Matching String for Debug and Release Build in Rust

Question

Assuming I have an &str named myvar which I somehow get from environment variables. I can match it as below:

match myvar {
    "foo" => todo!(),
    "bar" => todo!(),
    _ => todo!(), // if an unexpected value
}

I also can know if the compiled app is debug or release build via cfg!(debug_assertions).

Now, what I want is provide a fallback value for this &str but it should differ whether the binary is a debug build or not. So:

match myvar {
    "foo" => todo!(),
    "bar" => todo!(),
    _ && cfg!(debug_assertions) => todo!(), // fallback in debug build
    _ => todo!(), // fallback in release build
}

Is such a thing possible?

Thanks in advance.

Answer 1

The thing you're looking for is likely to be the match guards. General syntax for them is as following:

match value {
   pattern if conditional = todo!(),
   // other branches
}

In your case, this is a simple change:

match myvar {
    "foo" => todo!(),
    "bar" => todo!(),
    _ if cfg!(debug_assertions) => todo!(), // fallback in debug build
    _ => todo!(), // fallback in release build
}