src/third_party/v8/src/builtins/object-fromentries.tq

// Copyright 2018 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

namespace object {

transitioning macro ObjectFromEntriesFastCase(implicit context: Context)(
    iterable: JSAny): JSObject labels IfSlow {
  typeswitch (iterable) {
    case (array: FastJSArrayWithNoCustomIteration): {
      const elements: FixedArray =
          Cast<FixedArray>(array.elements) otherwise IfSlow;
      const length: Smi = array.length;
      const result: JSObject = NewJSObject();

      for (let k: Smi = 0; k < length; ++k) {
        const value: JSAny = array::LoadElementOrUndefined(elements, k);
        const pair: KeyValuePair =
            collections::LoadKeyValuePairNoSideEffects(value)
            otherwise IfSlow;
        // Bail out if ToPropertyKey will attempt to load and call
        // Symbol.toPrimitive, toString, and valueOf, which could
        // invalidate assumptions about the iterable.
        if (Is<JSReceiver>(pair.key)) goto IfSlow;
        FastCreateDataProperty(result, pair.key, pair.value);
      }
      return result;
    }
    case (JSAny): {
      goto IfSlow;
    }
  }
}

transitioning javascript builtin
ObjectFromEntries(
    js-implicit context: NativeContext, receiver: JSAny)(...arguments): JSAny {
  const iterable: JSAny = arguments[0];
  try {
    if (IsNullOrUndefined(iterable)) goto Throw;
    return ObjectFromEntriesFastCase(iterable) otherwise IfSlow;
  } label IfSlow {
    const result: JSObject = NewJSObject();
    const fastIteratorResultMap: Map = GetIteratorResultMap();
    let i: iterator::IteratorRecord = iterator::GetIterator(iterable);
    try {
      assert(!IsNullOrUndefined(i.object));
      while (true) {
        const step: JSReceiver =
            iterator::IteratorStep(i, fastIteratorResultMap)
            otherwise return result;
        const iteratorValue: JSAny =
            iterator::IteratorValue(step, fastIteratorResultMap);
        const pair: KeyValuePair = collections::LoadKeyValuePair(iteratorValue);
        FastCreateDataProperty(result, pair.key, pair.value);
      }
      return result;
    } catch (e) deferred {
      iterator::IteratorCloseOnException(i);
      ReThrow(context, e);
    }
  } label Throw deferred {
    ThrowTypeError(MessageTemplate::kNotIterable);
  }
}
}  // namespace object