Prepack Serializer Bugs Revealed by test262

01.md

The Map value is serialized, but not visited.

I’ve seen other invariant violations of this nature. For instance class O extends Object {}.

Input

class M extends Map {}

var map = new M([{ foo: "bar" }]);

map.set("bar", "baz");

Error

=== serialized but not visited values
=== visited but not serialized values
[object], hash: 1, intrinsic name: Map
  referenced by 1 scopes
      =>main(#0)

Invariant Violation: serialized 6 of 7
debug-fb-www.js:207
This is likely a bug in Prepack, not your code. Feel free to open an issue on GitHub.

02.md

Input

class C {
  get p() {}
}

Output

(function () {
  var _$0 = this;

  var _0 = class {
    get p() {}

  };

  _0.prototype.p = void 0; // <-------------- `p` is already declared to have a getter! Throws when we try to set.
  _$0.C = _0;
}).call(this);

03.md

Input

var Cv = class C {
  constructor() {
    console.log(C === Cv);
  }
};

Output

var Cv;
(function() {
  var _$0 = this;

  var _0 = class {
    constructor() {
      console.log(C === Cv); // <------------ References `C`, but there is no class named `C`!
    }
  };

  _$0.Cv = _0;
}.call(this));

04.md

Input

class A {
  static get m() {}
}

Error

=== Diagnostics Log ===

Error: PP0022: a class method incorrectly went through the serializeValue() code path at 2:17 to 2:19

=== Compilation Failed ===

Error: A fatal error occurred while prepacking.
    at ResidualHeapSerializer.serializeValue (/Users/calebmer/prepack/lib/serializer/ResidualHeapSerializer.js:868:15)
    at ResidualHeapSerializer.emitDefinePropertyBody (/Users/calebmer/prepack/lib/serializer/ResidualHeapSerializer.js:506:109)
    at ResidualHeapSerializer._emitProperty (/Users/calebmer/prepack/lib/serializer/ResidualHeapSerializer.js:430:30)
    at emitter.emitNowOrAfterWaitingForDependencies (/Users/calebmer/prepack/lib/serializer/ResidualHeapSerializer.js:218:14)
    at Emitter.emitAfterWaiting (/Users/calebmer/prepack/lib/serializer/Emitter.js:435:9)
    at Emitter.emitNowOrAfterWaitingForDependencies (/Users/calebmer/prepack/lib/serializer/Emitter.js:492:10)
    at ResidualHeapSerializer._emitObjectProperties (/Users/calebmer/prepack/lib/serializer/ResidualHeapSerializer.js:215:20)
    at ResidualHeapSerializer._serializeClass (/Users/calebmer/prepack/lib/serializer/ResidualHeapSerializer.js:1360:10)
    at ResidualHeapSerializer._serializeValueFunction (/Users/calebmer/prepack/lib/serializer/ResidualHeapSerializer.js:1255:14)
    at ResidualHeapSerializer._serializeValueObjectBase (/Users/calebmer/prepack/lib/serializer/ResidualHeapSerializer.js:1744:18)
    at ResidualHeapSerializer._serializeValue (/Users/calebmer/prepack/lib/serializer/ResidualHeapSerializer.js:1700:19)
    at ResidualHeapSerializer.serializeValue (/Users/calebmer/prepack/lib/serializer/ResidualHeapSerializer.js:891:21)
    at nodes.args.map (/Users/calebmer/prepack/lib/utils/generator.js:126:58)
    at Array.map (<anonymous>)
    at TemporalBuildNodeEntry.serialize (/Users/calebmer/prepack/lib/utils/generator.js:126:29)
    at serializeFn (/Users/calebmer/prepack/lib/utils/generator.js:871:46)
    at Generator.serialize (/Users/calebmer/prepack/lib/utils/generator.js:880:7)
    at ResidualHeapSerializer.serialize (/Users/calebmer/prepack/lib/serializer/ResidualHeapSerializer.js:2001:20)
    at statistics.referenceCounts.measure (/Users/calebmer/prepack/lib/serializer/serializer.js:220:654)
    at PerformanceTracker.measure (/Users/calebmer/prepack/lib/statistics.js:91:14)
    at ast (/Users/calebmer/prepack/lib/serializer/serializer.js:219:38)
    at statistics.total.measure (/Users/calebmer/prepack/lib/serializer/serializer.js:230:9)
    at PerformanceTracker.measure (/Users/calebmer/prepack/lib/statistics.js:91:14)
    at Serializer.init (/Users/calebmer/prepack/lib/serializer/serializer.js:148:35)
    at prepackSources (/Users/calebmer/prepack/lib/prepack-standalone.js:71:33)
    at compileSource (/Users/calebmer/prepack/scripts/debug-fb-www.js:92:18)
    at compileFile (/Users/calebmer/prepack/scripts/debug-fb-www.js:129:31)
    at <anonymous>

05.md

Input

var date = new Date();
x = date + date;

…or:

x = typeof Date() === "string";

Error

=== Diagnostics Log ===

Error: PP0001: This operation is not yet supported on abstract value   at 2:11 to 2:15

=== Compilation Failed ===

Error: A fatal error occurred while prepacking.
    at AbstractValue.throwIfNotConcreteNumber (/Users/calebmer/prepack/lib/values/AbstractValue.js:506:11)
    at NativeFunctionValue.obj.defineNativeMethod.context [as callback] (/Users/calebmer/prepack/lib/intrinsics/ecma262/DatePrototype.js:574:49)
    at NativeFunctionValue.callCallback (/Users/calebmer/prepack/lib/values/NativeFunctionValue.js:85:51)
    at functionCall (/Users/calebmer/prepack/lib/methods/call.js:250:26)
    at callNativeFunctionValue (/Users/calebmer/prepack/lib/methods/call.js:276:10)
    at OrdinaryCallEvaluateBody (/Users/calebmer/prepack/lib/methods/call.js:282:12)
    at InternalCall (/Users/calebmer/prepack/lib/methods/function.js:80:49)
    at FunctionImplementation.$Call (/Users/calebmer/prepack/lib/methods/function.js:751:12)
    at NativeFunctionValue.$Call (/Users/calebmer/prepack/lib/values/NativeFunctionValue.js:25:36)
    at Call (/Users/calebmer/prepack/lib/methods/call.js:505:12)
    at ToImplementation.OrdinaryToPrimitiveOrAbstract (/Users/calebmer/prepack/lib/methods/to.js:587:37)
    at ToImplementation.OrdinaryToPrimitive (/Users/calebmer/prepack/lib/methods/to.js:561:17)
    at NativeFunctionValue.obj.defineNativeMethod [as callback] (/Users/calebmer/prepack/lib/intrinsics/ecma262/DatePrototype.js:619:27)
    at NativeFunctionValue.callCallback (/Users/calebmer/prepack/lib/values/NativeFunctionValue.js:85:51)
    at functionCall (/Users/calebmer/prepack/lib/methods/call.js:250:26)
    at callNativeFunctionValue (/Users/calebmer/prepack/lib/methods/call.js:276:10)
    at OrdinaryCallEvaluateBody (/Users/calebmer/prepack/lib/methods/call.js:282:12)
    at InternalCall (/Users/calebmer/prepack/lib/methods/function.js:80:49)
    at FunctionImplementation.$Call (/Users/calebmer/prepack/lib/methods/function.js:751:12)
    at NativeFunctionValue.$Call (/Users/calebmer/prepack/lib/values/NativeFunctionValue.js:25:36)
    at Call (/Users/calebmer/prepack/lib/methods/call.js:505:12)
    at ToImplementation.ToPrimitiveOrAbstract (/Users/calebmer/prepack/lib/methods/to.js:530:35)
    at Function.computeBinary (/Users/calebmer/prepack/lib/domains/ValuesDomain.js:128:34)
    at compute (/Users/calebmer/prepack/lib/evaluators/BinaryExpression.js:160:42)
    at computeBinary (/Users/calebmer/prepack/lib/evaluators/BinaryExpression.js:228:10)
    at _default (/Users/calebmer/prepack/lib/evaluators/BinaryExpression.js:49:10)
    at LexicalEnvironment.evaluateAbstract (/Users/calebmer/prepack/lib/environment.js:1185:20)
    at LexicalEnvironment.evaluate (/Users/calebmer/prepack/lib/environment.js:1173:20)
    at _default (/Users/calebmer/prepack/lib/evaluators/AssignmentExpression.js:48:22)
    at LexicalEnvironment.evaluateAbstract (/Users/calebmer/prepack/lib/environment.js:1185:20)
    at LexicalEnvironment.evaluate (/Users/calebmer/prepack/lib/environment.js:1173:20)
    at _default (/Users/calebmer/prepack/lib/evaluators/ExpressionStatement.js:23:21)
    at LexicalEnvironment.evaluateAbstract (/Users/calebmer/prepack/lib/environment.js:1185:20)
    at LexicalEnvironment.evaluate (/Users/calebmer/prepack/lib/environment.js:1173:20)
    at LexicalEnvironment.evaluateCompletion (/Users/calebmer/prepack/lib/environment.js:942:19)
    at LexicalEnvironment.evaluateCompletionDeref (/Users/calebmer/prepack/lib/environment.js:935:23)
    at _default (/Users/calebmer/prepack/lib/evaluators/Program.js:205:21)
    at LexicalEnvironment.evaluateAbstract (/Users/calebmer/prepack/lib/environment.js:1185:20)
    at LexicalEnvironment.evaluate (/Users/calebmer/prepack/lib/environment.js:1173:20)
    at _default (/Users/calebmer/prepack/lib/evaluators/File.js:25:15)
    at LexicalEnvironment.evaluateAbstract (/Users/calebmer/prepack/lib/environment.js:1185:20)
    at LexicalEnvironment.evaluate (/Users/calebmer/prepack/lib/environment.js:1173:20)
    at LexicalEnvironment.evaluateCompletion (/Users/calebmer/prepack/lib/environment.js:942:19)
    at res.realm.statistics.evaluation.measure (/Users/calebmer/prepack/lib/environment.js:1029:65)
    at PerformanceTracker.measure (/Users/calebmer/prepack/lib/statistics.js:91:14)
    at LexicalEnvironment.executeSources (/Users/calebmer/prepack/lib/environment.js:1029:46)
    at Serializer._execute (/Users/calebmer/prepack/lib/serializer/serializer.js:90:40)
    at statistics.total.measure (/Users/calebmer/prepack/lib/serializer/serializer.js:154:23)
    at PerformanceTracker.measure (/Users/calebmer/prepack/lib/statistics.js:91:14)
    at Serializer.init (/Users/calebmer/prepack/lib/serializer/serializer.js:148:35)
    at prepackSources (/Users/calebmer/prepack/lib/prepack-standalone.js:71:33)
    at compileSource (/Users/calebmer/prepack/scripts/debug-fb-www.js:92:18)
    at compileFile (/Users/calebmer/prepack/scripts/debug-fb-www.js:129:31)
    at <anonymous>

06.md

Input

"use strict";

var object = {
  *["a"]() {
    yield 1;
    yield 2;
  },
};

x = Object.keys(object);

Output

"use strict";

var x, object;
(function () {
  var _$0 = this;

  var _3 = function () {
    yield 1; // <---------------------------------- Yield outside of generator!
    yield 2;
  };

  _$0.object = {
    a: _3
  };
  _$0.x = ["a"];
}).call(this);

07.md

This is not a great example, but it uncovers an issue I saw a lot of: “all native function values should be intrinsics.” Our visitor expects that all FunctionValues which make it to visitValueFunction are not NativeFunctionValues since these should be intrinsics.

https://github.com/facebook/prepack/blob/b0516b49ea50d8ce81af6d0518e8ec071866201a/src/serializer/ResidualHeapVisitor.js#L1025-L1035

However, NativeFunctionValues may have an undefined intrinsicName. Which makes them not an intrinsic!

https://github.com/facebook/prepack/blob/b0516b49ea50d8ce81af6d0518e8ec071866201a/src/values/NativeFunctionValue.js#L36-L45

You can see an example of this here:

https://github.com/facebook/prepack/blob/e170c37aaa996c75cb166671c5b6af442a227d5c/src/intrinsics/ecma262/ObjectPrototype.js#L130-L163

Input

var ThrowTypeError = Object.getOwnPropertyDescriptor(
  (function() {
    "use strict";
    return arguments;
  })(),
  "callee"
).get;

ThrowTypeError(); // Expected to throw `TypeError`

Error

Invariant Violation: all native function values should be intrinsics
This is likely a bug in Prepack, not your code. Feel free to open an issue on GitHub.
    at invariant (/Users/calebmer/prepack/lib/invariant.js:24:15)
    at ResidualHeapVisitor.visitValueFunction (/Users/calebmer/prepack/lib/serializer/ResidualHeapVisitor.js:509:28)
    at _enqueueWithUnrelatedScope (/Users/calebmer/prepack/lib/serializer/ResidualHeapVisitor.js:1026:45)
    at _withScope (/Users/calebmer/prepack/lib/serializer/ResidualHeapVisitor.js:1255:19)
    at ResidualHeapVisitor._withScope (/Users/calebmer/prepack/lib/serializer/ResidualHeapVisitor.js:208:7)
    at runGeneratorAction (/Users/calebmer/prepack/lib/serializer/ResidualHeapVisitor.js:1254:18)
    at ResidualHeapVisitor._visitUntilFixpoint (/Users/calebmer/prepack/lib/serializer/ResidualHeapVisitor.js:1310:11)
    at ResidualHeapVisitor.visitRoots (/Users/calebmer/prepack/lib/serializer/ResidualHeapVisitor.js:1196:10)
    at statistics.deepTraversal.measure (/Users/calebmer/prepack/lib/serializer/serializer.js:195:68)
    at PerformanceTracker.measure (/Users/calebmer/prepack/lib/statistics.js:91:14)
    at ast (/Users/calebmer/prepack/lib/serializer/serializer.js:195:34)
    at statistics.total.measure (/Users/calebmer/prepack/lib/serializer/serializer.js:230:9)
    at PerformanceTracker.measure (/Users/calebmer/prepack/lib/statistics.js:91:14)
    at Serializer.init (/Users/calebmer/prepack/lib/serializer/serializer.js:148:35)
    at prepackSources (/Users/calebmer/prepack/lib/prepack-standalone.js:71:33)
    at compileSource (/Users/calebmer/prepack/scripts/debug-fb-www.js:92:18)
    at compileFile (/Users/calebmer/prepack/scripts/debug-fb-www.js:129:31)
    at <anonymous>

08.md

Input

var obj = {
  method() {
    return super.toString;
  },
};

obj.toString = null;

inspect = function() {
  return obj.method() === Object.prototype.toString;
};

Output

var obj;
(function () {
  var _$0 = this;

  var _2 = function () {
    return super.toString; // <------------------------------ `super` is not allowed here!
  };

  var _3 = function () {
    return obj.method() === Object.prototype.toString;
  };

  _$0.obj = {
    method: _2,
    toString: null
  };
  _$0.inspect = _3;
}).call(this);

09.md

TypedArray is a global not exposed to the user JavaScript runtime. Try global.TypedArray in your JavaScript environment of choice. We must emit Object.getPrototypeOf(Int8Array) instead of TypedArray.

Input

var TypedArray = Object.getPrototypeOf(Int8Array);
console.log(TypedArray.from.name === "from");

Output

var TypedArray;
(function() {
  var _$0 = this;

  var _$1 = _$0.TypedArray; // <-------------------- `TypedArray` is not exposed on the global object!
  _$0.TypedArray = _$1;
  console.log(true);
}.call(this));

10.md

Input

var TypedArray = Object.getPrototypeOf(Int8Array);
var TypedArrayPrototype = TypedArray.prototype;

Error

Invariant Violation:
This is likely a bug in Prepack, not your code. Feel free to open an issue on GitHub.
    at invariant (/Users/calebmer/prepack/lib/invariant.js:24:15)
    at ResidualHeapVisitor.visitValue (/Users/calebmer/prepack/lib/serializer/ResidualHeapVisitor.js:993:28)
    at ResidualHeapVisitor.visitEquivalentValue (/Users/calebmer/prepack/lib/serializer/ResidualHeapVisitor.js:987:10)
    at TemporalBuildNodeEntry.visit (/Users/calebmer/prepack/lib/utils/generator.js:105:82)
    at visitFn (/Users/calebmer/prepack/lib/utils/generator.js:855:46)
    at Generator.visit (/Users/calebmer/prepack/lib/utils/generator.js:863:7)
    at _withScope (/Users/calebmer/prepack/lib/serializer/ResidualHeapVisitor.js:1150:17)
    at ResidualHeapVisitor._withScope (/Users/calebmer/prepack/lib/serializer/ResidualHeapVisitor.js:208:7)
    at ResidualHeapVisitor.visitGenerator (/Users/calebmer/prepack/lib/serializer/ResidualHeapVisitor.js:1149:10)
    at ResidualHeapVisitor.visitRoots (/Users/calebmer/prepack/lib/serializer/ResidualHeapVisitor.js:1192:10)
    at statistics.deepTraversal.measure (/Users/calebmer/prepack/lib/serializer/serializer.js:195:68)
    at PerformanceTracker.measure (/Users/calebmer/prepack/lib/statistics.js:91:14)
    at ast (/Users/calebmer/prepack/lib/serializer/serializer.js:195:34)
    at statistics.total.measure (/Users/calebmer/prepack/lib/serializer/serializer.js:230:9)
    at PerformanceTracker.measure (/Users/calebmer/prepack/lib/statistics.js:91:14)
    at Serializer.init (/Users/calebmer/prepack/lib/serializer/serializer.js:148:35)
    at prepackSources (/Users/calebmer/prepack/lib/prepack-standalone.js:71:33)
    at compileSource (/Users/calebmer/prepack/scripts/debug-fb-www.js:92:18)
    at compileFile (/Users/calebmer/prepack/scripts/debug-fb-www.js:129:31)
    at <anonymous>