1 error: cannot find attribute `unknown` in this scope
2 --> $DIR/cfg-attr-unknown-attribute-macro-expansion.rs:3:27
4 LL | #[cfg_attr(all(), unknown)]
8 | ------ in this macro invocation
10 = note: this error originates in the macro `foo` (in Nightly builds, run with -Z macro-backtrace for more info)
12 error: aborting due to previous error