Dynamic/runtime checks (and crashes) are VERY different from compile time checks though. Many applications, and especially those that DARPA are focused on, care about ahead-of-time guarantees that code will work correctly, and runtime panic is actually the worst possible failure mode. Think of flight control software, for example.
And more comprehensively. There’s no `unsafe` statement in Fil-C. There’s no need for it since dynamic checking is vastly more precise.