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

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).