Expose a method on built-in iterators that allows retrieving the next
iteration result without allocating a JS::Object. This change is a
preparation for optimizing for..of and for..in loops.
This is a normative change in the ECMA-262 spec. See:
de62e8d
This did not actually seem to affect our implementation as we were not
using generators here to begin with. So this patch is basically just
adding spec comments.
Resulting in a massive rename across almost everywhere! Alongside the
namespace change, we now have the following names:
* JS::NonnullGCPtr -> GC::Ref
* JS::GCPtr -> GC::Ptr
* JS::HeapFunction -> GC::Function
* JS::CellImpl -> GC::Cell
* JS::Handle -> GC::Root
With the addition of symbol keys, work can now be done on starting to
implement the well-known symbol functionality. The most important of
these well-known symbols is by far Symbol.iterator.
This patch adds IteratorPrototype, as well as ArrayIterator and
ArrayIteratorPrototype. In the future, sometime after StringIterator has
also been added, this will allow us to use Symbol.iterator directly in
for..of loops, enabling the use of custom iterator objects. Also makes
adding iterator support to native objects much easier (as will have to
be done for Map and Set, when they get added).
