Macro stackbox::stackbox

macro_rules! stackbox {
    (
        // `<binding> = stackbox!($expr);`
        // Examples:
        //   - `stackbox!(<expr> => let new_var);`
        //   - `let var; stackbox!(<expr> => var);`
        //   - `stackbox!(<expr> => let mut mutable_var);`
        $expr:expr => $($binding:tt)*
    ) => { ... };
    (
        // To be used as a temporary fed to a function parameter, or as a
        // `[::with_locals::with]` "return" value.
        $expr:expr
    ) => { ... };
}