This code got refactored and it accidentally widened the applicable structures for this check. The idea is that you have the following structure
// Module A
@_weakLinked import B
// Module B
@_exported import C
And the compiler conspires to make it so the modules B AND C wind up weak-linked from module A.
The broadened check accidentally allowed the following:
// Module A
@_weakLinked import B
// Module B
import C // Oops!
Which caused quite a few more modules than were intended to be weak-linked. Restore the `Exported` filter to cut back on the amount of weak re-exports the compiler processes.
Resolves rdar://142706779
