warning: unused imports: `cell::RefCell`, `collections::VecDeque`, `rc::Rc`
 --> problems/traits/mpsc/src/lib.rs:3:11
  |
3 | use std::{cell::RefCell, collections::VecDeque, fmt::Debug, rc::Rc};
  |           ^^^^^^^^^^^^^  ^^^^^^^^^^^^^^^^^^^^^              ^^^^^^
  |
  = note: `#[warn(unused_imports)]` on by default

error[E0392]: parameter `T` is never used
  --> problems/traits/mpsc/src/lib.rs:18:19
   |
18 | pub struct Sender<T> {
   |                   ^ unused parameter
   |
   = help: consider removing `T`, referring to it in a field, or using a marker such as `PhantomData`
   = help: if you intended `T` to be a const parameter, use `const T: usize` instead

error[E0392]: parameter `T` is never used
  --> problems/traits/mpsc/src/lib.rs:63:21
   |
63 | pub struct Receiver<T> {
   |                     ^ unused parameter
   |
   = help: consider removing `T`, referring to it in a field, or using a marker such as `PhantomData`
   = help: if you intended `T` to be a const parameter, use `const T: usize` instead

   Compiling mio v0.8.0
For more information about this error, try `rustc --explain E0392`.
warning: `mpsc` (lib) generated 1 warning
error: could not compile `mpsc` due to 2 previous errors; 1 warning emitted
warning: build failed, waiting for other jobs to finish...
warning: `mpsc` (lib test) generated 1 warning (1 duplicate)
error: build failed