Understanding switch + foreach

[Steven Schveighoffer]

On Thu, 17 Apr 2014 06:54:39 -0400, Timon Gehr <timon.gehr at gmx.ch> wrote:

> On 04/08/2014 05:14 PM, Steven Schveighoffer wrote:
>> On Mon, 07 Apr 2014 18:30:30 -0400, Matej Nanut <matejnanut at gmail.com>
>> wrote:
>>
>>> Hello,
>>>
>>> I don't understand why so many break statements are needed in this
>>> construct:
>>>
>>>     immutable key = 3;
>>>     switch (key)
>>>     {
>>>         foreach (c; TypeTuple!(1, 2, 3, 4, 5))
>>>         {
>>>             case c: "Found %s!".writefln(c);
>>>                     break;
>>>         }
>>>         break; // Default always gets executed without this break.
>>>         default:
>>>             "Not found %s :(".writefln(key);
>>>             break;
>>>     }
>>>
>>> One after each case and another one after the foreach.
>>
>> First, let me say this is a cool usage of compile-time foreach, I had
>> never thought of that.
>> ...
>
> I do this quite often.

You get a gold star then ;)

>
>> Second, I think the issue is likely a bug with the break exiting the
>> wrong scope.
>
> No, this is expected behaviour. break and continue work in any foreach  
> statement. break always breaks the innermost breakable statement. (In  
> particular, it does not pair up with case statements.)

But should a foreach over a tuple a breakable statement? Basically, the  
above seems to me it should be equivalent to:

case 1:
    writefln("Found %s!", 1);
    break;
case 2:
    writefln("Found %s!", 2);
    break;
...

The foreach should be gone once the foreach is executed at compile-time.

If the break breaks the foreach, why isn't just case 1 produced? That  
would be an actual break in the foreach, no?

-Steve