machine::transitions_impl!

macro_rules! transitions_impl {
    ($machine:ident, $state:ident, {$($field : ident),*}, ) => { ... };
    ($machine:ident, $state:ident, {$($field : ident),*}, $name:ident ( $( $arg:ident : $t:ty ),* ) => $next:ident $b:block; $($rest:tt)* ) => { ... };
    ($machine:ident, $state:ident, {$($field : ident),*}, $name:ident => $next:ident; $($rest:tt)* ) => { ... };
    ($machine:ident, $state:ident, {$($field : ident),*}, $name:ident => $next:ident $b:block; $($rest:tt)* ) => { ... };
}