conform to LogicValue.
This approach was taken to keep _isNull because I first tried
to just use comparisons to nil instead of isNull(). Apparently
that led to some circular definitions, so it was easier to just
stage it this way.
Swift SVN r18301
The runtime implementation of 'as T' freaks out in cases involving protocols. This is an expedient workaround that fixes <rdar://problem/16950035>.
Swift SVN r18263
assert() and fatalError()
These functions are meant to be used in user code. They are enabled in debug
mode and disabled in release or fast mode.
_precondition() and _preconditionFailure()
These functions are meant to be used in library code to check preconditions at
the api boundry. They are enabled in debug mode (with a verbose message) and
release mode (trap). In fast mode they are disabled.
_debugPrecondition() and _debugPreconditionFailure()
These functions are meant to be used in library code to check preconditions that
are not neccesarily comprehensive for safety (UnsafePointer can be null or an
invalid pointer but we can't check both). They are enabled only in debug mode.
_sanityCheck() and _fatalError()
These are meant to be used for internal consistency checks. They are only
enabled when the library is build with -DSWIFT_STDLIB_INTERNAL_CHECKS=ON.
I modified the code in the standard library to the best of my judgement.
rdar://16477198
Swift SVN r18212
