Add the ability to store optionality of the ObjC method parameters and return
type in a sidecar. This hardcoded info is then used to import Objective C
object pointer types as either optional or none, instead of implicitly
unwrapped optionals.
The feature is enabled with -import-with-tighter-objc-types=true.
Swift SVN r19048
...in preparation for non-source locations, i.e. locations that don't come
frome source buffers.
No functionality change, but a fair bit of SourceManager API and idioms have
changed.
Swift SVN r18942
-Hide vars that have a private type.
-Hide functions that have a parameter with private type or a parameter name with leading underscore.
-Minor change in StringUTF16.swift to avoid printing "func generate() -> IndexingGenerator<_StringCore>".
rdar://17027294
Swift SVN r18623
