1error: expected string literal
2  --> $DIR/concat-display.rs:8:17
3   |
48  |         #[error(concat!("invalid ", $what))]
5   |                 ^^^^^^
6...
713 | error_type!(Error, "foo");
8   | -------------------------- in this macro invocation
9   |
10   = note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)
11