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> C++ also has 'constexpr if' FTR since 1.46.0, Rust also has if inside const contexts (as well as loop and match, but no for loops as they are trait based and

• cyber_kinetist 4y ago
  That isn't the same as 'constexpr if'. In C++ you can use 'constexpr if' even in non-constexpr/consteval contexts in order to control code generation, like for example: template<class T> auto foo() { if constexpr(compile_time_compute_value_changing_depending_on_T<T>()) { return Type1(); else { return Type2(); } } You can even change the return type of a function depending on the template parameter! Such is the power of duck-typed templates (as opposed to a strict trait system that Rust has)
  • est31 4y ago
    Oh I see that's a way different feature then, that Rust indeed doesn't have. You could in theory build a proc macro that supports a meta-language, but it would not be able interact with any of Rust's type system. Rust doesn't even allow _, the equivalent of auto, for return types of functions at all, even though it has a lot of type deduction (which is I think a good decision because it makes type deduction local, so you know which types you are dealing with by looking at the function header).