Numbering compiler error messages?

[Steven Schveighoffer]

On Sun, 30 Mar 2014 15:23:44 -0400, Walter Bright  
<newshound2 at digitalmars.com> wrote:

> On 3/30/2014 4:04 AM, Paulo Pinto wrote:
>> Am 28.03.2014 19:09, schrieb Walter Bright:
>>> On 3/28/2014 2:23 AM, monarch_dodra wrote:
>>>> Well, I'm just throwing that out there.
>>>
>>> I've thought many times that an error message should be a clickable
>>> link. But until console displays support clickable text, it's just a
>>> fantasy.
>>
>> Actually on GNU/Linux systems many do.
>
> I just tried it on Ubuntu and - you're right! Pretty awesome.

Yes, I think a url, even if not clickable, is way more useful than an  
arbitrary error id. It takes not much effort to copy/paste a URL into a  
browser.

We can make this easy:

Compiler outputs a URL like this: http://derror.org/2.065/filename.c/l123

Using a function that takes __FILE__ and __LINE__

Then, include a special comment just before the error output that will be  
parsed by a post-processor, and link that url to the comment (either in  
github, or on a nice web page).

Example:

const char *errurl(const char *file = __FILE__, int line = __LINE__); //  
does this work in C++? I can't remember!

// <ERRMSG> A variable cannot be re-defined inside a new scope. See  
http://dlang.org/...
error("is shadowing declaration %s%s", s->toPrettyChars(), errurl());

errurl could be configured to print a URL or nothing via a command line  
option.

Bonus: those who know the error url format know exactly where to go in the  
code to see where it was printed from.

-Steve