The Right Approach to Exceptions

[Daniel Murphy]

"Jonathan M Davis" <jmdavisProg at gmx.com> wrote in message 
news:mailman.582.1329634661.20196.digitalmars-d at puremagic.com...
> On Sunday, February 19, 2012 16:59:49 Daniel Murphy wrote:
>> "Nick Sabalausky" <a at a.a> wrote in message
>> news:jhprac$2aj$1 at digitalmars.com...
>>
>> > The only problem I've ever had with them is that there's no templated
>> > catch blocks, so you can't handle two different exceptions with the 
>> > same
>> > code without violating DRY or worse: catching the common base type and
>> > rethrowing when it's not what you wanted. Toss in templated catch 
>> > blocks,
>> > and I've have no problem at all.
>>
>> Do you mean something like this?
>> try
>> {
>>     something();
>> }
>> catch (e : ThisException, ThatException, OtherException)
>> {
>>     static assert(is(typeof(e) == CommonType!(ThisException, 
>> ThatException,
>> OtherException));
>> }
>> catch (Exception e)
>> {
>>     // Every other type derived from Exception
>> }
>>
>> Or do you think the full power to be able to template catch blocks as if
>> they were functions would be useful for something?
>
> I think that being able to have a catch block which took multiple 
> exception
> types would be plenty. There are times when it would be very valuable to 
> be
> able to use the same catch block for multiple exceptions without having to
> catch their base type (which would then potentially catch other exceptions
> which you didn't want to catch). So, something like that second catch 
> block
> that you have there would be very valuable.
>
> - Jonathan M Davis

I assume you mean the _first_ catch block?

By the looks of it java 7 has this with an awful syntax.

Maybe we should introduce implicit 'catch fallthrough':

void fun()
{
    try { something; }
    catch (ExceptionA) {} // falls through implicitly
    catch (ExpcetionB)
    { // handle both A and B
        break;
    }
    catch (ExceptionC)
    {
        // handle exception C
        break;
    }
}