Feature Request: Location of template instantiation failure

[Bill Baxter]

Janice Caron wrote:
> Consider the following code
> 
>     import std.stdio;
> 
>     int f(int N)(int x)
>     {
>         static assert(N >= 0 && N < 10); // line 5
>         return N + x;
>     }
> 
>     void main()
>     {
>         writefln(f!(3)(3));
>         writefln(f!(13)(1)); // line 12
>         writefln(f!(7)(2));
>     }
> 
> It won't compile. This is correct. I don't want it to compile.
> 
> What concerns me is that there's no way to locate the real error. The
> error message which the compiler emits is:
> 
> 	test.d(5): static assert  is false
> 
> There is indeed a static assert on line 5, and for ONE of the
> instantiations it comes out false. But the /real/ error is on line 12,
> where I pass an invalid parameter to the template. The compiler
> doesn't tell me that.
> 
> So ... feature request: If the DMD compiler is unable to instantiate a
> template, then, as part of the error reporting, please could it print
> out the filename and line number of the line which triggered the
> instantiation? It would be so much more helpful to see:
> 
>     test.d(5): static assert  is false
>     test.d(12): instantiation failure
> 
> or similar.

Amen to that.  We need template instantiation stack traces.  Thanks to 
Jascha and ddbg we can now get the run-time stack traces easily, but 
we're still up a creek with nothing but a couple of toothpicks when it 
comes to tracking down the source of compile-time template errors.

--bb