Making a wrapper type implementation generic - rust

Question

I have the following wrapper type (similar to std::io::Cursor) to allow limiting the number of bytes read:
use std::{cmp, io};
pub struct Limited<T> {
inner: T,
pos: u64,
limit: u64,
}
impl<T> Limited<T> {
pub fn new(inner: T, limit: u64) -> Limited<T> {
Limited {
inner: inner,
pos: 0,
limit: limit,
}
}
pub fn pos(&self) -> u64 { self.pos }
pub fn limit(&self) -> u64 { self.limit }
pub fn into_inner(self) -> T { self.inner }
pub fn get_ref(&self) -> &T { &self.inner }
pub fn get_mut(&mut self) -> &mut T { &mut self.inner }
}
impl<T: io::Read> io::Read for Limited<T> {
fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
let can_read = cmp::min(buf.len() as u64, self.limit - self.pos);
if can_read != 0 {
match self.inner.read(&mut buf[..(can_read as usize)]) {
Ok(read) => {
self.pos += read as u64;
Ok(read)
},
e # _ => e
}
} else {
Ok(0)
}
}
}
Then I can use it like this:
let mut l = Limited::new(io::Cursor::new(vec![1, 2, 3]), 1);
assert_eq!(l.read(&mut [0; 10]).unwrap(), 1);
Next I need to have Limited<RefMut<Read>> (so it owns the RefMut). Adding impl<'a, T: 'a + io::Read> io::Read for Limited<RefMut<'a, T>> makes the compiler complain about conflicting implementations.
Is there a way to have a generic implementation of Limited that would work for Read, RefMut<Read>, Rc<Read>, DerefMut<Target=Read>?

Answer 1

Is there a way to have a generic implementation of Limited that would work for Read, RefMut<Read>, Rc<Read>, Deref<Target=Read>?
Not really.
Read and DerefMut 1 are both traits. What should the expected behavior be if you passed in a type that implemented both traits? There's a RFC for specialization that might allow this in some form or the other. As the name says, it's usually about a more specific implementation, so I don't know how two distinct traits would fit in.
RefMut already implements DerefMut, so presumably that would be covered. I don't know how Rc would come into play as it's only for immutable data.
1: I assume you mean DerefMut instead of Deref as Read needs a mutable receiver.