Missing method errors using AsyncRead

[chmln]

This may not be the correct place to post this, but I am running into weird errors trying to use AsyncRead.

Here is a narrowed down snippet illustrating the error (also uploaded at https://github.com/chmln/fut-err):

use futures;

pub struct LineStream<T: futures::io::AsyncRead> {
    inner: T,
}

impl<T: futures::io::AsyncRead> LineStream<T> {
    pub fn new(inner: T) -> Self {
        inner.poll_read();
        Self { inner }
    }
}

Error:

error[E0599]: no method named `poll_read` found for type `T` in the current scope
 --> src/main.rs:9:15
  |
9 |         inner.poll_read();
  |               ^^^^^^^^^
  |
  = help: items from traits can only be used if the trait is implemented and in scope
  = note: the following trait defines an item `poll_read`, perhaps you need to implement it:
          candidate #1: `futures_io::if_std::AsyncRead`

error: aborting due to previous error

Based on the suggestion I've tried adding std and nightly feature flags but that did not help either.

Extra Info:

$ rustc +nightly --version
rustc 1.36.0-nightly (3c3d3c177 2019-04-17)

[dependencies]
futures-preview = { version = "0.3.0-alpha.14" }

[Nemo157]

This is because poll_read takes self: Pin<&mut Self>, you need to explicitly wrap inner into a pinned reference (unlike &mut self etc. this is not done automatically by Rust):

core::pin::Pin::new(&mut inner).poll_read(unimplemented!(), unimplemented!());

This is a pretty terrible error message for forgetting that though, I'll make sure there's an upstream issue about improving the error message to mention the expected type.

[taiki-e]

This is a pretty terrible error message for forgetting that though, I'll make sure there's an upstream issue about improving the error message to mention the expected type.

rust-lang/rust#59269

EDIT: Oh, I was thinking about the compiler mentioning private modules, but it's really great to improve arbitrary self types' error message.

[Nemo157]

Opened rust-lang/rust#60086

[chmln]

Thanks for clearing that up @Nemo157 👍