error[E0426]: use of undeclared label `'x` --> $DIR/hygienic-label-3.rs:2:19 | LL | () => { break 'x; } | ^^ undeclared label `'x` ... LL | foo!(); | ------ in this macro invocation | = note: this error originates in the macro `foo` (in Nightly builds, run with -Z macro-backtrace for more info) error: aborting due to previous error For more information about this error, try `rustc --explain E0426`.