Macro batch_impl_open 

batch_impl_open!() { /* proc-macro */ }

Documentation placeholder for the open-extension protocol.

A #name(args){body} whose name is not a built-in directive expands to a call of a user-defined function-like macro of the same name, handed the args, body and trait definition: #my_ext(x){y} → { my_ext!{ (x) {y} trait_def } }.

macro_rules! my_ext { ($($rest:tt)*) => {}; }
#[batch_impl(Box<u32> #my_ext(x){y})]
trait O {}

Documentation marker only — never call this function.