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LibJS: Add spec comments to Value::to_index()

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This commit is contained in:
Linus Groh 2022-12-10 00:03:10 +00:00
parent d1b2ac41fd
commit 72ee346f64
1 changed files with 25 additions and 6 deletions
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31
Userland/Libraries/LibJS/Runtime/Value.cpp
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@ -1090,15 +1090,34 @@ ThrowCompletionOr<size_t> Value::to_length(VM& vm) const
// 7.1.22 ToIndex ( argument ), https://tc39.es/ecma262/#sec-toindex // 7.1.22 ToIndex ( argument ), https://tc39.es/ecma262/#sec-toindex
ThrowCompletionOr<size_t> Value::to_index(VM& vm) const ThrowCompletionOr<size_t> Value::to_index(VM& vm) const
{ {
if (is_undefined()) // 1. If value is undefined, then
if (is_undefined()) {
// a. Return 0.
return 0; return 0;
auto integer_index = TRY(to_integer_or_infinity(vm)); }
if (integer_index < 0)
// 2. Else,
// a. Let integer be ? ToIntegerOrInfinity(value).
auto integer = TRY(to_integer_or_infinity(vm));
// OPTIMIZATION: If the value is negative, ToLength normalizes it to 0, and we fail the SameValue comparison below.
// Bail out early instead.
if (integer < 0)
return vm.throw_completion<RangeError>(ErrorType::InvalidIndex); return vm.throw_completion<RangeError>(ErrorType::InvalidIndex);
auto index = MUST(Value(integer_index).to_length(vm));
if (integer_index != index) // b. Let clamped be ! ToLength(𝔽(integer)).
auto clamped = MUST(Value(integer).to_length(vm));
// c. If SameValue(𝔽(integer), clamped) is false, throw a RangeError exception.
if (integer != clamped)
return vm.throw_completion<RangeError>(ErrorType::InvalidIndex); return vm.throw_completion<RangeError>(ErrorType::InvalidIndex);
return index;
// d. Assert: 0 ≤ integer ≤ 2^53 - 1.
VERIFY(0 <= integer && integer <= MAX_ARRAY_LIKE_INDEX);
// e. Return integer.
// NOTE: We return the clamped value here, which already has the right type.
return clamped;
} }
// 7.1.5 ToIntegerOrInfinity ( argument ), https://tc39.es/ecma262/#sec-tointegerorinfinity // 7.1.5 ToIntegerOrInfinity ( argument ), https://tc39.es/ecma262/#sec-tointegerorinfinity