[logicchains]

Writing this kind of async code in Haskell (and to some extent OCaml) is much nicer, because you can abstract over the asyncness of code. This can't be done in Rust or C# because the type system isn't powerful enough (no higher-kinded types). To be fair, adding HKTs to Rust's existing type system is a challenging theoretical problem in itself.

[pjmlp]

C++ surely has HKT, that is what templates that take other templates as type parameters are for.

[tialaramex]

In a sense, but the "ill-formed, no diagnostic required" hack allows for scenarios where what you wrote is nonsense, and a human can explain why, but your C++ compiler doesn't have that insight, so it compiles anyway and does... something. This avoids needing to teach the machine how to determine if what you did was sound.

But this is of course not a very safe way to write software.

[pjmlp]

If the author is fool enough to not use the language features that exist since C++17 to validate template code, surely.

I also don't find debugging Rust macros that fun, yet most likely the answer will be that the macro author didn't took enough care, and Rust is great to write gigantic DSL macros.

[tialaramex]

> If the author is fool enough to not use the language features that exist since C++17 to validate template code, surely.

To be sure the fact the diagnostics aren't required does not forbid them from being provided, but it does mean you'd need to know whether you've been provided with such diagnostics and how effective they actually are. Unless the answer is "I have diagnostics and they are 100% effective" you're in the same situation.

> I also don't find debugging Rust macros that fun

Which kind? I don't find debugging the declarative macros too hard, they are after all just expanding what you wrote according to some simple rules, and you can ask the compiler to show that expansion to you.

Procedural macros present unlimited potential for exciting debugging because now you're essentially modifying the compiler at runtime. A C++ pre-processor macro can cause some nasty problems but it's not going to run a different compiler... [Technically Mara's nightly-crimes only runs the same compiler with different flags, but it could run a different one if she'd needed to do that]

[andrepd]

Sure, but the exchange is that you get worse performance.