[swift-dev] ExistentialMetatypeType assertion failure on Linux

[Luke Howard]

> On 31 Dec 2015, at 11:25 AM, Luke Howard via swift-dev <swift-dev at swift.org> wrote:
> 
>> I really want to merge in the rest of the coders; so lets go ahead and omit the mangling stuff and leave it just as the Foundation classes . That will be a huge win in my book, it gives us something that is testable and functional enough to do some pretty impressive demonstrations of archiving.
> 
> OK, the version I’ve pushed now removes the code that was poking into runtime structures but still uses dlopen()/the metadata accessor for NSClassFromString(). Tests verify on OS X and Linux (with compiler fix).
> 
> If you want to change this further to use a static mapping table, go for it, but I’d rather focus my time on getting the appropriate API into stdlib.

As a compromise how about a:

* swift_getTypeByName() API that only takes demangled names
* NSClassFromString()/NSStringFromClass() remain internal and hard fail with nested classes/generics
* We decide what to do about nested class interop later (is changing the Darwin behaviour something that would even be on the table?)

— Luke