Fix Issue 18960 - Function parameter requires name with default value

[sorin-gabriel]

Closing the issue by adding clarifications in the spec. The behaviour mentioned in the issue actually seems reasonable (so it's not a bug), but the docs don't mention this anywhere.

[dlang-bot]

Thanks for your pull request and interest in making D better, @sorin-gabriel! We are looking forward to reviewing it, and you should be hearing from a maintainer soon.
Please verify that your PR follows this checklist:

• My PR is fully covered with tests (you can see the coverage diff by visiting the details link of the codecov check)
• My PR is as minimal as possible (smaller, focused PRs are easier to review than big ones)
• I have provided a detailed rationale explaining my changes
• New or modified functions have Ddoc comments (with Params: and Returns:)

Please see CONTRIBUTING.md for more information.

---

If you have addressed all reviews or aren't sure how to proceed, don't hesitate to ping us with a simple comment.

Bugzilla references

Your PR doesn't reference any Bugzilla issue.

If your PR contains non-trivial changes, please reference a Bugzilla issue or create a manual changelog.

[rikkimax]

After reviewing my ticket, I cannot place what exactly I was referencing in the spec. I should have linked it.

Therefore I'm going to close it as invalid because I'm pretty sure I miss interpreted something related to function parameters.

However your example is good, just drop the reference to the ticket.