[tekknik]

I’m not a rust programmer, reading your explanation here it’s not anymore clear why some macros exist (println for instance). They very much look similar to functions in most of the cases I’ve seen (again from the perspective of trying to find a reason besides safety to learn rust) so why exactly do these exist? They are a great source of confusion for those of us with C/C++ experience (or at least me) which is the target audience.

[DesertVarnish]

println is a macro in Rust because 1) the language currently lacks support for variadic functions and 2) being a macro allows the format string to be parsed at compile time.

[eddyb]

Long-term, with const generics, and VG (or a macro that creates a (a, (b, (c, ()))) nesting like the hlist crate), we could maybe replace format_args! and friends.

However, there is one more thing a function can't do: borrowing arguments. Formatting never moves arguments because the format_args! macro generates references to them, which it then creates std::fmt::Argument out of.