Being really close to Object.prototype.valueOf() name wise makes this
unnecessarily confusing - while it sometimes serves as the
implementation of a valueOf() function, it's an abstraction which the
spec doesn't have.
Use the appropriate getters to retrieve specific internal slots instead,
most commonly [[FooData]] from the primitive wrapper objects.
For the Object class specifically, use the Value(Object*) ctor instead.
This commit adds support for the most bare bones version of async
functions, support for async generator functions, async arrow functions
and await expressions are TODO.
By replacing this VERIFY with a thrown Error we no longer crash when
calling a generator function in the AST interpreter. This allows us to
more gracefully handle situation which have not been implemented yet.
In particular this helps the libjs-test262-runner since it can now
continue on to the next tests instead of having the entire process end.
This one is a bit unusual, so to clarify:
Previously, callers of get_iterator_values() would supply a callback
that would return an IterationDecision, and an enum to indicate whether
iterator_close() should be invoked upon IterationDecision::Break.
Now, use of both those enums is removed, and callers must return an
Optional<Completion>. If a Completion is provided, the iterator will be
closed, and that completion will be returned from get_iterator_values.
Otherwise, once the iterator is exhausted, a default-initialized
Completion will be returned.
This is necessary as we might have to perform named evaluation with the
field name.
Ideally we would also skip some setup parts of the function like
function_declaration_instantiation however this would require bigger
changes to ECMAScriptFunctionObject.
This patch implements:
- Spec compliant [[Call]] and [[Construct]] internal slots, as virtual
FunctionObject::internal_{call,construct}(). These effectively replace
the old virtual FunctionObject::{call,construct}(), but with several
advantages:
- Clear and consistent naming, following the object internal methods
- Use of completions
- internal_construct() returns an Object, and not Value! This has been
a source of confusion for a long time, since in the spec there's
always an Object returned but the Value return type in LibJS meant
that this could not be fully trusted and something could screw you
over.
- Arguments are passed explicitly in form of a MarkedValueList,
allowing manipulation (BoundFunction). We still put them on the
execution context as a lot of code depends on it (VM::arguments()),
but not from the Call() / Construct() AOs anymore, which now allows
for bypassing them and invoking [[Call]] / [[Construct]] directly.
Nothing but Call() / Construct() themselves do that at the moment,
but future additions to ECMA262 or already existing web specs might.
- Spec compliant, standalone Call() and Construct() AOs: currently the
closest we have is VM::{call,construct}(), but those try to cater to
all the different function object subclasses at once, resulting in a
horrible mess and calling AOs with functions they should never be
called with; most prominently PrepareForOrdinaryCall and
OrdinaryCallBindThis, which are only for ECMAScriptFunctionObject.
As a result this also contains an implicit optimization: we no longer
need to create a new function environment for NativeFunctions - which,
worth mentioning, is what started this whole crusade in the first place
:^)
Most switch statements don't have any lexically scoped declarations,
so let's avoid allocating an environment in the common case where we
don't have to.
This commit partially reverts "LibJS: Make accessing the current
function's arguments cheaper".
While the change passed all the currently passing test262 tests, it
seems to have _some_ flaw that silently breaks with some real-world
websites.
As the speedup with negligible at best, let's just revert it until we
can implement it more correctly.
We now propagate this flag to FunctionDeclaration, and then also into
ECMAScriptFunctionObject.
This will be used to disable optimizations that aren't safe in the
presence of direct eval().
Instead of going through an environment record, make arguments of the
currently executing function generate references via the argument index,
which can later be resolved directly through the ExecutionContext.
