The case against a C alternative
> Any C alternative will be expected to be on par with C in performance. The problem is that C have practically no checks, so any safety checks put into the competing language will have a runtime cost, which often is unacceptable. This leads to a strategy of only having checks in "safe" mode. Where the "fast" mode is just as "unsafe" as C.<p>I don't think this is true, in the general case: Rust has shown that languages can be safe in ways that <i>improve</i> runtime performance.<p>In particular, languages like Rust allow programmers to express stronger compile-time constraints on runtime behavior, meaning that the compiler can <i>safely</i> omit bounds and other checks that an ordinary C program would require for safety. Similarly, Rust's (lack of) mutable aliasing opens up entire classes of optimizations that are extremely difficult on C programs (to the extent that Rust regularly exposes bugs in LLVM's alias analysis, due to a lack of exercise on C/C++ inputs).<p>Edit: Other examples include ergonomic static dispatch (Rust makes things like `foo: impl Trait` <i>look</i> dynamic, but they're really static under the hood) and the entire notion of a "zero-cost abstraction" (Rust's abstractions are no worse than their "as if" equivalent, meaning that the programmer is restricted in their ability to create suboptimal implementations).