There is no such thing as a "undefined literal" in JS - undefined is
just a property on the global object with a value of undefined.
This is pretty similar to NaN.
var undefined = "foo"; is a perfectly fine AssignmentExpression :^)
This patch adds JS::Shape, which implements a transition tree for our
Object class. Object property keys, prototypes and attributes are now
stored in a Shape, and each Object has a Shape.
When adding a property to an Object, we make a transition from the old
Shape to a new Shape. If we've made the same exact transition in the
past (with another Object), we reuse the same transition and both
objects may now share a Shape.
This will become the foundation of inline caching and other engine
optimizations in the future. :^)
Let's move towards using references over pointers in LibJS as well.
I had originally steered away from it because that's how I've seen
things done in other engines. But this is not the other engines. :^)
This adds Function::construct() for constructor function calls via `new`
keyword. NativeFunction doesn't have constructor behaviour by default,
ScriptFunction simply calls call() in construct()
LibWeb now creates a WindowObject which inherits from GlobalObject.
Allocation of the global object is moved out of the Interpreter ctor
to allow for specialized construction.
The existing Window interfaces are moved to WindowObject with their
implementation code in the new Window class.
These functions allow us to try to parse ambiguous expressions (such as
arrow function arguments in parentheses), and
rewind the state of the Parser if an expression candidate failed to
parse.
This adds:
- A global Date object (with `length` property and `now` function)
- The Date constructor (no arguments yet)
- The Date prototype (with `get*` functions)
- An empty string is converted to 0
- An empty array is converted to 0
- An array with one item is converted to that item's numeric value
- An array with more than one item is converted to NaN
Instead of implementing every native function as a lambda function,
use static member functions instead.
This makes it easier to navigate the code + backtraces look nicer. :^)
Native functions now only get the Interpreter& as an argument. They can
then extract |this| along with any indexed arguments it wants from it.
This forces functions that want |this| to actually deal with calling
interpreter.this_value().to_object(), and dealing with the possibility
of a non-object |this|.
This is still not great but let's keep massaging it forward.
Fix the "instanceof" operator to check if the constructor's prototype
property occurs anywhere in the prototype chain of the instance object.
This patch also adds Object.setPrototypeOf() to make it possible to
create a test for this bug.
Thanks to DexesTTP for pointing this out! :^)
This operator walks the prototype chain of the RHS value and looks for
a "prototype" property with the same value as the prototype of the LHS.
This is pretty cool. :^)
NewExpression mostly piggybacks on the existing CallExpression. The big
difference is that "new" creates a new Object and passes it as |this|
to the callee.
Unary expressions parsing now respects precedence and associativity of
operators. This patch also makes `typeof` left-associative which was
an oversight.
Thanks to Conrad for helping me work this out. :^)
