D's greatest mistakes

[Simen kjaeraas]

Andrej Mitrovic <andrej.mitrovich at gmail.com> wrote:

>> Which error message should I show?
>>
> I'm not sure what you're getting at. :)
[snip]
> But anyway it's just an idea and I'm probably missing something
> important, I haven't used D in a while..

I believe you are missing that more templates could bear the same
name, and they could all fail for varying reasons. In such a case,
do you print the error messages from 100 templates and let the
user sort through them, or do you show the error the compiler
currently shows?

I admit my example was flawed, or at least incomplete:

> void foo( A )( A a )
> constraint {
>    isBar!A;
> }
>
> void foo( B )( B a )
> constraint {
>    isQux!B;
> }

void main( ) {
     int n;
     assert( !isBar!int );
     assert( !isQux!int );
     foo( n );
}

The call to foo would match neither template, giving errors akin
to this:

test.d(15) Error: template instantiation foo!int failed.
test.d(3)   Error: template constraint failed
test.d(6)   Error: template constraint failed

Seems good for two or three templates, but I fear this would grow
quickly out of hand for more templates.

-- 
Simen