is_chan(def)bool
chan_dir(def) string (direction, send, recv, both)
chan_def(def) def

Some dependencies, such as atomic or parking_lot have nightly features that it would be good to enable and benefit from when enabling Metered's own nightly feature, for instance using const fns or simply benefitting from performance improvements in nightly dependencies.

It should be possible to change

balance <- function(tree) {
  match(tree,
        T(B,T(R,a,x,T(R,b,y,c)),z,d) -> T(R,T(B,a,x,b),y,T(B,c,z,d)),
        T(B,T(R,T(R,a,x,b),y,c),z,d) -> T(R,T(B,a,x,b),y,T(B,c,z,d)),
        T(B,a,x,T(R,b,y,T(R,c,z,d))) -> T(R,T(B,a,x,b),y,T(B,c,z,d)),
        T(B,a,x,T(R,T(R,b,y,c),z,d)) -> T(R,T(B,a,x,b),y,T(B,c,z,d)),
        otherwise -> tree)
}