[swift-evolution] URL Literals

[Micah Hainline]

I would like to be able to create a URL literal that is compile-time
checked for correct format. This would help avoid code like this:

    let url: URL = URL(string: "https://example.com")!

The cleanest way I can think of doing that would be to introduce a new
macro structure similar to #selector, though I'm open to other ideas.
I would think it should take a quoted literal string to avoid
problems. That would look like this:

    let url: URL = #url("https://example.com")

What does everyone think of that idea?