1 error: 1 positional argument in format string, but no arguments were given
2 --> $DIR/macro-backtrace-println.rs:14:30
4 LL | ($fmt:expr) => (myprint!(concat!($fmt, "\n")));
8 | ----------------- in this macro invocation
10 = note: this error originates in the macro `concat` (in Nightly builds, run with -Z macro-backtrace for more info)
12 error: aborting due to previous error