After this change,
extension P where WHERE1 { final func foo() {} }
extension P where WHERE2 { final func bar() { #^COMPLETE_HERE^#
will complete foo() if and only if WHERE2 is complatible with WHERE1.
Swift SVN r27480
Most tests were using %swift or similar substitutions, which did not
include the target triple and SDK. The driver was defaulting to the
host OS. Thus, we could not run the tests when the standard library was
not built for OS X.
Swift SVN r24504
