assert() vs. enforce(), invariant() vs. ... ?

[Artur Skawina]

On 08/29/13 16:55, Joseph Rushton Wakeling wrote:
> On 29/08/13 16:21, Artur Skawina wrote:
>> In order to handle ref-returns it would have to be more like
>>
>>     struct EnforceWrapper(T) {
>>        T t;
>>
>>        auto ref opDispatch(string M, Args...)(Args args) {
>>           {/*before code*/}
>>           scope (exit) {/*after code*/}
>>           return mixin("t." ~ M ~ "(args)");
>>        }
>>     }
>>
>> and need another two overloads for property/field getters and
>> setters. Handling ref-args would add more complexity, but in
>> many cases ignoring them or using auto-ref is enough.
> 
> Interesting.  When it comes down to it, it looks like what you're proposing is an extended version of Proxy, no .... ?

Maybe, no idea what Proxy does.

'opDispatch' will work for simple cases, and in situations like
the one you described, where you just want a bit of sugar for a
/local/ always-on invariant, have full control over the wrapped
type, and want to eliminate the boilerplate that would otherwise
be required.

A more generic solution would be something like:

   struct EnforceWrapper(T) {
      T t;
        
      mixin wrapMembers!t;

      void _before(string M, A...)() {...}
      void _after(string M, A...)() {...}
   }

where the 'wrapMembers` mixin-template examines 't' and generates
the necessary wrappers. That way overload sets will keep working, etc.

artur