1error: expected string literal
2  --> tests/ui/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 the macro `error_type` (in Nightly builds, run with -Z macro-backtrace for more info)
11