// aux-build:format-string-proc-macro.rs #[macro_use] extern crate format_string_proc_macro; macro_rules! def_site { () => { "{foo}" } //~ ERROR: there is no argument named `foo` } macro_rules! call_site { ($fmt:literal) => { $fmt } } fn main() { format!(concat!("{foo}")); //~ ERROR: there is no argument named `foo` format!(concat!("{ba", "r} {}"), 1); //~ ERROR: there is no argument named `bar` format!(def_site!()); format!(call_site!("{foo}")); //~ ERROR: there is no argument named `foo` format!(foo_with_input_span!("")); //~ ERROR: there is no argument named `foo` }