const propertyKey: Object = length > 1 ? arguments[1] : Undefined;
-    const name: Name = ToName(propertyKey);
-    const receiver: Object = length > 2 ? arguments[2] : objectJSReceiver;
+    const name: AnyName = ToName(propertyKey);
+    const receiver: JSAny = length > 2 ? arguments[2] : objectJSReceiver;
     return GetPropertyWithReceiver(
         objectJSReceiver, name, receiver, SmiConstant(kReturnUndefined));
   }
@@ -68,7 +73,7 @@ namespace reflect {
   // ES6 section 26.1.4 Reflect.deleteProperty
   transitioning javascript builtin ReflectDeleteProperty(
       js-implicit context:
-          Context)(_receiver: Object, object: Object, key: Object): Object {
+          Context)(_receiver: JSAny, object: JSAny, key: JSAny): JSAny {
     const objectJSReceiver = Cast<JSReceiver>(object)
         otherwise ThrowTypeError(kCalledOnNonObject, 'Reflect.deleteProperty');
     return DeleteProperty(objectJSReceiver, key, kSloppy);

src/builtins/regexp-replace.tq

@@ -57,7 +57,7 @@ namespace regexp_replace {
         // Element represents the matched substring, which is then passed to the
         // replace function.
         case (elString: String): {
-          const replacementObj: Object =
+          const replacementObj: JSAny =
               Call(context, replaceFn, Undefined, elString, matchStart, string);
           const replacement: String = ToString_Inline(context, replacementObj);
           matchesElements.objects[i] = replacement;
@@ -79,7 +79,7 @@ namespace regexp_replace {
 
       // The JSArray is expanded into the function args by Reflect.apply().
       // TODO(jgruber): Remove indirection through Call->ReflectApply.
-      const replacementObj: Object = Call(
+      const replacementObj: JSAny = Call(
           context, GetReflectApply(), Undefined, replaceFn, Undefined, elArray);
 
       // Overwrite the i'th element in the results with the string
@@ -172,7 +172,7 @@ namespace regexp_replace {
   }
 
   transitioning builtin RegExpReplace(implicit context: Context)(
-      regexp: FastJSRegExp, string: String, replaceValue: Object): String {
+      regexp: FastJSRegExp, string: String, replaceValue: JSAny): String {
     // TODO(pwong): Remove assert when all callers (StringPrototypeReplace) are
     // from Torque.
     assert(Is<FastJSRegExp>(regexp));
@@ -184,7 +184,7 @@ namespace regexp_replace {
             RegExpReplaceFastGlobalCallable(regexp, string, replaceFn) :
             StringReplaceNonGlobalRegExpWithFunction(string, regexp, replaceFn);
       }
-      case (Object): {
+      case (JSAny): {
         const stableRegexp: JSRegExp = regexp;
         const replaceString: String = ToString_Inline(context, replaceValue);
 
@@ -208,7 +208,7 @@ namespace regexp_replace {
   }
 
   transitioning javascript builtin RegExpPrototypeReplace(
-      js-implicit context: Context, receiver: Object)(...arguments): Object {
+      js-implicit context: Context, receiver: JSAny)(...arguments): Object {
     const methodName: constexpr string = 'RegExp.prototype.@@replace';
 
     // RegExpPrototypeReplace is a bit of a beast - a summary of dispatch logic:
@@ -229,8 +229,8 @@ namespace regexp_replace {
     //   }
     // }
 
-    const string: Object = arguments[0];
-    const replaceValue: Object = arguments[1];
+    const string: JSAny = arguments[0];
+    const replaceValue: JSAny = arguments[1];
 
     // Let rx be the this value.
     // If Type(rx) is not Object, throw a TypeError exception.

src/builtins/string-endswith.tq

@@ -28,13 +28,13 @@ namespace string {
 
   // https://tc39.github.io/ecma262/#sec-string.prototype.endswith
   transitioning javascript builtin StringPrototypeEndsWith(
-      js-implicit context: Context, receiver: Object)(...arguments): Boolean {
-    const searchString: Object = arguments[0];
-    const endPosition: Object = arguments[1];
+      js-implicit context: Context, receiver: JSAny)(...arguments): Boolean {
+    const searchString: JSAny = arguments[0];
+    const endPosition: JSAny = arguments[1];
     const kBuiltinName: constexpr string = 'String.prototype.endsWith';
 
     // 1. Let O be ? RequireObjectCoercible(this value).
-    const object: Object = RequireObjectCoercible(receiver, kBuiltinName);
+    const object: JSAny = RequireObjectCoercible(receiver, kBuiltinName);
 
     // 2. Let S be ? ToString(O).
     const string: String = ToString_Inline(context, object);

src/builtins/string-html.tq

@@ -7,8 +7,8 @@ namespace string_html {
 
   // https://tc39.github.io/ecma262/#sec-createhtml
   transitioning builtin CreateHTML(implicit context: Context)(
-      receiver: Object, methodName: String, tagName: String, attr: String,
-      attrValue: Object): String {
+      receiver: JSAny, methodName: String, tagName: String, attr: String,
+      attrValue: JSAny): String {
     const tagContents: String = ToThisString(receiver, methodName);
     let result = '<' + tagName;
     if (attr != kEmptyString) {
@@ -22,14 +22,14 @@ namespace string_html {
 
   // https://tc39.github.io/ecma262/#sec-string.prototype.anchor
   transitioning javascript builtin StringPrototypeAnchor(
-      js-implicit context: Context, receiver: Object)(...arguments): String {
+      js-implicit context: Context, receiver: JSAny)(...arguments): String {
     return CreateHTML(
         receiver, 'String.prototype.anchor', 'a', 'name', arguments[0]);
   }
 
   // https://tc39.github.io/ecma262/#sec-string.prototype.big
   transitioning javascript builtin
-  StringPrototypeBig(js-implicit context: Context, receiver: Object)(
+  StringPrototypeBig(js-implicit context: Context, receiver: JSAny)(
       ...arguments): String {
     return CreateHTML(
         receiver, 'String.prototype.big', 'big', kEmptyString, kEmptyString);
@@ -37,7 +37,7 @@ namespace string_html {
 
   // https://tc39.github.io/ecma262/#sec-string.prototype.blink
   transitioning javascript builtin
-  StringPrototypeBlink(js-implicit context: Context, receiver: Object)(
+  StringPrototypeBlink(js-implicit context: Context, receiver: JSAny)(
       ...arguments): String {
     return CreateHTML(
         receiver, 'String.prototype.blink', 'blink', kEmptyString,
@@ -46,7 +46,7 @@ namespace string_html {
 
   // https://tc39.github.io/ecma262/#sec-string.prototype.bold
   transitioning javascript builtin
-  StringPrototypeBold(js-implicit context: Context, receiver: Object)(
+  StringPrototypeBold(js-implicit context: Context, receiver: JSAny)(
       ...arguments): String {
     return CreateHTML(
         receiver, 'String.prototype.bold', 'b', kEmptyString, kEmptyString);
@@ -54,7 +54,7 @@ namespace string_html {
 
   // https://tc39.github.io/ecma262/#sec-string.prototype.fontcolor
   transitioning javascript builtin
-  StringPrototypeFontcolor(js-implicit context: Context, receiver: Object)(
+  StringPrototypeFontcolor(js-implicit context: Context, receiver: JSAny)(
       ...arguments): String {
     return CreateHTML(
         receiver, 'String.prototype.fontcolor', 'font', 'color', arguments[0]);
@@ -62,7 +62,7 @@ namespace string_html {
 
   // https://tc39.github.io/ecma262/#sec-string.prototype.fontsize
   transitioning javascript builtin
-  StringPrototypeFontsize(js-implicit context: Context, receiver: Object)(
+  StringPrototypeFontsize(js-implicit context: Context, receiver: JSAny)(
       ...arguments): String {
     return CreateHTML(
         receiver, 'String.prototype.fontsize', 'font', 'size', arguments[0]);
@@ -70,7 +70,7 @@ namespace string_html {
 
   // https://tc39.github.io/ecma262/#sec-string.prototype.fixed
   transitioning javascript builtin
-  StringPrototypeFixed(js-implicit context: Context, receiver: Object)(
+  StringPrototypeFixed(js-implicit context: Context, receiver: JSAny)(
       ...arguments): String {
     return CreateHTML(
         receiver, 'String.prototype.fixed', 'tt', kEmptyString, kEmptyString);
@@ -78,7 +78,7 @@ namespace string_html {
 
   // https://tc39.github.io/ecma262/#sec-string.prototype.italics
   transitioning javascript builtin
-  StringPrototypeItalics(js-implicit context: Context, receiver: Object)(
+  StringPrototypeItalics(js-implicit context: Context, receiver: JSAny)(
       ...arguments): String {
     return CreateHTML(
         receiver, 'String.prototype.italics', 'i', kEmptyString, kEmptyString);
@@ -86,7 +86,7 @@ namespace string_html {
 
   // https://tc39.github.io/ecma262/#sec-string.prototype.link
   transitioning javascript builtin
-  StringPrototypeLink(js-implicit context: Context, receiver: Object)(
+  StringPrototypeLink(js-implicit context: Context, receiver: JSAny)(
       ...arguments): String {
     return CreateHTML(
         receiver, 'String.prototype.link', 'a', 'href', arguments[0]);
@@ -94,7 +94,7 @@ namespace string_html {
 
   // https://tc39.github.io/ecma262/#sec-string.prototype.small
   transitioning javascript builtin
-  StringPrototypeSmall(js-implicit context: Context, receiver: Object)(
+  StringPrototypeSmall(js-implicit context: Context, receiver: JSAny)(
       ...arguments): String {
     return CreateHTML(
         receiver, 'String.prototype.small', 'small', kEmptyString,
@@ -103,7 +103,7 @@ namespace string_html {
 
   // https://tc39.github.io/ecma262/#sec-string.prototype.strike
   transitioning javascript builtin
-  StringPrototypeStrike(js-implicit context: Context, receiver: Object)(
+  StringPrototypeStrike(js-implicit context: Context, receiver: JSAny)(
       ...arguments): String {
     return CreateHTML(
         receiver, 'String.prototype.strike', 'strike', kEmptyString,
@@ -112,7 +112,7 @@ namespace string_html {
 
   // https://tc39.github.io/ecma262/#sec-string.prototype.sub
   transitioning javascript builtin
-  StringPrototypeSub(js-implicit context: Context, receiver: Object)(
+  StringPrototypeSub(js-implicit context: Context, receiver: JSAny)(
       ...arguments): String {
     return CreateHTML(
         receiver, 'String.prototype.sub', 'sub', kEmptyString, kEmptyString);
@@ -120,7 +120,7 @@ namespace string_html {
 
   // https://tc39.github.io/ecma262/#sec-string.prototype.sup
   transitioning javascript builtin
-  StringPrototypeSup(js-implicit context: Context, receiver: Object)(
+  StringPrototypeSup(js-implicit context: Context, receiver: JSAny)(
       ...arguments): String {
     return CreateHTML(
         receiver, 'String.prototype.sup', 'sup', kEmptyString, kEmptyString);

src/builtins/string-iterator.tq

@@ -17,7 +17,7 @@ namespace string_iterator {
 
   // ES6 #sec-string.prototype-@@iterator
   transitioning javascript builtin StringPrototypeIterator(
-      js-implicit context: Context)(receiver: Object): JSStringIterator {
+      js-implicit context: Context)(receiver: JSAny): JSStringIterator {
     const name: String =
         ToThisString(receiver, 'String.prototype[Symbol.iterator]');
     const index: Smi = 0;
@@ -26,7 +26,7 @@ namespace string_iterator {
 
   // ES6 #sec-%stringiteratorprototype%.next
   transitioning javascript builtin StringIteratorPrototypeNext(
-      js-implicit context: Context)(receiver: Object): JSObject {
+      js-implicit context: Context)(receiver: JSAny): JSObject {
     const iterator = Cast<JSStringIterator>(receiver) otherwise ThrowTypeError(
         kIncompatibleMethodReceiver, 'String Iterator.prototype.next',
         receiver);

src/builtins/string-repeat.tq

@@ -28,7 +28,7 @@ namespace string_repeat {
 
   // https://tc39.github.io/ecma262/#sec-string.prototype.repeat
   transitioning javascript builtin StringPrototypeRepeat(
-      js-implicit context: Context, receiver: Object)(count: Object): String {
+      js-implicit context: Context, receiver: JSAny)(count: JSAny): String {
     // 1. Let O be ? RequireObjectCoercible(this value).
     // 2. Let S be ? ToString(O).
     const s: String = ToThisString(receiver, kBuiltinName);

src/builtins/string-slice.tq

@@ -9,7 +9,7 @@ namespace string_slice {
   // ES6 #sec-string.prototype.slice ( start, end )
   // https://tc39.github.io/ecma262/#sec-string.prototype.slice
   transitioning javascript builtin StringPrototypeSlice(
-      js-implicit context: Context, receiver: Object)(...arguments): String {
+      js-implicit context: Context, receiver: JSAny)(...arguments): String {
     // 1. Let O be ? RequireObjectCoercible(this value).
     // 2. Let S be ? ToString(O).
     const string: String = ToThisString(receiver, 'String.prototype.slice');

src/builtins/string-startswith.tq

@@ -10,13 +10,13 @@ namespace string {
 
   // https://tc39.github.io/ecma262/#sec-string.prototype.startswith
   transitioning javascript builtin StringPrototypeStartsWith(
-      js-implicit context: Context, receiver: Object)(...arguments): Boolean {
-    const searchString: Object = arguments[0];
-    const position: Object = arguments[1];
+      js-implicit context: Context, receiver: JSAny)(...arguments): Boolean {
+    const searchString: JSAny = arguments[0];
+    const position: JSAny = arguments[1];
     const kBuiltinName: constexpr string = 'String.prototype.startsWith';
 
     // 1. Let O be ? RequireObjectCoercible(this value).
-    const object: Object = RequireObjectCoercible(receiver, kBuiltinName);
+    const object: JSAny = RequireObjectCoercible(receiver, kBuiltinName);
 
     // 2. Let S be ? ToString(O).
     const string: String = ToString_Inline(context, object);

src/builtins/string-substring.tq

@@ -7,7 +7,7 @@ namespace string_substring {
   extern macro SubString(String, intptr, intptr): String;
 
   transitioning macro ToSmiBetweenZeroAnd(implicit context: Context)(
-      value: Object, limit: Smi): Smi {
+      value: JSAny, limit: Smi): Smi {
     const valueInt: Number =
         ToInteger_Inline(context, value, kTruncateMinusZero);
     typeswitch (valueInt) {
@@ -28,7 +28,7 @@ namespace string_substring {
 
   // ES6 #sec-string.prototype.substring
   transitioning javascript builtin StringPrototypeSubstring(
-      js-implicit context: Context, receiver: Object)(...arguments): String {
+      js-implicit context: Context, receiver: JSAny)(...arguments): String {
     // Check that {receiver} is coercible to Object and convert it to a String.
     const string: String = ToThisString(receiver, 'String.prototype.substring');
     const length = string.length_smi;

src/builtins/string.tq

@@ -7,14 +7,14 @@
 namespace string {
   // ES6 #sec-string.prototype.tostring
   transitioning javascript builtin
-  StringPrototypeToString(js-implicit context: Context)(receiver: Object):
+  StringPrototypeToString(js-implicit context: Context)(receiver: JSAny):
       Object {
     return ToThisValue(receiver, kString, 'String.prototype.toString');
   }
 
   // ES6 #sec-string.prototype.valueof
   transitioning javascript builtin
-  StringPrototypeValueOf(js-implicit context: Context)(receiver: Object):
+  StringPrototypeValueOf(js-implicit context: Context)(receiver: JSAny):
       Object {
     return ToThisValue(receiver, kString, 'String.prototype.valueOf');
   }
@@ -53,7 +53,7 @@ namespace string {
   }
 
   transitioning macro GenerateStringAt(implicit context: Context)(
-      receiver: Object, position: Object,
+      receiver: JSAny, position: JSAny,
       methodName: constexpr string): never labels
   IfInBounds(String, intptr, intptr), IfOutOfBounds {
     // Check that {receiver} is coercible to Object and convert it to a String.
@@ -71,8 +71,7 @@ namespace string {
 
   // ES6 #sec-string.prototype.charat
   transitioning javascript builtin StringPrototypeCharAt(
-      js-implicit context: Context,
-      receiver: Object)(position: Object): Object {
+      js-implicit context: Context, receiver: JSAny)(position: JSAny): Object {
     try {
       GenerateStringAt(receiver, position, 'String.prototype.charAt')
           otherwise IfInBounds, IfOutOfBounds;
@@ -88,8 +87,7 @@ namespace string {
 
   // ES6 #sec-string.prototype.charcodeat
   transitioning javascript builtin StringPrototypeCharCodeAt(
-      js-implicit context: Context,
-      receiver: Object)(position: Object): Object {
+      js-implicit context: Context, receiver: JSAny)(position: JSAny): Object {
     try {
       GenerateStringAt(receiver, position, 'String.prototype.charCodeAt')
           otherwise IfInBounds, IfOutOfBounds;
@@ -105,8 +103,7 @@ namespace string {
 
   // ES6 #sec-string.prototype.codepointat
   transitioning javascript builtin StringPrototypeCodePointAt(
-      js-implicit context: Context,
-      receiver: Object)(position: Object): Object {
+      js-implicit context: Context, receiver: JSAny)(position: JSAny): Object {
     try {
       GenerateStringAt(receiver, position, 'String.prototype.codePointAt')
           otherwise IfInBounds, IfOutOfBounds;
@@ -125,7 +122,7 @@ namespace string {
   // ES6 String.prototype.concat(...args)
   // ES6 #sec-string.prototype.concat
   transitioning javascript builtin StringPrototypeConcat(
-      js-implicit context: Context, receiver: Object)(...arguments): Object {
+      js-implicit context: Context, receiver: JSAny)(...arguments): Object {
     // Check that {receiver} is coercible to Object and convert it to a String.
     let string: String = ToThisString(receiver, 'String.prototype.concat');
 

src/builtins/typed-array-createtypedarray.tq

@@ -122,7 +122,7 @@ namespace typed_array_createtypedarray {
   // 22.2.4.2 TypedArray ( length )
   // ES #sec-typedarray-length
   transitioning macro ConstructByLength(implicit context: Context)(
-      map: Map, length: Object,
+      map: Map, length: JSAny,
       elementsInfo: typed_array::TypedArrayElementsInfo): JSTypedArray {
     const convertedLength: Number =
         ToInteger_Inline(context, length, kTruncateMinusZero);
@@ -141,7 +141,7 @@ namespace typed_array_createtypedarray {
   // 22.2.4.4 TypedArray ( object )
   // ES #sec-typedarray-object
   transitioning macro ConstructByArrayLike(implicit context: Context)(
-      map: Map, arrayLike: HeapObject, initialLength: Object,
+      map: Map, arrayLike: HeapObject, initialLength: JSAny,
       elementsInfo: typed_array::TypedArrayElementsInfo,
       bufferConstructor: JSReceiver): JSTypedArray {
     // The caller has looked up length on arrayLike, which is observable.
@@ -178,7 +178,7 @@ namespace typed_array_createtypedarray {
   // ES #sec-typedarray-object
   transitioning macro ConstructByIterable(implicit context: Context)(
       iterable: JSReceiver, iteratorFn: Callable): never
-      labels IfConstructByArrayLike(HeapObject, Object, JSReceiver) {
+      labels IfConstructByArrayLike(JSArray, Number, JSReceiver) {
     const array: JSArray =
         IterableToListMayPreserveHoles(context, iterable, iteratorFn);
     goto IfConstructByArrayLike(array, array.length, GetArrayBufferFunction());
@@ -188,7 +188,7 @@ namespace typed_array_createtypedarray {
   // ES #sec-typedarray-typedarray
   transitioning macro ConstructByTypedArray(implicit context: Context)(
       srcTypedArray: JSTypedArray): never
-      labels IfConstructByArrayLike(HeapObject, Object, JSReceiver) {
+      labels IfConstructByArrayLike(JSTypedArray, Number, JSReceiver) {
     let bufferConstructor: JSReceiver = GetArrayBufferFunction();
     const srcBuffer: JSArrayBuffer = srcTypedArray.buffer;
     // TODO(petermarshall): Throw on detached typedArray.
@@ -210,7 +210,7 @@ namespace typed_array_createtypedarray {
   // 22.2.4.5 TypedArray ( buffer, byteOffset, length )
   // ES #sec-typedarray-buffer-byteoffset-length
   transitioning macro ConstructByArrayBuffer(implicit context: Context)(
-      map: Map, buffer: JSArrayBuffer, byteOffset: Object, length: Object,
+      map: Map, buffer: JSArrayBuffer, byteOffset: JSAny, length: JSAny,
       elementsInfo: typed_array::TypedArrayElementsInfo): JSTypedArray {
     try {
       let offset: uintptr = 0;
@@ -294,7 +294,7 @@ namespace typed_array_createtypedarray {
 
   transitioning macro ConstructByJSReceiver(implicit context:
                                                 Context)(obj: JSReceiver): never
-      labels IfConstructByArrayLike(HeapObject, Object, JSReceiver) {
+      labels IfConstructByArrayLike(JSReceiver, Number, JSReceiver) {
     try {
       const iteratorMethod: Object =
           GetIteratorMethod(obj) otherwise IfIteratorUndefined;
@@ -304,7 +304,7 @@ namespace typed_array_createtypedarray {
           otherwise IfConstructByArrayLike;
     }
     label IfIteratorUndefined {
-      const lengthObj: Object = GetProperty(obj, kLengthString);
+      const lengthObj: JSAny = GetProperty(obj, kLengthString);
       const length: Smi = ToSmiLength(lengthObj)
           otherwise goto IfInvalidLength(lengthObj);
       goto IfConstructByArrayLike(obj, length, GetArrayBufferFunction());
@@ -317,8 +317,8 @@ namespace typed_array_createtypedarray {
   // 22.2.4 The TypedArray Constructors
   // ES #sec-typedarray-constructors
   transitioning builtin CreateTypedArray(
-      context: Context, target: JSFunction, newTarget: JSReceiver, arg1: Object,
-      arg2: Object, arg3: Object): JSTypedArray {
+      context: Context, target: JSFunction, newTarget: JSReceiver, arg1: JSAny,
+      arg2: JSAny, arg3: JSAny): JSTypedArray {
     assert(IsConstructor(target));
     // 4. Let O be ? AllocateTypedArray(constructorName, NewTarget,
     // "%TypedArrayPrototype%").
@@ -345,16 +345,16 @@ namespace typed_array_createtypedarray {
         }
         // The first argument was a number or fell through and is treated as
         // a number. https://tc39.github.io/ecma262/#sec-typedarray-length
-        case (lengthObj: HeapObject): {
+        case (lengthObj: JSAny): {
           goto IfConstructByLength(lengthObj);
         }
       }
     }
-    label IfConstructByLength(length: Object) {
+    label IfConstructByLength(length: JSAny) {
       return ConstructByLength(map, length, elementsInfo);
     }
     label IfConstructByArrayLike(
-        arrayLike: HeapObject, length: Object, bufferConstructor: JSReceiver) {
+        arrayLike: JSReceiver, length: Number, bufferConstructor: JSReceiver) {
       return ConstructByArrayLike(
           map, arrayLike, length, elementsInfo, bufferConstructor);
     }
@@ -362,8 +362,8 @@ namespace typed_array_createtypedarray {
 
   transitioning macro TypedArraySpeciesCreate(implicit context: Context)(
       methodName: constexpr string, numArgs: constexpr int31,
-      exemplar: JSTypedArray, arg0: Object, arg1: Object,
-      arg2: Object): JSTypedArray {
+      exemplar: JSTypedArray, arg0: JSAny, arg1: JSAny,
+      arg2: JSAny): JSTypedArray {
     const defaultConstructor = GetDefaultConstructor(exemplar);
 
     try {
@@ -386,7 +386,7 @@ namespace typed_array_createtypedarray {
 
       // TODO(pwong): Simplify and remove numArgs when varargs are supported in
       // macros.
-      let newObj: Object = Undefined;
+      let newObj: JSAny = Undefined;
       if constexpr (numArgs == 1) {
         newObj = Construct(constructor, arg0);
       } else {

src/builtins/typed-array-every.tq

@@ -9,7 +9,7 @@ namespace typed_array_every {
 
   transitioning macro EveryAllElements(implicit context: Context)(
       array: typed_array::AttachedJSTypedArray, callbackfn: Callable,
-      thisArg: Object): Boolean {
+      thisArg: JSAny): Boolean {
     let witness = typed_array::NewAttachedJSTypedArrayWitness(array);
     // TODO(v8:4153): Support huge TypedArrays here.
     const length =
@@ -17,7 +17,7 @@ namespace typed_array_every {
     for (let k: Smi = 0; k < length; k++) {
       // BUG(4895): We should throw on detached buffers rather than simply exit.
       witness.Recheck() otherwise break;
-      const value: Object = witness.Load(k);
+      const value: JSAny = witness.Load(k);
       const result =
           Call(context, callbackfn, thisArg, value, k, witness.GetStable());
       if (!ToBoolean(result)) {
@@ -29,7 +29,7 @@ namespace typed_array_every {
 
   // https://tc39.github.io/ecma262/#sec-%typedarray%.prototype.every
   transitioning javascript builtin
-  TypedArrayPrototypeEvery(js-implicit context: Context, receiver: Object)(
+  TypedArrayPrototypeEvery(js-implicit context: Context, receiver: JSAny)(
       ...arguments): Object {
     // arguments[0] = callback
     // arguments[1] = thisArg

src/builtins/typed-array-filter.tq

@@ -10,7 +10,7 @@ namespace typed_array_filter {
 
   // https://tc39.github.io/ecma262/#sec-%typedarray%.prototype.filter
   transitioning javascript builtin TypedArrayPrototypeFilter(
-      js-implicit context: Context, receiver: Object)(...arguments): Object {
+      js-implicit context: Context, receiver: JSAny)(...arguments): Object {
     // arguments[0] = callback
     // arguments[1] = thisArg
     try {
@@ -29,7 +29,7 @@ namespace typed_array_filter {
           otherwise ThrowTypeError(kCalledNonCallable, arguments[0]);
 
       // 5. If thisArg is present, let T be thisArg; else let T be undefined.
-      const thisArg: Object = arguments[1];
+      const thisArg: JSAny = arguments[1];
 
       // 6. Let kept be a new empty List.
       let kept = growable_fixed_array::NewGrowableFixedArray();
@@ -43,11 +43,11 @@ namespace typed_array_filter {
 
         // a. Let Pk be ! ToString(k).
         // b. Let kValue be ? Get(O, Pk).
-        const value: Object = witness.Load(k);
+        const value: JSAny = witness.Load(k);
 
         // c. Let selected be ToBoolean(? Call(callbackfn, T, « kValue, k, O
         // »)).
-        const selected: Object =
+        const selected: JSAny =
             Call(context, callbackfn, thisArg, value, k, witness.GetStable());
 
         // d. If selected is true, then

src/builtins/typed-array-find.tq

@@ -9,7 +9,7 @@ namespace typed_array_find {
 
   transitioning macro FindAllElements(implicit context: Context)(
       array: typed_array::AttachedJSTypedArray, callbackfn: Callable,
-      thisArg: Object): Object {
+      thisArg: JSAny): Object {
     let witness = typed_array::NewAttachedJSTypedArrayWitness(array);
     // TODO(v8:4153): Support huge TypedArrays here.
     const length =
@@ -17,7 +17,7 @@ namespace typed_array_find {
     for (let k: Smi = 0; k < length; k++) {
       // BUG(4895): We should throw on detached buffers rather than simply exit.
       witness.Recheck() otherwise break;
-      const value: Object = witness.Load(k);
+      const value: JSAny = witness.Load(k);
       const result =
           Call(context, callbackfn, thisArg, value, k, witness.GetStable());
       if (ToBoolean(result)) {
@@ -29,7 +29,7 @@ namespace typed_array_find {
 
   // https://tc39.github.io/ecma262/#sec-%typedarray%.prototype.find
   transitioning javascript builtin
-  TypedArrayPrototypeFind(js-implicit context: Context, receiver: Object)(
+  TypedArrayPrototypeFind(js-implicit context: Context, receiver: JSAny)(
       ...arguments): Object {
     // arguments[0] = callback
     // arguments[1] = thisArg

src/builtins/typed-array-findindex.tq

@@ -9,7 +9,7 @@ namespace typed_array_findindex {
 
   transitioning macro FindIndexAllElements(implicit context: Context)(
       array: typed_array::AttachedJSTypedArray, callbackfn: Callable,
-      thisArg: Object): Number {
+      thisArg: JSAny): Number {
     let witness = typed_array::NewAttachedJSTypedArrayWitness(array);
     // TODO(v8:4153): Support huge TypedArrays here.
     const length =
@@ -17,7 +17,7 @@ namespace typed_array_findindex {
     for (let k: Smi = 0; k < length; k++) {
       // BUG(4895): We should throw on detached buffers rather than simply exit.
       witness.Recheck() otherwise break;
-      const value: Object = witness.Load(k);
+      const value: JSAny = witness.Load(k);
       const result =
           Call(context, callbackfn, thisArg, value, k, witness.GetStable());
       if (ToBoolean(result)) {
@@ -29,7 +29,7 @@ namespace typed_array_findindex {
 
   // https://tc39.github.io/ecma262/#sec-%typedarray%.prototype.findIndex
   transitioning javascript builtin
-  TypedArrayPrototypeFindIndex(js-implicit context: Context, receiver: Object)(
+  TypedArrayPrototypeFindIndex(js-implicit context: Context, receiver: JSAny)(
       ...arguments): Object {
     // arguments[0] = callback
     // arguments[1] = thisArg.

src/builtins/typed-array-foreach.tq

@@ -9,7 +9,7 @@ namespace typed_array_foreach {
 
   transitioning macro ForEachAllElements(implicit context: Context)(
       array: typed_array::AttachedJSTypedArray, callbackfn: Callable,
-      thisArg: Object): Object {
+      thisArg: JSAny): Undefined {
     let witness = typed_array::NewAttachedJSTypedArrayWitness(array);
     // TODO(v8:4153): Support huge TypedArrays here.
     const length =
@@ -17,7 +17,7 @@ namespace typed_array_foreach {
     for (let k: Smi = 0; k < length; k++) {
       // BUG(4895): We should throw on detached buffers rather than simply exit.
       witness.Recheck() otherwise break;
-      const value: Object = witness.Load(k);
+      const value: JSAny = witness.Load(k);
       Call(context, callbackfn, thisArg, value, k, witness.GetStable());
     }
     return Undefined;
@@ -25,8 +25,8 @@ namespace typed_array_foreach {
 
   // https://tc39.github.io/ecma262/#sec-%typedarray%.prototype.every
   transitioning javascript builtin
-  TypedArrayPrototypeForEach(js-implicit context: Context, receiver: Object)(
-      ...arguments): Object {
+  TypedArrayPrototypeForEach(js-implicit context: Context, receiver: JSAny)(
+      ...arguments): Undefined {
     // arguments[0] = callback
     // arguments[1] = this_arg.
 

src/builtins/typed-array-reduce.tq

@@ -9,7 +9,7 @@ namespace typed_array_reduce {
 
   transitioning macro ReduceAllElements(implicit context: Context)(
       array: typed_array::AttachedJSTypedArray, callbackfn: Callable,
-      initialValue: Object): Object {
+      initialValue: JSAny | TheHole): JSAny {
     let witness = typed_array::NewAttachedJSTypedArrayWitness(array);
     // TODO(v8:4153): Support huge TypedArrays here.
     const length =
@@ -18,24 +18,31 @@ namespace typed_array_reduce {
     for (let k: Smi = 0; k < length; k++) {
       // BUG(4895): We should throw on detached buffers rather than simply exit.
       witness.Recheck() otherwise break;
-      const value: Object = witness.Load(k);
-      if (accumulator == TheHole) {
-        accumulator = value;
-      } else {
-        accumulator = Call(
-            context, callbackfn, Undefined, accumulator, value, k,
-            witness.GetStable());
+      const value: JSAny = witness.Load(k);
+      typeswitch (accumulator) {
+        case (TheHole): {
+          accumulator = value;
+        }
+        case (accumulatorNotHole: JSAny): {
+          accumulator = Call(
+              context, callbackfn, Undefined, accumulatorNotHole, value, k,
+              witness.GetStable());
+        }
       }
     }
-    if (accumulator == TheHole) {
-      ThrowTypeError(kReduceNoInitial, kBuiltinName);
+    typeswitch (accumulator) {
+      case (TheHole): {
+        ThrowTypeError(kReduceNoInitial, kBuiltinName);
+      }
+      case (accumulator: JSAny): {
+        return accumulator;
+      }
     }
-    return accumulator;
   }
 
   // https://tc39.github.io/ecma262/#sec-%typedarray%.prototype.reduce
   transitioning javascript builtin
-  TypedArrayPrototypeReduce(js-implicit context: Context, receiver: Object)(
+  TypedArrayPrototypeReduce(js-implicit context: Context, receiver: JSAny)(
       ...arguments): Object {
     // arguments[0] = callback
     // arguments[1] = initialValue.

src/builtins/typed-array-reduceright.tq

@@ -9,7 +9,7 @@ namespace typed_array_reduceright {
 
   transitioning macro ReduceRightAllElements(implicit context: Context)(
       array: typed_array::AttachedJSTypedArray, callbackfn: Callable,
-      initialValue: Object): Object {
+      initialValue: JSAny | TheHole): JSAny {
     let witness = typed_array::NewAttachedJSTypedArrayWitness(array);
     // TODO(v8:4153): Support huge TypedArrays here.
     const length =
@@ -18,25 +18,32 @@ namespace typed_array_reduceright {
     for (let k: Smi = length - 1; k >= 0; k--) {
       // BUG(4895): We should throw on detached buffers rather than simply exit.
       witness.Recheck() otherwise break;
-      const value: Object = witness.Load(k);
-      if (accumulator == TheHole) {
-        accumulator = value;
-      } else {
-        accumulator = Call(
-            context, callbackfn, Undefined, accumulator, value, k,
-            witness.GetStable());
+      const value: JSAny = witness.Load(k);
+      typeswitch (accumulator) {
+        case (TheHole): {
+          accumulator = value;
+        }
+        case (accumulatorNotHole: JSAny): {
+          accumulator = Call(
+              context, callbackfn, Undefined, accumulatorNotHole, value, k,
+              witness.GetStable());
+        }
       }
     }
-    if (accumulator == TheHole) {
-      ThrowTypeError(kReduceNoInitial, kBuiltinName);
+    typeswitch (accumulator) {
+      case (TheHole): {
+        ThrowTypeError(kReduceNoInitial, kBuiltinName);
+      }
+      case (accumulator: JSAny): {
+        return accumulator;
+      }
     }
-    return accumulator;
   }
 
   // https://tc39.github.io/ecma262/#sec-%typedarray%.prototype.reduceright
   transitioning javascript builtin
-  TypedArrayPrototypeReduceRight(
-      js-implicit context: Context, receiver: Object)(...arguments): Object {
+  TypedArrayPrototypeReduceRight(js-implicit context: Context, receiver: JSAny)(
+      ...arguments): Object {
     // arguments[0] = callback
     // arguments[1] = initialValue.
     try {

src/builtins/typed-array-slice.tq

@@ -53,7 +53,7 @@ namespace typed_array_slice {
 
   // https://tc39.github.io/ecma262/#sec-%typedarray%.prototype.slice
   transitioning javascript builtin TypedArrayPrototypeSlice(
-      js-implicit context: Context, receiver: Object)(...arguments): Object {
+      js-implicit context: Context, receiver: JSAny)(...arguments): Object {
     // arguments[0] = start
     // arguments[1] = end
 

src/builtins/typed-array-some.tq

@@ -9,7 +9,7 @@ namespace typed_array_some {
 
   transitioning macro SomeAllElements(implicit context: Context)(
       array: typed_array::AttachedJSTypedArray, callbackfn: Callable,
-      thisArg: Object): Boolean {
+      thisArg: JSAny): Boolean {
     let witness = typed_array::NewAttachedJSTypedArrayWitness(array);
     // TODO(v8:4153): Support huge TypedArrays here.
     const length =
@@ -17,7 +17,7 @@ namespace typed_array_some {
     for (let k: Smi = 0; k < length; k++) {
       // BUG(4895): We should throw on detached buffers rather than simply exit.
       witness.Recheck() otherwise break;
-      const value: Object = witness.Load(k);
+      const value: JSAny = witness.Load(k);
       const result =
           Call(context, callbackfn, thisArg, value, k, witness.GetStable());
       if (ToBoolean(result)) {
@@ -29,7 +29,7 @@ namespace typed_array_some {
 
   // https://tc39.github.io/ecma262/#sec-%typedarray%.prototype.some
   transitioning javascript builtin
-  TypedArrayPrototypeSome(js-implicit context: Context, receiver: Object)(
+  TypedArrayPrototypeSome(js-implicit context: Context, receiver: JSAny)(
       ...arguments): Object {
     // arguments[0] = callback
     // arguments[1] = thisArg.

src/builtins/typed-array-subarray.tq

@@ -6,7 +6,7 @@ namespace typed_array_subarray {
   // ES %TypedArray%.prototype.subarray
   transitioning javascript builtin TypedArrayPrototypeSubArray(
       js-implicit context: Context,
-      receiver: Object)(...arguments): JSTypedArray {
+      receiver: JSAny)(...arguments): JSTypedArray {
     const methodName: constexpr string = '%TypedArray%.prototype.subarray';
 
     // 1. Let O be the this value.

src/builtins/typed-array.tq

@@ -51,9 +51,9 @@ namespace typed_array {
     sizeLog2: uintptr;
     kind: ElementsKind;
   }
-  extern runtime TypedArraySortFast(Context, Object): JSTypedArray;
+  extern runtime TypedArraySortFast(Context, JSAny): JSTypedArray;
   extern macro TypedArrayBuiltinsAssembler::ValidateTypedArray(
-      Context, Object, constexpr string): JSTypedArray;
+      Context, JSAny, constexpr string): JSTypedArray;
 
   extern macro TypedArrayBuiltinsAssembler::CallCMemcpy(
       RawPtr, RawPtr, uintptr): void;
@@ -72,10 +72,10 @@ namespace typed_array {
   extern macro LoadFixedTypedArrayElementAsTagged(
       RawPtr, Smi, constexpr ElementsKind): Numeric;
   extern macro StoreJSTypedArrayElementFromTagged(
-      Context, JSTypedArray, Smi, Object, constexpr ElementsKind);
+      Context, JSTypedArray, Smi, JSAny, constexpr ElementsKind);
 
-  type LoadFn = builtin(Context, JSTypedArray, Smi) => Object;
-  type StoreFn = builtin(Context, JSTypedArray, Smi, Object) => Object;
+  type LoadFn = builtin(Context, JSTypedArray, Smi) => JSAny;
+  type StoreFn = builtin(Context, JSTypedArray, Smi, JSAny) => JSAny;
 
   // AttachedJSTypedArray guards that the array's buffer is not detached.
   transient type AttachedJSTypedArray extends JSTypedArray;
@@ -100,7 +100,7 @@ namespace typed_array {
       this.unstable = %RawDownCast<AttachedJSTypedArray>(this.stable);
     }
 
-    Load(implicit context: Context)(k: Smi): Object {
+    Load(implicit context: Context)(k: Smi): JSAny {
       const lf: LoadFn = this.loadfn;
       return lf(context, this.unstable, k);
     }
@@ -190,14 +190,14 @@ namespace typed_array {
   }
 
   builtin LoadFixedElement<T: type>(
-      _context: Context, array: JSTypedArray, index: Smi): Object {
+      _context: Context, array: JSTypedArray, index: Smi): JSAny {
     return LoadFixedTypedArrayElementAsTagged(
         array.data_ptr, index, KindForArrayType<T>());
   }
 
   builtin StoreFixedElement<T: type>(
       context: Context, typedArray: JSTypedArray, index: Smi,
-      value: Object): Object {
+      value: JSAny): JSAny {
     StoreJSTypedArrayElementFromTagged(
         context, typedArray, index, value, KindForArrayType<T>());
     return Undefined;
@@ -205,7 +205,7 @@ namespace typed_array {
 
   transitioning macro CallCompare(
       implicit context: Context, array: JSTypedArray,
-      comparefn: Callable)(a: Object, b: Object): Number {
+      comparefn: Callable)(a: JSAny, b: JSAny): Number {
     // a. Let v be ? ToNumber(? Call(comparefn, undefined, x, y)).
     const v: Number =
         ToNumber_Inline(context, Call(context, comparefn, Undefined, a, b));
@@ -238,8 +238,8 @@ namespace typed_array {
         target.objects[targetIndex] = source.objects[left++];
       } else if (left < middle) {
         // If both have elements, we need to compare.
-        const leftElement: Object = source.objects[left];
-        const rightElement: Object = source.objects[right];
+        const leftElement = UnsafeCast<JSAny>(source.objects[left]);
+        const rightElement = UnsafeCast<JSAny>(source.objects[right]);
         if (CallCompare(leftElement, rightElement) <= 0) {
           target.objects[targetIndex] = leftElement;
           left++;
@@ -259,7 +259,7 @@ namespace typed_array {
   transitioning builtin
   TypedArrayMergeSort(
       implicit context: Context, array: JSTypedArray, comparefn: Callable)(
-      source: FixedArray, from: Smi, to: Smi, target: FixedArray): Object {
+      source: FixedArray, from: Smi, to: Smi, target: FixedArray): JSAny {
     assert(to - from > 1);
     const middle: Smi = from + ((to - from) >> 1);
 
@@ -277,17 +277,16 @@ namespace typed_array {
   // https://tc39.github.io/ecma262/#sec-%typedarray%.prototype.sort
   transitioning javascript builtin TypedArrayPrototypeSort(
       js-implicit context: Context,
-      receiver: Object)(...arguments): JSTypedArray {
+      receiver: JSAny)(...arguments): JSTypedArray {
     // 1. If comparefn is not undefined and IsCallable(comparefn) is false,
     //    throw a TypeError exception.
-    const comparefnObj: Object =
-        arguments.length > 0 ? arguments[0] : Undefined;
+    const comparefnObj: JSAny = arguments.length > 0 ? arguments[0] : Undefined;
     if (comparefnObj != Undefined && !TaggedIsCallable(comparefnObj)) {
       ThrowTypeError(kBadSortComparisonFunction, comparefnObj);
     }
 
     // 2. Let obj be the this value.
-    const obj: Object = receiver;
+    const obj: JSAny = receiver;
 
     // 3. Let buffer be ? ValidateTypedArray(obj).
     //    ValidateTypedArray currently returns the array, not the ViewBuffer.
@@ -363,7 +362,7 @@ namespace typed_array {
     const work2: FixedArray = AllocateZeroedFixedArray(Convert<intptr>(len));
 
     for (let i: Smi = 0; i < len; ++i) {
-      const element: Object = loadfn(context, array, i);
+      const element: JSAny = loadfn(context, array, i);
       work1.objects[i] = element;
       work2.objects[i] = element;
     }
@@ -372,7 +371,7 @@ namespace typed_array {
 
     // work1 contains the sorted numbers. Write them back.
     for (let i: Smi = 0; i < len; ++i)
-      storefn(context, array, i, work1.objects[i]);
+      storefn(context, array, i, UnsafeCast<JSAny>(work1.objects[i]));
 
     return array;
   }

src/objects/objects-inl.h

@@ -133,6 +133,13 @@ bool Object::IsNullOrUndefined() const {
 
 bool Object::IsZero() const { return *this == Smi::zero(); }
 
+bool Object::IsPublicSymbol() const {
+  return IsSymbol() && !Symbol::cast(*this).is_private();
+}
+bool Object::IsPrivateSymbol() const {
+  return IsSymbol() && Symbol::cast(*this).is_private();
+}
+
 bool Object::IsNoSharedNameSentinel() const {
   return *this == SharedFunctionInfo::kNoSharedNameSentinel;
 }

src/objects/objects.h

@@ -289,6 +289,8 @@ class Object : public TaggedImpl<HeapObjectReferenceType::STRONG, Address> {
 
   V8_INLINE bool IsZero() const;
   V8_INLINE bool IsNoSharedNameSentinel() const;
+  V8_INLINE bool IsPrivateSymbol() const;
+  V8_INLINE bool IsPublicSymbol() const;
 
   enum class Conversion { kToNumber, kToNumeric };
 

src/torque/constants.h

@@ -28,6 +28,7 @@ static const char* const JS_FUNCTION_TYPE_STRING = "JSFunction";
 static const char* const MAP_TYPE_STRING = "Map";
 static const char* const OBJECT_TYPE_STRING = "Object";
 static const char* const HEAP_OBJECT_TYPE_STRING = "HeapObject";
+static const char* const JSANY_TYPE_STRING = "JSAny";
 static const char* const JSOBJECT_TYPE_STRING = "JSObject";
 static const char* const SMI_TYPE_STRING = "Smi";
 static const char* const TAGGED_TYPE_STRING = "Tagged";

src/torque/implementation-visitor.cc

@@ -468,13 +468,13 @@ void ImplementationVisitor::Visit(Builtin* builtin) {
                     : "UncheckedCast<Object>(Parameter(Descriptor::kReceiver))")
             << ";\n";
         source_out() << "USE(" << generated_name << ");\n";
-        expected_type = TypeOracle::GetObjectType();
+        expected_type = TypeOracle::GetJSAnyType();
       } else if (param_name == "newTarget") {
         source_out() << "  TNode<Object> " << generated_name
                      << " = UncheckedCast<Object>(Parameter("
                      << "Descriptor::kJSNewTarget));\n";
         source_out() << "USE(" << generated_name << ");\n";
-        expected_type = TypeOracle::GetObjectType();
+        expected_type = TypeOracle::GetJSAnyType();
       } else if (param_name == "target") {
         source_out() << "  TNode<JSFunction> " << generated_name
                      << " = UncheckedCast<JSFunction>(Parameter("
@@ -2264,9 +2264,10 @@ VisitResult ImplementationVisitor::GenerateCall(
         size_t j = 0;
         for (auto t : callable->signature().labels[i].types) {
           const Type* parameter_type = label->parameter_types[j];
-          if (parameter_type != t) {
-            ReportError("mismatch of label parameters (expected ", *t, " got ",
-                        parameter_type, " for parameter ", i + 1, ")");
+          if (!t->IsSubtypeOf(parameter_type)) {
+            ReportError("mismatch of label parameters (label expects ",
+                        *parameter_type, " but macro produces ", *t,
+                        " for parameter ", i + 1, ")");
           }
           j++;
         }

src/torque/instructions.cc

@@ -133,7 +133,7 @@ void CallCsaMacroInstruction::TypeInstruction(Stack<const Type*>* stack,
 
   if (catch_block) {
     Stack<const Type*> catch_stack = *stack;
-    catch_stack.Push(TypeOracle::GetObjectType());
+    catch_stack.Push(TypeOracle::GetJSAnyType());
     (*catch_block)->SetInputTypes(catch_stack);
   }
 
@@ -170,7 +170,7 @@ void CallCsaMacroAndBranchInstruction::TypeInstruction(
 
   if (catch_block) {
     Stack<const Type*> catch_stack = *stack;
-    catch_stack.Push(TypeOracle::GetObjectType());
+    catch_stack.Push(TypeOracle::GetJSAnyType());
     (*catch_block)->SetInputTypes(catch_stack);
   }
 
@@ -201,7 +201,7 @@ void CallBuiltinInstruction::TypeInstruction(Stack<const Type*>* stack,
 
   if (catch_block) {
     Stack<const Type*> catch_stack = *stack;
-    catch_stack.Push(TypeOracle::GetObjectType());
+    catch_stack.Push(TypeOracle::GetJSAnyType());
     (*catch_block)->SetInputTypes(catch_stack);
   }
 
@@ -236,7 +236,7 @@ void CallRuntimeInstruction::TypeInstruction(Stack<const Type*>* stack,
 
   if (catch_block) {
     Stack<const Type*> catch_stack = *stack;
-    catch_stack.Push(TypeOracle::GetObjectType());
+    catch_stack.Push(TypeOracle::GetJSAnyType());
     (*catch_block)->SetInputTypes(catch_stack);
   }
 

src/torque/torque-parser.cc

@@ -1136,7 +1136,7 @@ base::Optional<ParseResult> MakeCatchBlock(ParseResultIterator* child_results) {
   ParameterList parameters;
   parameters.names.push_back(MakeNode<Identifier>(variable));
   parameters.types.push_back(MakeNode<BasicTypeExpression>(
-      std::vector<std::string>{}, "Object", std::vector<TypeExpression*>{}));
+      std::vector<std::string>{}, "JSAny", std::vector<TypeExpression*>{}));
   parameters.has_varargs = false;
   LabelBlock* result = MakeNode<LabelBlock>(
       MakeNode<Identifier>(kCatchLabelName), std::move(parameters), body);

src/torque/type-oracle.h

@@ -143,6 +143,10 @@ class TypeOracle : public ContextualClass<TypeOracle> {
     return Get().GetBuiltinType(HEAP_OBJECT_TYPE_STRING);
   }
 
+  static const Type* GetJSAnyType() {
+    return Get().GetBuiltinType(JSANY_TYPE_STRING);
+  }
+
   static const Type* GetJSObjectType() {
     return Get().GetBuiltinType(JSOBJECT_TYPE_STRING);
   }

test/torque/test-torque.tq

@@ -83,11 +83,11 @@ namespace test {
     }
   }
 
-  builtin GenericBuiltinTest<T: type>(_c: Context, _param: T): Object {
+  builtin GenericBuiltinTest<T: type>(_c: Context, _param: T): JSAny {
     return Null;
   }
 
-  GenericBuiltinTest<Object>(_c: Context, param: Object): Object {
+  GenericBuiltinTest<JSAny>(_c: Context, param: JSAny): JSAny {
     return param;
   }
 
@@ -95,8 +95,8 @@ namespace test {
   macro TestBuiltinSpecialization(c: Context) {
     check(GenericBuiltinTest<Smi>(c, 0) == Null);
     check(GenericBuiltinTest<Smi>(c, 1) == Null);
-    check(GenericBuiltinTest<Object>(c, Undefined) == Undefined);
-    check(GenericBuiltinTest<Object>(c, Undefined) == Undefined);
+    check(GenericBuiltinTest<JSAny>(c, Undefined) == Undefined);
+    check(GenericBuiltinTest<JSAny>(c, Undefined) == Undefined);
   }
 
   macro LabelTestHelper4(flag: constexpr bool): never
@@ -202,9 +202,8 @@ namespace test {
 
   @export
   macro TestFunctionPointerToGeneric(c: Context) {
-    const fptr1: builtin(Context, Smi) => Object = GenericBuiltinTest<Smi>;
-    const fptr2: builtin(Context, Object) => Object =
-        GenericBuiltinTest<Object>;
+    const fptr1: builtin(Context, Smi) => JSAny = GenericBuiltinTest<Smi>;
+    const fptr2: builtin(Context, JSAny) => JSAny = GenericBuiltinTest<JSAny>;
 
     check(fptr1(c, 0) == Null);
     check(fptr1(c, 1) == Null);
@@ -212,7 +211,7 @@ namespace test {
     check(fptr2(c, Undefined) == Undefined);
   }
 
-  type ObjectToObject = builtin(Context, Object) => Object;
+  type ObjectToObject = builtin(Context, JSAny) => JSAny;
   @export
   macro TestTypeAlias(x: ObjectToObject): BuiltinPtr {
     return x;
@@ -452,7 +451,7 @@ namespace test {
 
   @export
   macro TestSubtyping(x: Smi) {
-    const _foo: Object = x;
+    const _foo: JSAny = x;
   }
 
   macro IncrementIfSmi<A: type>(x: A): A {
@@ -627,7 +626,7 @@ namespace test {
   @export
   macro TestQualifiedAccess(implicit context: Context)() {
     const s: Smi = 0;
-    check(!array::IsJSArray(s));
+    check(!Is<JSArray>(s));
   }
 
   @export
@@ -685,14 +684,14 @@ namespace test {
   @export
   macro TestIterator(implicit context: Context)(o: JSReceiver, map: Map) {
     try {
-      const t1: Object = iterator::GetIteratorMethod(o);
+      const t1: JSAny = iterator::GetIteratorMethod(o);
       const t2: iterator::IteratorRecord = iterator::GetIterator(o);
 
-      const _t3: Object = iterator::IteratorStep(t2) otherwise Fail;
-      const _t4: Object = iterator::IteratorStep(t2, map) otherwise Fail;
+      const _t3: JSAny = iterator::IteratorStep(t2) otherwise Fail;
+      const _t4: JSAny = iterator::IteratorStep(t2, map) otherwise Fail;
 
-      const t5: Object = iterator::IteratorValue(o);
-      const _t6: Object = iterator::IteratorValue(o, map);
+      const t5: JSAny = iterator::IteratorValue(o);
+      const _t6: JSAny = iterator::IteratorValue(o, map);
 
       const _t7: JSArray = iterator::IterableToList(t1, t1);
 

tools/torque/format-torque.py

@@ -20,18 +20,9 @@ kPercentEscape = r'α';  # Unicode alpha
 def preprocess(input):
   input = re.sub(r'(if\s+)constexpr(\s*\()', r'\1/*COxp*/\2', input)
   input = re.sub(r'(\s+)operator\s*(\'[^\']+\')', r'\1/*_OPE \2*/', input)
-
-  # Mangle typeswitches to look like switch statements with the extra type
-  # information and syntax encoded in comments.
-  input = re.sub(r'(\s+)typeswitch\s*\(', r'\1/*_TYPE*/switch (', input)
-  input = re.sub(r'(\s+)case\s*\(\s*([^\:]+)\s*\)(\s*)\:\s*deferred',
-      r'\1case \2: /*_TSXDEFERRED_*/', input)
-  input = re.sub(r'(\s+)case\s*\(\s*([^\:]+)\s*\)(\s*)\:',
-      r'\1case \2: /*_TSX*/', input)
-  input = re.sub(r'(\s+)case\s*\(\s*([^\s]+)\s*\:\s*([^\:]+)\s*\)(\s*)\:\s*deferred',
-      r'\1case \3: /*_TSVDEFERRED_\2:*/', input)
-  input = re.sub(r'(\s+)case\s*\(\s*([^\s]+)\s*\:\s*([^\:]+)\s*\)(\s*)\:',
-      r'\1case \3: /*_TSV\2:*/', input)
+  input = re.sub(r'\btypeswitch\s*(\([^{]*\))\s{', r' if /*tPsW*/ \1 {', input)
+  input = re.sub(r'\bcase\s*(\([^{]*\))\s*:\s*deferred\s*{', r' if /*cAsEdEfF*/ \1 {', input)
+  input = re.sub(r'\bcase\s*(\([^{]*\))\s*:\s*{', r' if /*cA*/ \1 {', input)
 
   # Add extra space around | operators to fix union types later.
   while True:
@@ -65,15 +56,9 @@ def postprocess(output):
   output = re.sub(r'(\S+)\s*: type([,>])', r'\1: type\2', output)
   output = re.sub(r'(\n\s*)labels( [A-Z])', r'\1    labels\2', output)
   output = re.sub(r'\/\*_OPE \'([^\']+)\'\*\/', r"operator '\1'", output)
-  output = re.sub(r'\/\*_TYPE\*\/(\s*)switch', r'typeswitch', output)
-  output = re.sub(r'case (\w+)\:\s*\/\*_TSXDEFERRED_\*\/',
-      r'case (\1): deferred', output)
-  output = re.sub(r'case (\w+)\:\s*\/\*_TSX\*\/',
-      r'case (\1):', output)
-  output = re.sub(r'case (\w+)\:\s*\/\*_TSVDEFERRED_([^\:]+)\:\*\/',
-      r'case (\2: \1): deferred', output)
-  output = re.sub(r'case (\w+)\:\s*\/\*_TSV([^\:]+)\:\*\/',
-      r'case (\2: \1):', output)
+  output = re.sub(r'\bif\s*\/\*tPsW\*\/', r'typeswitch', output)
+  output = re.sub(r'\bif\s*\/\*cA\*\/\s*(\([^{]*\))\s*{', r'case \1: {', output)
+  output = re.sub(r'\bif\s*\/\*cAsEdEfF\*\/\s*(\([^{]*\))\s*{', r'case \1: deferred {', output)
   output = re.sub(r'\n_GeNeRaTeS00_\s*\/\*([^@]+)@\*\/',
       r"\n    generates '\1'", output)
   output = re.sub(r'_GeNeRaTeS00_\s*\/\*([^@]+)@\*\/',