Upstream has followed several of opend's innovations: we shipped interpolated expressions on day one of the fork (that was the straw that broke the camel's back) and then, after 7 years of procrastination, upstream also merged it a week later. We shipped extern(Objective-C) support, upstream backported it (and actually fixed enough bugs that I replaced my original impl with their's) a few months later. Upstream has talked about "safe by default" for over nine years. We shipped "safer by default" as a compromise (full safe by default is too much of a breaking change) a few months after forking, then a few months after we shipped it, upstream announced their own "safer by default" switch (which you have to opt into, so they kinda missed the point of "by default" but still, they followed the overall concept). For basically ever, Walter has said null checks in the language were a hard no, we implemented them and then.... guess what, a few months later, my implementation was backported (and again, a few bugs fixed so i appreciate the collaboration when we can get it) and walter decided to allow the merge. Opend shipped druntime on webassembly, looks like something similar coming to upstream. We merged the tuple destructuring PR (that was open for years again so the author was happy to get it to land somewhere!) and upstream followed there too.

There's a lot of smaller things that haven't been pulled though, like i merged a bug fix to module naming, which was an upstream PR from like 2018, a fix on library file name generation, a regression from 2019 but has a trivial workaround, a fix to redefined reflection names which everyone finds annoying, the implementation was written in 2017, but they had endless debates about syntax and i just made an executive decision and moved on but they still bikeshed... stuff like that, they're all little things but minor annoyances every time you hit them and the fixes were easy, so just do it!

Then the two bigger things I did they have talked about but probably won't do is i made the class monitor opt-in, this is a relatively big breaking change, I had to do fixes on 8 different projects. Each one took a few minutes, so not a huge deal, but still. They talked about this in an upstream meeting but decided against taking it (for now at least).

And then I changed the default init of all built in types to zero, including char and float, and this is controversial since float init to nan has legitimate advantages, and the breakage can be subtle if you don't catch it. I was on the fence personally, it more like a 51-49 vote rather than an obvious bug fix, but it is easier to explain to newbies that int and float both init to 0. In theory, you are supposed to explicitly initialize all these all the time, but in practice we know it is different.

So I think the competitive edge is pushing them a little. And I'm not anti-collaboration; I write blogs about my implementations with the hope that they'll give a little code review and that's been semi-successful, like the upstream backporters have indeed fixed bugs in my implementations so I'm happy to share back and forth, we both win that way.