Fix issue 6251: docs should warn about foreach_reverse over delegate.

[quickfur]

Fixes: https://issues.dlang.org/show_bug.cgi?id=6251

[ghost]

Thanks!

[CyberShadow]

The compiler emits a warning when attempting to use foreach_reverse over a delegate:

dlang/dmd#184

[ghost]

But only with -wi right?

[CyberShadow]

Well, yes, since it's a warning.

[ghost]

I mean, the user may not be aware of it unless they have the switch enabled. So it's still nice to document intention.

[CyberShadow]

Yes. I thought I'd mention it since the problem is spread across two issues, the warning was committed after the documentation issue was opened, and this documentation change does not mention the warning.

[ghost]

So, another pull in the making? :)

[CyberShadow]

I don't know? This pull doesn't exactly contradict the warning pull.

[CyberShadow]

FYI Daniel posted a pull to change it to a deprecation:
dlang/dmd#3971

[quickfur]

The warning was committed but it's almost unnoticeable, since it only shows up with -w. I didn't even notice it until I saw the PR that implements it, and started wondering why the message wasn't been displayed -- I actually had to read the code before I realized that -w was necessary. Tl;dr, the effectiveness of the warning is close to nil. I support the PR to turn it into a deprecation.