Elaborate on destructuring syntax in match

[ledoge]

In the old version of the book, it is mentioned that : can be used to give a value a new name under 4.15. I found this misleading because it is never mentioned that : is just a part of the pattern that can also be used for testing values.

For the new book, I think it would be good to use a more complex example of destructuring and explain its syntax. I would have found an example like in this blog post very useful for understanding the possible uses:

       GuessState { answer: Answer::Bingo, guess: p, .. } => {
     // ~~~~~~~~~~   ~~~~~~~~~~~~~~~~~~~~~  ~~~~~~~~  ~~
     //     |                 |                 |     |
     //     |                 |                 |     Ignore remaining fields
     //     |                 |                 |
     //     |                 |      Copy value of field `guess` into local variable `p`
     //     |                 |
     //     |   Test that `answer field is equal to `Bingo`
     //     |
     //  Match against an instance of the struct `GuessState````

[nodakai]

Cool illustration. But please do your best to keep the book accessible to our visually impaired fellows. Cf.

• http://stackoverflow.com/questions/118984/how-can-you-program-if-youre-blind
• http://www.huffingtonpost.com/quora/how-do-blind-computer-pro_b_7163674.html
• Accessibility in package search, listing, and display crates.io#173

[carols10cents]

@nodakai don't worry, @ledoge was just providing an example of what they were looking for. I found their example very helpful, and in the commit linked to this issue that I made before your comment, you'll see that we did not use the example with the ascii annotations.