If someone wants to propose a way to handle RFC 2795 in defmt, I'm all ears. I've thought about it, and I concluded it was pretty tricky.

On std, format!("Hello {x}!") becomes something very roughly like:

```rust
let f = FormatStuff {
    string_pieces: &["Hello ", "!"],
    data_pieces: &[&x],
    format_pieces: &[format_int]
};
```

That is, the string does not survive intact. It is broken into pieces and formatting functions are executed part way through.

If you defer formatting, the string must (currently) be delivered intact. If a string contains `{x}`, then which argument in the pile of bytes that follows the string is x?

If someone can write a project macro that turns `"Hello {x}!"`, into `"Hello {0=usize}!", x`, then that would be great. I don't think I know how to do that.