On the subject of error messages

[Stanislav Blinov via Digitalmars-d]

On Tuesday, 16 May 2017 at 09:04:32 UTC, Nick Treleaven wrote:

> ...
>>>    foreach(i, T; types!args) {
>
> typeof(args) ;-)

Thanks :)

>>>        static if (is(T == string)) {
>>>            pragma(msg, format!"Argument %d is a string, which 
>>> is not supported"
>>>                    (i+1));
>
> The problem with this approach is all the work required to 
> convert existing code to use this style. Breaking the binary 
> ops of the constraint into parts and reporting which failed (as 
> the other replies mention) already would work with existing 
> code, even if your approach can allow better messages. The 
> binary ops part would immediately bring a huge improvement, 
> despite any deficiencies.

That's not a problem. In cases where compiler-provided diagnostic 
is sufficient, nothing will need to be done.

>
> I think we should allow inline constraints*, non-inline 
> constraints can still be used/combined. Inline constraints are 
> easier to read and relate to what they affect, allowing any 
> non-inline constraint to be considered as something with a 
> wider scope (i.e., multiple arguments).

No matter if it's inline or trailing, it needs way, *way* better 
reporting than what we have now, so if you were to prioritize, 
which one would you solve first? :)