After reading the Ray Wenderlich website tutorial  about Unsafe Swift, I
was checking out this file  inside swift/stdlib/public/core titled
MemoryLayout.swift. However, I was confused about the @_transparent before
the each data member inside the enum. Why is this enum with the data
members allowed by the Swift 3 language? What does @_transparent allow you
to do that you might not otherwise? Could someone explain because the
documentation is still unclear ?