Awesome warning for named arg clash with named tuple

[som-snytt]

Backport #21565

Not sure of the correct workflow to get this on LTS.

I got ambitious and added a proper error ID, which will need to show up on HEAD, where it might go unused.

[hamzaremmal]

Why should this be backported to LTS ? Named tuple will never be on LTS 3.3.x and I'm not sure we want to add warnings to a feature that is already available in 3.3.0, 3.3.1, 3.3.3 and 3.3.4

We should focus imho on #21565 instead

[Gedochao]

cc @prolativ

[SethTisue]

Perhaps it should only warn under -source:future?

[hamzaremmal]

Perhaps it should only warn under -source:future?

I don't recall we've ever backported this kind of changes to 3.3.x. Why do it now and not for other changes ?

[SethTisue]

Upon reflection, I see that one can argue that although -source:future exists in Scala 3.3 LTS, it isn't especially important to maintain or improve it in an LTS series, since if someone really wants to know what a future compiler might have to say about their code, they can use an actual future compiler (Scala Next) to find out.

But that's not a reason not to do a straightforward backport. I'm just saying, the stakes seem low either way 🤷

Not sure of the correct workflow to get this on LTS.

The workflow is, you don't submit an explicit backport (well-meaning as such PRs obviously are — thank you!). Instead, add the "backport:nominated" label the original PR (or ask that it be added). Then it will be handled in the next wave of mass-backporting, when PRs are backported in merge order, to make the overall merge process easier.

I thought the new page https://www.scala-lang.org/development/ might explain this, but it doesn't, I guess because that's an end-user-facing page primarily (as opposed to contributor-facing).

Hence, I am closing this PR but I am also adding the "backport:nominated" label to #21565.