I've got my eye on Cpp2... Herb says he isn't interested in making it an official language but I suspect that once it stabilizes it will be an attractive migration.
Herb doesn't even want to default to immutable local variables (what he as a C++ person calls "const by default"). Obviously Cpp2 isn't finished enough for this to necessarily jump out, but Herb figures if we make a variable then we must intend to vary it, which is one of those claims I expect from newbie C++ programmers keen to defend their new language.
No, come on Herb, Kate Gregory has told us why there are variables, they are names for things. The machine doesn't need names, but the human maintenance programmers do. As a Microsoft employee I'm going to hazard a guess that Herb spends a lot less time staring at C++ real humans wrote before they died/ retired/ got fired without notice than Kate does in her consulting job. She knows what she's talking about.
I'm honestly not convinced that immutability for local variables is a particularly useful feature. Within the scope of a single function, it's usually pretty easy to see if a variable is being reassigned or not; there aren't the same kind of programming-in-the-large preventing-spooky-action-at-a-distance benefits that come from immutability across API boundaries. You increase the language's complexity and learning curve, for a benefit that's rather speculative and unclear.
(The exception is closures; prohibiting a variable from being reassigned after it's been closed over is useful because anyone reading the code may expect one of two conflicting behaviors depending on context, and so it's good to instead write the code in a way that doesn't have that ambiguity. Java got this one right.)
A post articulating this point, by the person primarily responsible for Rust's shared-xor-mutable architecture (so presumably he has some idea what he's talking about, though note that his argument did not carry the day): https://smallcultfollowing.com/babysteps/blog/2014/05/13/foc...
Notice that what you're asking for is to abolish const local variables. Which also isn't what Herb offers, this was the status quo in C during the K&R era because "const" didn't exist in K&R C. If you actually want const local variables, just not by default, you're not actually agreeing with Niko.
But then you have Google with Carbon… which is a direct competitor to cpp2. Apple hasn’t shown interest in either, and MS will of course most likely support cpp2.
Without the giants aligning their interests I’m afraid there will be a split in the community. Clang’s std C++ library is already behind GCC’s because Apple and Google have “moved” on.
Everything starts somewhere. I believe Chandler Carruth is leading the project so that means non-trivial resources are being dedicated to it. Their timeline is also fairly aggressive.
They're also simultaneously looking at Rust as a possible successor to C++ (e.g., by developing better interop tooling). It's believed that at most one of these projects can succeed in the long term.
