1586 – DMD and GDC segfaults on incomplete code segment.

Hello,
A typo revealed a way to make the compiler segfault. Trying to compile the following incomplete code segment as a complete module causes the official D compiler (versions 1.022 and 2.005) and GDC 0.24 to segfault.
////////////
module badcode;
void myFunc()
{
 auto func = &NotHere!(1).Bar!(k); // NotHere is not defined.
}
/////////////
Thanks!
--Hoyt

Added to DStress as
http://dstress.kuehne.cn/nocompile/t/template_66_A.d
http://dstress.kuehne.cn/nocompile/t/template_66_B.d
http://dstress.kuehne.cn/nocompile/t/template_66_C.d
http://dstress.kuehne.cn/nocompile/t/template_66_D.d
http://dstress.kuehne.cn/nocompile/t/template_66_E.d 

The segv is in this code:
Expression *DotTemplateInstanceExp::semantic(Scope *sc)
...
 if (!s2)
 { error("template identifier %s is not a member of %s %s", id->toChars(), s->kind(), s->ident ? s->ident->toChars() : "(null)");
 goto Lerr;
 }
...
s->ident is null, so s->ident->toChars() is invalid. I added the ?: expression to validate that, and here's the resulting error message: 
/home/braddr/sandbox/d/bugs/bug1586.d:5: template instance identifier 'NotHere' is not defined
/home/braddr/sandbox/d/bugs/bug1586.d:5: Error: template identifier Bar is not a member of template instance (null)
My fix is wrong, but hopefully this will save Walter a few minutes of narrowing down.

While I enjoy another fix:
 if (!s2)
 {
 if(s->ident) 
 error("template identifier %s is not a member of %s %s", id->toChars(),
s->kind(), s->ident->toChars() : "(null)");
 goto Lerr;
 }
Since the Template Instance is unknown so this error message is useless.

Fixed in DMD2.028; not yet in D1.

Fixed DMD2.028 and 1.045.