swift

f0e7ff68 - [Backtracing] Add a precondition to protect against problems in future.

[Backtracing] Add a precondition to protect against problems in future. Because the cache uses the page addresses as its keys, we should have a precondition to check that we haven't passed an address within a page. The latter would result in confusing behaviour so it's worth diagnosing up front. rdar://117681625