error: unexpected end of macro invocation --> $DIR/issue-7970a.rs:6:5 | LL | macro_rules! one_arg_macro { | -------------------------- when calling this macro ... LL | one_arg_macro!(); | ^^^^^^^^^^^^^^^^ missing tokens in macro arguments | note: while trying to match meta-variable `$fmt:expr` --> $DIR/issue-7970a.rs:2:6 | LL | ($fmt:expr) => (print!(concat!($fmt, "\n"))); | ^^^^^^^^^ error: aborting due to 1 previous error