ct-austin

It turns out we can write a proc macro to do this now: https://crates.io/crates/ifmt. Only works on nightly with `#![feature(proc_macro_hygiene)]`, but once proc macros are allowed in expression position it...

@lzutao That RFC is only for implicit capture of identifiers, supporting `format!("{foo}")` but no expressions beyond that. I think this RFC should be used to discuss potential expansions to expression...