Help me understand how to contribute to bugs report / fixing

[Fra Mecca]

Hi,
I have been lurking in the bug tracker for some time, checking 
and trying to reproduce bugs and fixes.

I finally want to submit something and contribute but I am having 
an hard time understanding the workflow.

Pull request are done via git and bugs reported by the tracker.
The problem is when I want to understand if the bug of the 
tracker is referenced in the repo of the organization and has an 
open PR.

---

Real world case:
this bug has been reported recently:
https://issues.dlang.org/show_bug.cgi?id=18288#add_comment

but it should be closed given how in the recent changes to the 
phobos master branch the bug is fixed. You can double check that 
by running the code snippet using dmd-nightly in run.dlang.io.

 From a quick glance at the phobos repo, I found no mention of 
this bug in any closed or open PR, just a PR (#6056, bug 18280) 
on the same file (comparison.d) that probably fixed the issue for 
bug 18288.

What should I do now?
I am undecided between:
- commenting on the bug tracker and close the bug
- link the pr 6056 on the bug tracker
- leaving it be

I feel that the section "Get involved" on the D wiki should aid 
newcomers with a more detailed description of the workflow of 
maintainers and collaborators.