This is an implementation of 'The Property Descriptor Specification
Type' and related abstract operations, namely:
- IsAccessorDescriptor
- IsDataDescriptor
- IsGenericDescriptor
- FromPropertyDescriptor
- ToPropertyDescriptor
- CompletePropertyDescriptor
It works with Optional<T> to enable omitting certain fields, which will
eventually replace the Attribute::Has{Getter,Setter,Configurable,
Enumerable,Writable} bit flags, which are awkward to work with - being
able to use an initializer list with any of the possible attributes is
much more convenient.
Parts of the current PropertyAttributes implementation as well as the
much simpler PropertyDescriptor struct in Object.h will eventually be
replaced with this and completely go away.
Property storage will still use the PropertyAttributes bit flags, this
is for the layers above.
Note that this is currently guarded behind an #if 0 as if conflicts with
the existing PropertyDescriptor struct, but it's known to compile and
work just fine - I simply want to have this in a separate commit, the
primary object rewrite commit will be large enough as is.
Specifically, explicitly specify the checked type, use the resulting
value instead of doing the same calculation twice, and break down
calculations to discrete operations to ensure no intermediary overflows
are missed.
Specifically, this now explicitly takes the length, adds missing
exceptions checks to calls with user-supplied lengths, takes and uses
the prototype argument, and fixes some spec non-conformance in
ArrayConstructor and its native functions around the use of ArrayCreate
This patch implements spec-compliant runtime semantics for the following
constructs:
- super.property
- super[property]
The MakeSuperPropertyReference AO is added to support this. :^)
ResolveBinding now matches the spec, while the non-conforming parts
are moved to GetIdentifierReference.
Implementing this properly requires variable bindings.
This is used by VM::call_internal() and VM::construct() which roughly
map to function objects' [[Call]] and [[Construct]] slots in the spec.
Reorganizing this code revealed something weird: NativeFunction gets
its strictness by checking VM::in_strict_mode(). In other words,
it inherits the strict flag from the caller context. This is quite
weird, but many test-js tests rely on it, so let's preserve it until
we can think of something nicer.
Specifically, instead of using the internal {get, put}_by_index methods
we now use the GetValueFromBuffer and SetValueInBuffer abstract
operations, as required by the specification.
While i was here i also replaced a couple custom detached array buffer
error messages with the existing ErrorType::DetachedArrayBuffer.
This should really be handled at a different layer of the stack, but
this allows us to make progress on the Object rewrite without breaking
strict mode assignment tests.
This code is non-conforming and will eventually get cleaned out once
we implement proper variable bindings. However, this will aid us in
improving other parts of the code right now.
This PR does not fix the main issue with our current implementation:
The specification requires that we first check the JSON string for
validity with an ECMA-404 compliant parser, and then evaluate it as if
it was javascript code, of which we do neither at the moment.
Specifically, we now cast to a u32 instead of an i32, as well as use
the validity check required by the specification. The current
constructor is still quite far from the specification, as we directly
set the indexed properties' length instead of going through the Array's
overriden DefineOwnProperty. (and as a result the checks imposed by the
ArraySetLength abstract operation)
This is not exactly compliant with the specification, but our current
bound function implementation isn't either, so its not currently
possible to implement it the way the specification requires.
This patch adds a new ArgumentsObject class to represent what the spec
calls "Arguments Exotic Objects"
These are constructed by the new CreateMappedArgumentsObject when the
`arguments` identifier is resolved in a callee context.
The implementation is incomplete and doesn't yet support mapping of
the parameter variables to the indexed properties of `arguments`.
This includes checking that the target is a constructor, not just a
function, as well as switching the order of the list creation and
argument validation to match the specification, to ensure correct
exception throwing order.
This patch implements the IsSimpleParameterList static semantics for
ordinary function objects.
We now also create an unmapped arguments object for callee contexts
with non-simple parameter lists, instead of only doing it in strict
mode. Covered by test262.
This makes the implicit run-time assertion in PropertyName::to_string()
into an explicit compile-time requirement, removes a wasteful FlyString
-> PropertyName -> FlyString construction from NativeFunction::create()
and allows setting the function name to a null string for anonymous
native functions.
The unsigned shift right implementation was already doing this, but
the spec requires a mod32 of rhs before the shift for the signed shift
right implementation as well. Caught by UBSAN and oss-fuzz.
If the value we get after fmod in Value::to_u32 is negative, UBSAN
complains that -N is out of bounds for u32. An extra static cast to i64
makes it stop complaining. An alternative implementation could add 2^32
if the fmod'd value is negative. Caught by UBSAN and oss-fuzz.
