The unarchiveTopLevelObjectWithData which returns Any? (instead of
AnyObject?) was added in Swift 4 and has only shipped in the betas so
far. Instead of adding new overloads which take different types, we
should just fix this one and call it a day.
We missed a few NSKeyedUnarchiver methods during our original renaming
for Swift — some of these methods still take NSData when they can take
Data. We can add Data variants which bridge to NSData to fix this in a
backwards-compatible way.
This avoids indirection by making calls directly to the C implementations which prevents potentials of mismatched intent or changes of calling convention of @_silgen. The added benefit is that all of the shims in this case are no longer visible symbols (anyone using them was not authorized out side of the Foundation overlay). Also the callout methods in the headers now all share similar naming shcemes for easier refactoring and searching in the style of __NS<class><action> style. The previous compiled C/Objective-C source files were built with MRR the new headers MUST be ARC by Swift import rules.
The one caveat is that certain functions MUST avoid the bridge case (since they are part of the bridging code-paths and that would incur a recursive potential) which have the types erased up to NSObject * via the macro NS_NON_BRIDGED.
The remaining @_silgen declarations are either swift functions exposed externally to the rest of Swift’s runtime or are included in NSNumber.gyb which the Foundation team has other plans for removing those @_silgen functions at a later date and Data.swift has one external function left with @_silgen which is blocked by a bug in the compiler which seems to improperly import that particular method as an inline c function.
