request switch statement with common block

[Andre Artus]

>> As Andrei points out in his book ("The D Programming 
>> Language") contracts are not used to validate/scrub user (or 
>> any external) input as they can be compiled out of the 
>> executable.
>>
>> Contracts are there to check sanity at compile time, or at the 
>> very least during testing.
>>
>> The contract is (or should be) part of the documentation.
>
> You are correct. I will have to check out his book.

Be sure to check out the errata page
http://erdani.com/tdpl/errata/