Macro tract_core::element_map

macro_rules! element_map {
    ($Name:ident, [$($type:ty),*], $expr:expr) => { ... };
    ($Name:ident, match $($type:ty => { $expr:expr }),*) => { ... };
    ($Name:ident, match $($type:ty => $to:ty { $expr:expr }),*) => { ... };
}