This function now takes an optional out parameter for callers who would
like to what kind of property we ended up getting.
This will be used to implement inline caching for property lookups.
Also, to prepare for adding more forms of caching, the out parameter
is a struct CacheablePropertyMetadata rather than just an offset. :^)
Note that as of this commit, there aren't any such throwers, and the
call site in Heap::allocate will drop exceptions on the floor. This
commit only serves to change the declaration of the overrides, make sure
they return an empty value, and to propagate OOM errors frm their base
initialize invocations.
This is a continuation of the previous commit.
Calling initialize() is the first thing that's done after allocating a
cell on the JS heap - and in the common case of allocating an object,
that's where properties are assigned and intrinsics occasionally
accessed.
Since those are supposed to live on the realm eventually, this is
another step into that direction.
No functional changes - we can still very easily get to the global
object via `Realm::global_object()`. This is in preparation of moving
the intrinsics to the realm and no longer having to pass a global
object when allocating any object.
In a few (now, and many more in subsequent commits) places we get a
realm using `GlobalObject::associated_realm()`, this is intended to be
temporary. For example, create() functions will later receive the same
treatment and are passed a realm instead of a global object.
Now that the Object rewrite is in place, we have enough tools to
implement the mapped `arguments` propreties according to spec.
The basic mechanism is that the `arguments` object installs a hidden
parameter mapping object that property accesses get filtered through.
This is how accessing numeric properties on `arguments` are proxied
to the named identifier in the function scope.
When `arguments` is instantiated, getters and setters are created
for all the numeric properties on the object that correspond to
function arguments. These getters and setters can be deleted from the
object. This is all pretty intricate, so refer to the spec for details.
Note that the `arguments` object itself is still lazily instantiated
on first access within a function. This is non-conforming, and we'll
have to revisit this once we get around to improving function calls.
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`.
