Jai is a perfect example of how fashion dictates programming language popularity. The language isn't even released yet and people are mentioning it as the next great thing. If it wasn't for Jonathan Blow's successful indie games nobody would bat an eye.
That being said, I've got huge respect for the guy. I asked him about Nim in one of his streams and his reply was very courteous and reasonable.
I kind of wonder why everybody is so negative about me posting JAI here. I mean, yes the compiler isn't released yet, but that's why I wrote 'upcoming'.
You write about the 'next great thing', but I was merely talking about 'a better C++ for game development', which narrows it down to a very specific use-case. And I don't know what is wrong about if someone has had some success by building games to also look at the tools he uses for building those?
Besides that, looking at the few examples I have seen I didn't find the languages elegant, but it seems like it got inspired by some other modern languages like Go (e.g., no parentheses for if statements) while explicitly rejecting other ideas like the GC.
Many programming languages seem as though they are designed to force the programmer to be "safe", Rust's borrow checker is an example, but so is basically every GC-language ever. What Jon means by "designed for good programmers" is that the language design doesn't have this mindset that it needs to prevent the programmers from harming themselves, and instead focuses on allowing people who know what they're doing to be more productive doing it.
In JAI you own the code, the data, the build system, everything. JAI runs at compile time, so you can introspect your code and generate custom builds or generate custom files, or structures, like dictionaries of similarly named functions.
JAI doesn't implement abstractions (like objects or a GC) that might get in your way. JAI supports gradual refactoring and you can change your mind about the way memory is layed out ("AOS" (structs of arrays), delegates), and still use the same code. Want to shoot yourself in the foot with uninitialized variables? Fine!
In general, if you know what you are doing, JAI will allow it. JAI is similar to C in spirit, but C is a rather poor implementation in comparison.
Doesn't even try to prevent mistakes that a good programmer would avoid anyway.
For instance, C++ has operator overloading, which when misused leads do horrible, unreadable code. Still, the feature can be useful in some cases (vector/matrix library comes to mind). Java on the other hand avoids this feature because it doesn't trust the programmers with it.
As for JAI, it mostly means Jonathan Blow and his peers. I mean, he's obviously making a language for himself and whoever he hires. There's no point in catering to a different, wider audience. (The reason there's no point is because he doesn't need a whole ecosystem to support his language. He's trying to make it worth the effort even if he was the sole user.)
Its purpose is to become a better C++ for game development (high performance, simplicity).