Rust cannot create ReadHalf/WriteHalf to implement custom tranports

To implement custom transports ("channels") looks like the intention is:

1. Optionally, `impl TIoChannel for XXX` providing a split()
2. Create `ReadHalf` and `WriteHalf` as passed to various `XXXProtocol::new()` associated functions

Problems is:

use thrift::transport::{
  TIoChannel,
  ReadHalf,
  WriteHalf,
};

impl TIoChannel for TNngChannel {
fn split(self) -> thrift::Result<(ReadHalf<Self>, WriteHalf<Self>)> where Self: Sized,
{
    //SNIP
    Ok((
    ReadHalf { handle: self },
    WriteHalf { handle: clone }
    ))
}

Results in:
error[E0451]: field `handle` of struct `thrift::transport::ReadHalf` is private
--> runng-thrift\src\nng_channel.rs:57:24

57 | ReadHalf { handle: self },
 
^^^^^^^^^^^^ field `handle` is private
 
To enable creation of custom tranports/channels need to be able to create `ReadHalf` and `WriteHalf` from outside the crate.