Design concerns for borrowing and inout pattern matching

[xwu (Xiaodi Wu)]

@jeremyabannister

To me this seems unclear because you might think isEven would only be usable from within extensions on Int.

That would be a misunderstanding of private: it refers to the lexical scope in which it's written, which in this case is the file scope. In fact this use of private extension, with the addition of support for stored properties in same-file extensions, is the only way in which the envisioned removal of fileprivate would be possible.