Accessing args for a parsed ICU string

I am writing a wrapper for string formatting, so that a string like `There are {foo} apples.` with an identifier `some_string` can be accessed like so in Rust:

```rust
pub fn some_string(foo: &str) -> String {
...
}
```

Right now it does not seem possible to access Args from anywhere because they are not attached to any struct but generated on the fly by a macro.

What is the suggested course of action for getting access to the Args at the moment? I don't mind if it's a bit round-about, as it will only be used from a build.rs script. Thanks!