Macro emacs_module_bindings::emacs_subrs

macro_rules! emacs_subrs {
    ($($name:ident($env:ident, $nargs:ident, $args:ident, $data:ident, $tag:ident)
       $body:expr;)*) => { ... };
}

A μDSL to cut away boilerplate when defining Emacs subrs, which are of course defined in Rust rather than C here. One thing enforced at compile time is that some semblance of a legal Elisp value is returned.