Macro holmes::clause

macro_rules! clause {
    ($holmes:ident, $vars:ident, $next:ident, $pred_name:ident($($m:tt),*)) => { ... };
    ($holmes:ident, $vars:ident, $next:ident, $pred_name:ident{$($field:ident = $m:tt),*}) => { ... };
}