Producing nicer template errors in D libraries

[Jacob Carlborg]

On 2012-04-10 21:45, H. S. Teoh wrote:
> A lot of template code (e.g. a big part of Phobos) use signature
> constraints, for example:
>
> 	void put(T,R)(R range, T data) if (isOutputRange!R) { ... }
>
> This is all nice and good, except that when the user accidentally calls
> .put on a non-range, you get reams and reams of compiler errors
> complaining that certain templates don't match, certain other
> instantiations failed, etc., etc.. Which is very unfriendly for newbies
> who don't speak dmd's dialect of encrypted Klingon. (And even for
> seasoned Star Trek^W^W I mean, D fans, it can take quite a few seconds
> before the real cause of the problem is located.)

Original I would have gone with something like:

struct OutputRange
{
     void foo ();
     void bar ();
}

void put(T,OutputRange R)(R range, T data)

Or:

void put(T,R : OutputRange)(R range, T data)

Something like that.

-- 
/Jacob Carlborg