[Rust] flexbuffers::Buffer trait, how to get zero-copy fn buffer_str?

[juliusl]

The trait requires Deref<Target = [u8]> however the trait defines fn buffer_str(&self) which is fine for the &'de [u8]'s implementation to get zero-copy since it's & &'de [u8], but this makes it really difficult for other types to implement Buffer since all types already implement Deref<Target = T> for &T which means you can't implement Deref<Target = [u8]> for &T.

I feel it would make more sense if it was something like this,

struct Example(bytes::Bytes);

trait TestBuffer {
    type BufferString<'s> where Self: 's;

    fn buffer_str<'a: 'b, 'b>(&'a self) ->  Result<Self::BufferString<'b>, std::str::Utf8Error>;
}

impl TestBuffer for Example {
    type BufferString<'s> = &'s str;

    fn buffer_str<'a: 'b, 'b>(&'a self) -> Result<Self::BufferString<'b>, std::str::Utf8Error> {
        std::str::from_utf8(self.0.as_ref())
    }
}

Playground link: https://play.rust-lang.org/?version=stable&mode=debug&edition=2021&gist=70cfeef51c776bdf836f02ef2ad1aaf7

Am I missing another way to get a zero-copy buffer_str() for custom Buffer implementations?

[juliusl]

So the only other way I've figured out how to do this w/ something like Bytes is by using unsafe code,

 fn buffer_str<'a: 'b, 'b>(&'a self) -> Result<Self::BufferString<'b>, std::str::Utf8Error> {
        unsafe {
            let slice = std::slice::from_raw_parts(self.0.as_ref().as_ptr(), self.0.len());
                    
            Ok(std::str::from_utf8(slice)?)
       }
}