Extend the previous commit’s support for functions that return Never to also properly generate code for *throwing* Never functions. This is a little subtle because:
• At the SWIFT_CALL level, throwing Never functions are *not* noreturn
• At the thunk level, throwing Never functions are noreturn *only* if you’re using exceptions; if you’re using swift::Expected, they should throw
• In either case, the compiler cannot statically prove that thunks are noreturn except on the error path, so we need to add an abort() call on the success path
This allows easier use and more wider API exposure from the Swift stdlib
In the future, all functions and method should incorporate argument labels, but it's not yet clear how
This macro applies always_inline in addition to inline. It also applies artificial, which lets debugger know that this is an artificial function. The used attribute is added in debug builds to ensure that the symbol is emitted in the binary so that LLDB can invoke it.
This is done by exposing nested Index and UTF8View type in String. Nested types aren't
supported yet, so we need to employ a number of hacks to emit them.
