This is hidden behind the frontend flag -enable-objc-optional. Use -Xfrontend
when invoking the Swift driver.
Part of <rdar://problem/15189135>
Swift SVN r14332
Added a new ClangImporterOptions class which wraps the ModuleCachePath and ExtraArgs for the Clang importer.
Added a new ParseClangImporterArgs static function which fills in the passed-in ClangImporterOptions.
Updated CompilerInvocation and CompilerInvocation::parseArgs() to use ClangImporterOptions and ParseClangImporterArgs, respectively.
Swift SVN r11180