No, you can just write D. It'll have the same performance as C, if you write C-like code. It might have better performance than C if you use templates (just like in C++).
Because it is also possible to write tests that don't adequately capture real-life requirements.
It was an MQTT server, and the tests basically went "if we have these subscriptions, then...", but no subscriptions ever got actually stored by the server.
I hear this about both Haskell and Rust, and yet, when I tried both in the former I wrote a useless program because I didn't handle state (and yet passed all tests!) while in the latter I immediately wrote a deadlock.
I made the same comment last week upon learning of a redis clone entirely vibe coded in IIRC ~70k lines of Rust. Why Rust? Why does a computer need a memory safe language?
Yes, I do.