Cocoa allows objects to override -isKindOfClass: to lie about their class.
As bad as it is, Swift should respect that. <rdar://problem/13013432>
Note that this clashes with the SWIFT_DISABLE_SWIFT_BIT_ON_CLASS_DATA hack;
on 10.9 -isKindOfClass: will always be used. In the long run, we don't
really want to ask if the target /type/ is an Objective-C type, but rather
if the target /object/ is an Objective-C object.
Swift SVN r3911
Introduce a new swift_dynamicCast pair that take in a general metatype
pointer, rather than the more specific class-metatype pointer used for
class downcasts, and grab the class out of that general metatype
pointer, which may actually be an Objective-C wrapper. This is
slightly slower, but it works for the super-to-archetype cases like
T(an_NSObject), where T can have either kind of metadata.
NSTypedArray<T> is actually run-time type checked now, yay!
Swift SVN r3564
This variant of swift_dynamicCast requires us to have data that's
guaranteed to be class metadata, but it's not always natural to
generate class metadata. No functionality change yet.
Swift SVN r3562
We add a new runtime entry point, swift_dynamicCastUnconditional(),
that aborts when the cast fails. We'll probably want to throw an
exception in the future, but this is fine for now.
Swift SVN r3554
Notably, there is still no support for +1 return values,
so we'll leak when doing alloc/init and so on; but this gets
the fundamentals in place. A lot of the extra stuff in here
is dealing with mapping between metatypes and class objects.
Swift SVN r3425
The interesting thing here is that we need runtime support in
order to generate references to metatypes for classes, mostly
because normal ObjC classes don't have all the information we want
in a metatype (which for now just means the VWT pointer).
We'll need to be able to reverse this mapping when finding a
class pointer to hand off to, say, an Objective-C class method,
of course.
Swift SVN r3424
