An approximation of "capture-by-clone" lambdas in Rust.
Requires nightly and #![feature(proc_macro_hygiene, stmt_expr_attributes)]
Turns this:
#[clown] || do_call(honk!(foo.bar))into this:
{
let __honk_0 = (foo.bar).clone();
move || do_call(__honk_0)
}