Don't hardcode linkage of default witness thunks, addressing a FIXME.
This will allow us to emit default witness thunks for requirements of
internal protocols, too.
Easy cut down on exported symbols. Unless a private type is referenced in
an inlineable function, there's no way to generate a reference to it
outside of the current file, except in the debugger. (That last bit is why
we can't use fully private linkage, which would keep the symbol out of the
symbol table completely.)
We should be doing this for "internal" declarations as well, but the
standard library /does/ have references to internal types in inlineable
functions, and also has tests that directly access these types.
Swift SVN r24838
Teach IRGen to honor the linkage of SILWitnessTables, and teach SILGen to emit witness tables and protocol witness thunks for external definitions with shared linkage. Fixes <rdar://problem/16264703>.
Swift SVN r14908
In general, this forces SILGen and IRGen code that's grabbing
a declaration to state whether it's doing so to define it.
Change SIL serialization to serialize the linkage of functions
and global variables, which means also serializing declarations.
Change the deserializer to use this stored linkage, even when
only deserializing a declaration, and to call a callback to
inform the client that it has deserialized a new entity.
Take advantage of that callback in the linking pass to alter
the deserialized linkage as appropriate for the fact that we
imported the declaration. This computation should really take
advantage of the relationship between modules, but currently
it does not.
Swift SVN r12090
