Throw an exception but "hide" the top frame?

[ketmar via Digitalmars-d-learn]

On Wed, 24 Dec 2014 14:04:50 +0000
aldanor via Digitalmars-d-learn <digitalmars-d-learn at puremagic.com>
wrote:

> On Wednesday, 24 December 2014 at 13:48:26 UTC, ketmar via 
> Digitalmars-d-learn wrote:
> > the `object.Exception at wrap.d` is not a backtrace result, this 
> > is the
> > result of Exception class constructor:
> >
> >   this (string msg, string file=__FILE__, usize line=__LINE__, 
> > Throwable next=null)
> >
> > it registering the file and line of exception object creation in
> > COMPILE time. so you can do nothing with it, as there is no way 
> > to know
> > what called what in compile time.
> >
> > p.s. if you can use GDC, for example, and turn on debug info,
> > backtrace will show you files and line numbers for every 
> > address.
> 
> Hmm, that makes sense. After some pondering, I think I've hacked 
> together a workaround though:
> 
>      template check(alias func) {
>          auto check(string file = __FILE__, int line = 
> __LINE__)(int x) {
>              auto result = func(x);
>              if (result < 0) // throw on negative return vaule
>                  throw new Exception("%d < 0".format(result), 
> file, line);
>              return x; // otherwise, pass the result through
>          }
>      }
> 
> which produces:
> 
>      2
>      object.Exception at wrap.d(23): -3 < 0
>      ----------------
>      .. (_Dmain+0x20) [0x448de4]
> 
> 
> Are there any hidden downsides to doing it this way (aside from 
> generating additional code on every call)?

template bloat. now compiler can't use one instance of parameterized
template function for each call, but has to generate new template each
time.
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