Foundation URL Improvements

[Saklad5 (Jeremy Saklad)]

@Karl

This is a nice addition, although I have some questions:

• The description says it will assert , but do you actually mean fatalError ? What happens in a release build if the string cannot be parsed?
• If you're doing this for string literals, why not go all the way and make it ExpressibleByStringLiteral ?

The convention is:

• Swift.assert(_:_:file:line:) is used for serious errors by the programmer
• Swift.precondition(_:_:file:line:) is used for serious errors by other programmers (as the name implies, mainly violated preconditions)
• Swift.fatalError(_:file:line:) (and forced unwrapping) is used for serious errors that aren’t the result of programmer error.

By requiring StaticString, the new initializer forces invalid input to fall into the first two categories. It arguably belongs in the second category, but the benefit of skipping assertion checks entirely in release builds probably justifies that.

Personally, I’ve been using Swift.Optional.unsafelyUnwrapped for hard-coded URLs, which has very similar behavior to assertions.