Macro destruct_eval_bind 

macro_rules! destruct_eval_bind {
    (@reqr $ctx:ident, $vv:ident, $var:ident) => { ... };
    (@reqr $ctx:ident, $vv:ident, $var:ident $($vars:tt)+) => { ... };
    (@reqr $ctx:ident, $vv:ident,) => { ... };
    (@no-rest $ctx:ident, $vv:ident) => { ... };
    (@rest $ctx:ident, $rest:ident $vv:ident) => { ... };
    (@optvar $ctx:ident, $vv:ident, $var:ident) => { ... };
    (@optvar $ctx:ident, $vv:ident, $var:ident $($vars:ident)+) => { ... };
    (@impl $ctx:ident, ($($vars:ident)+) = $vv:ident) => { ... };
    (@impl $ctx:ident, ($($vars:ident)* &optional $($optvars:ident)+) = $vv:ident) => { ... };
    (@impl $ctx:ident, ($($vars:ident)* &rest $rest:ident) = $vv:ident) => { ... };
    (@impl $ctx:ident, ($($vars:ident)* &optional $($optvars:ident)+ &rest $rest:ident) = $vv:ident) => { ... };
    ($ctx:ident, ($($rest:tt)*) = $vv:ident) => { ... };
}