macro_rules! impl_metric_label {
($visibility:vis enum $label:ident { $($variant:ident => $value:tt),+ $(,)? }) => { ... };
($label:ty { $($variant:ident => $index:expr),+ $(,)? }) => { ... };
}macro_rules! impl_metric_label {
($visibility:vis enum $label:ident { $($variant:ident => $value:tt),+ $(,)? }) => { ... };
($label:ty { $($variant:ident => $index:expr),+ $(,)? }) => { ... };
}