[Issue 17263] Issue diagnostic if mandatory template parameter is missing

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=17263

--- Comment #3 from Jonathan M Davis <issues.dlang at jmdavisProg.com> ---
LOL. I just ran into this issue again, wasted several minutes trying to figure
out what was wrong, finally figured it out, and then decided to open an
enhancement request. But voila, there's already one sitting here, and I
commented on it previously. Honestly, I'd guess that this is quite possibly the
dmd error message that would provide the most benefit in being improved. Maybe
it gets harder to diagnose correctly when there are multiple overloads and they
don't all necessarily have the same number of template arguments, but it at
least _seems_ like it should be straightforward to figure out that the problem
is probably the lack of a ! and indicate as much to the programmer, even if
it's just a suggestion rather than an indicator that that's definitely the
problem.

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