在 rust 中返回没有泛型参数的泛型类型

Question

I have a code where I want to create a wrapper around a library to make it work in the same philosophy as the rest of my code. To avoid writing hundreds of structs I am creating a generic one (Worker). But I am using the function to configure it and I pass that information as an enum:

fn configure(config: Config) -> Worker<T> {
    match config {
        some_config => Worker<some_type>,
        _ => {...}
}

As I am already passing the information as an enum I want to avoid passing a type argument to the function but obviously rust complains because T is not defined.

Is there a way to make rust infer the type of the return generic of something? I've though of using a macro too but I don't know if it's the right solution. Any idea of how to solve this? Thank you in advance for your time!

Answer 1

If I understand correctly, the concrete type for T will be different depending on what was passed in the enum.

You can't do that with generics though. For any concrete type that's filled in for T , each branch of a function needs to return the same type. You can't have a function that, based on some enum or if statement returns, say, a Vec<String> versus a Vec<u32> .

Ways around that: Wrap them in an enum, too.

Or use traits instead of generics. Then your function can return, for example, a Box<dyn Worker> and Worker is a trait.