[swift-evolution] [Pitch] Introduce continue to switch statements

[Erica Sadun]

> On Jul 10, 2016, at 10:16 PM, Xiaodi Wu <xiaodi.wu at gmail.com> wrote:
> Given patterns A, B, C, and D, suppose a value x matches A, C, and D, whereas another value y matches B and D, and a third value matches B and C. When evaluating x, y, or z, which statements are executed in the following switch statement? How many of these reach the default case? What happens if I append `fallthrough` at the end of case D? What happens if I move case B after case D? (Yes, I know it is possible to figure it out [my understanding of the answer to the first question is appended below], but I hope you'll agree with me that this is much more difficult to decipher than any switch statement that's currently possible.)
> 
> ```
> switch x /* or y, or z */ {
> case A:
>   // ...
>   continue
> case B:
>   // ...
>   if C ~= x /* or y, or z, whichever is switched over */ {
>     continue
>   }
>   fallthrough

I'd say it would be fair to disallow continue and fallthrough to occur in the same clause

> case C:
>   // ...
>   if B ~= x /* or y, or z, whichever is switched over */ {
>     continue
>   }
> case D:
>   // ...
> default:
>   // ...
> }
> ```

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