Macro impl_dlc_writeable_enum 

macro_rules! impl_dlc_writeable_enum {
    ($st:ident, $(($tuple_variant_id: expr, $tuple_variant_name: ident)), *;
    $(($variant_id: expr, $variant_name: ident, {$(($field: ident, $fieldty: tt)),*})), *;
    $(($external_variant_id: expr, $external_variant_name: ident, $write_cb: expr, $read_cb: expr)), *;
    $(($simple_variant_id: expr, $simple_variant_name: ident)), *) => { ... };
}

Implements the lightning::util::ser::Writeable trait for an enum.